Refactored tree / organic supports into multiple compilation modules.

src/libslic3r/CMakeLists.txt

@@ -288,8 +288,12 @@ set(SLIC3R_SOURCES
     Support/SupportMaterial.hpp
     Support/SupportParameters.cpp
     Support/SupportParameters.hpp
+    Support/OrganicSupport.cpp
+    Support/OrganicSupport.hpp
     Support/TreeSupport.cpp
     Support/TreeSupport.hpp
+    Support/TreeSupportCommon.cpp
+    Support/TreeSupportCommon.hpp
     Support/TreeModelVolumes.cpp
     Support/TreeModelVolumes.hpp
     SupportSpotsGenerator.cpp

src/libslic3r/Support/OrganicSupport.cpp

@@ -0,0 +1,992 @@
+#include "OrganicSupport.hpp"
+
+#include "AABBTreeLines.hpp"
+#include "ClipperUtils.hpp"
+#include "Polygon.hpp"
+#include "Polyline.hpp"
+#include "MutablePolygon.hpp"
+#include "TriangleMeshSlicer.hpp"
+
+#include "Support/SupportCommon.hpp"
+
+#include <cassert>
+
+#include <tbb/parallel_for.h>
+
+#define TREE_SUPPORT_ORGANIC_NUDGE_NEW 1
+
+#ifndef TREE_SUPPORT_ORGANIC_NUDGE_NEW
+    // Old version using OpenVDB, works but it is extremely slow for complex meshes.
+    #include "OpenVDBUtilsLegacy.hpp"
+    #include <openvdb/tools/VolumeToSpheres.h>
+#endif // TREE_SUPPORT_ORGANIC_NUDGE_NEW
+
+namespace Slic3r
+{
+
+namespace FFFTreeSupport
+{
+
+// Test whether two circles, each on its own plane in 3D intersect.
+// Circles are considered intersecting, if the lowest point on one circle is below the other circle's plane.
+// Assumption: The two planes are oriented the same way.
+static bool circles_intersect(
+    const Vec3d &p1, const Vec3d &n1, const double r1, 
+    const Vec3d &p2, const Vec3d &n2, const double r2)
+{
+    assert(n1.dot(n2) >= 0);
+
+    const Vec3d z = n1.cross(n2);
+    const Vec3d dir1 = z.cross(n1);
+    const Vec3d lowest_point1 = p1 + dir1 * (r1 / dir1.norm());
+    assert(n2.dot(p1) >= n2.dot(lowest_point1));
+    if (n2.dot(lowest_point1) <= 0)
+        return true;
+    const Vec3d dir2 = z.cross(n2);
+    const Vec3d lowest_point2 = p2 + dir2 * (r2 / dir2.norm());
+    assert(n1.dot(p2) >= n1.dot(lowest_point2));
+    return n1.dot(lowest_point2) <= 0;
+}
+
+template<bool flip_normals>
+void triangulate_fan(indexed_triangle_set &its, int ifan, int ibegin, int iend)
+{
+    // at least 3 vertices, increasing order.
+    assert(ibegin + 3 <= iend);
+    assert(ibegin >= 0 && iend <= its.vertices.size());
+    assert(ifan >= 0 && ifan < its.vertices.size());
+    int num_faces = iend - ibegin;
+    its.indices.reserve(its.indices.size() + num_faces * 3);
+    for (int v = ibegin, u = iend - 1; v < iend; u = v ++) {
+        if (flip_normals)
+            its.indices.push_back({ ifan, u, v });
+        else
+            its.indices.push_back({ ifan, v, u });
+    }
+}
+
+static void triangulate_strip(indexed_triangle_set &its, int ibegin1, int iend1, int ibegin2, int iend2)
+{
+    // at least 3 vertices, increasing order.
+    assert(ibegin1 + 3 <= iend1);
+    assert(ibegin1 >= 0 && iend1 <= its.vertices.size());
+    assert(ibegin2 + 3 <= iend2);
+    assert(ibegin2 >= 0 && iend2 <= its.vertices.size());
+    int n1 = iend1 - ibegin1;
+    int n2 = iend2 - ibegin2;
+    its.indices.reserve(its.indices.size() + (n1 + n2) * 3);
+
+    // For the first vertex of 1st strip, find the closest vertex on the 2nd strip.
+    int istart2 = ibegin2;
+    {
+        const Vec3f &p1    = its.vertices[ibegin1];
+        auto         d2min = std::numeric_limits<float>::max();
+        for (int i = ibegin2; i < iend2; ++ i) {
+            const Vec3f &p2 = its.vertices[i];
+            const float d2  = (p2 - p1).squaredNorm();
+            if (d2 < d2min) {
+                d2min = d2;
+                istart2 = i;
+            }
+        }
+    }
+
+    // Now triangulate the strip zig-zag fashion taking always the shortest connection if possible.
+    for (int u = ibegin1, v = istart2; n1 > 0 || n2 > 0;) {
+        bool take_first;
+        int u2, v2;
+        auto update_u2 = [&u2, u, ibegin1, iend1]() {
+            u2 = u;
+            if (++ u2 == iend1)
+                u2 = ibegin1;
+        };
+        auto update_v2 = [&v2, v, ibegin2, iend2]() {
+            v2 = v;
+            if (++ v2 == iend2)
+                v2 = ibegin2;
+        };
+        if (n1 == 0) {
+            take_first = false;
+            update_v2();
+        } else if (n2 == 0) {
+            take_first = true;
+            update_u2();
+        } else {
+            update_u2();
+            update_v2();
+            float l1 = (its.vertices[u2] - its.vertices[v]).squaredNorm();
+            float l2 = (its.vertices[v2] - its.vertices[u]).squaredNorm();
+            take_first = l1 < l2;
+        }
+        if (take_first) {
+            its.indices.push_back({ u, u2, v });
+            -- n1;
+            u = u2;
+        } else {
+            its.indices.push_back({ u, v2, v });
+            -- n2;
+            v = v2;
+        }
+    }
+}
+
+// Discretize 3D circle, append to output vector, return ranges of indices of the points added.
+static std::pair<int, int> discretize_circle(const Vec3f &center, const Vec3f &normal, const float radius, const float eps, std::vector<Vec3f> &pts)
+{
+    // Calculate discretization step and number of steps.
+    float angle_step = 2. * acos(1. - eps / radius);
+    auto  nsteps     = int(ceil(2 * M_PI / angle_step));
+    angle_step = 2 * M_PI / nsteps;
+
+    // Prepare coordinate system for the circle plane.
+    Vec3f x = normal.cross(Vec3f(0.f, -1.f, 0.f)).normalized();
+    Vec3f y = normal.cross(x).normalized();
+    assert(std::abs(x.cross(y).dot(normal) - 1.f) < EPSILON);
+
+    // Discretize the circle.
+    int begin = int(pts.size());
+    pts.reserve(pts.size() + nsteps);
+    float angle = 0;
+    x *= radius;
+    y *= radius;
+    for (int i = 0; i < nsteps; ++ i) {
+        pts.emplace_back(center + x * cos(angle) + y * sin(angle));
+        angle += angle_step;
+    }
+    return { begin, int(pts.size()) };
+}
+
+// Returns Z span of the generated mesh.
+static std::pair<float, float> extrude_branch(
+    const std::vector<const SupportElement*>    &path,
+    const TreeSupportSettings                   &config,
+    const SlicingParameters                     &slicing_params,
+    const std::vector<SupportElements>          &move_bounds,
+    indexed_triangle_set                        &result)
+{
+    Vec3d p1, p2, p3;
+    Vec3d v1, v2;
+    Vec3d nprev;
+    Vec3d ncurrent;
+    assert(path.size() >= 2);
+    static constexpr const float eps = 0.015f;
+    std::pair<int, int> prev_strip;
+
+//    char fname[2048];
+//    static int irun = 0;
+
+    float zmin, zmax;
+
+    for (size_t ipath = 1; ipath < path.size(); ++ ipath) {
+        const SupportElement &prev    = *path[ipath - 1];
+        const SupportElement &current = *path[ipath];
+        assert(prev.state.layer_idx + 1 == current.state.layer_idx);
+        p1 = to_3d(unscaled<double>(prev   .state.result_on_layer), layer_z(slicing_params, config, prev   .state.layer_idx));
+        p2 = to_3d(unscaled<double>(current.state.result_on_layer), layer_z(slicing_params, config, current.state.layer_idx));
+        v1 = (p2 - p1).normalized();
+        if (ipath == 1) {
+            nprev = v1;
+            // Extrude the bottom half sphere.
+            float radius     = unscaled<float>(getRadius(config, prev.state));
+            float angle_step = 2. * acos(1. - eps / radius);
+            auto  nsteps     = int(ceil(M_PI / (2. * angle_step)));
+            angle_step       = M_PI / (2. * nsteps);
+            int   ifan       = int(result.vertices.size());
+            result.vertices.emplace_back((p1 - nprev * radius).cast<float>());
+            zmin = result.vertices.back().z();
+            float angle = angle_step;
+            for (int i = 1; i < nsteps; ++ i, angle += angle_step) {
+                std::pair<int, int> strip = discretize_circle((p1 - nprev * radius * cos(angle)).cast<float>(), nprev.cast<float>(), radius * sin(angle), eps, result.vertices);
+                if (i == 1)
+                    triangulate_fan<false>(result, ifan, strip.first, strip.second);
+                else
+                    triangulate_strip(result, prev_strip.first, prev_strip.second, strip.first, strip.second);
+//                sprintf(fname, "d:\\temp\\meshes\\tree-partial-%d.obj", ++ irun);
+//                its_write_obj(result, fname);
+                prev_strip = strip;
+            }
+        }
+        if (ipath + 1 == path.size()) {
+            // End of the tube.
+            ncurrent = v1;
+            // Extrude the top half sphere.
+            float radius = unscaled<float>(getRadius(config, current.state));
+            float angle_step = 2. * acos(1. - eps / radius);
+            auto  nsteps = int(ceil(M_PI / (2. * angle_step)));
+            angle_step = M_PI / (2. * nsteps);
+            auto angle = float(M_PI / 2.);
+            for (int i = 0; i < nsteps; ++ i, angle -= angle_step) {
+                std::pair<int, int> strip = discretize_circle((p2 + ncurrent * radius * cos(angle)).cast<float>(), ncurrent.cast<float>(), radius * sin(angle), eps, result.vertices);
+                triangulate_strip(result, prev_strip.first, prev_strip.second, strip.first, strip.second);
+//                sprintf(fname, "d:\\temp\\meshes\\tree-partial-%d.obj", ++ irun);
+//                its_write_obj(result, fname);
+                prev_strip = strip;
+            }
+            int ifan = int(result.vertices.size());
+            result.vertices.emplace_back((p2 + ncurrent * radius).cast<float>());
+            zmax = result.vertices.back().z();
+            triangulate_fan<true>(result, ifan, prev_strip.first, prev_strip.second);
+//            sprintf(fname, "d:\\temp\\meshes\\tree-partial-%d.obj", ++ irun);
+//            its_write_obj(result, fname);
+        } else {
+            const SupportElement &next = *path[ipath + 1];
+            assert(current.state.layer_idx + 1 == next.state.layer_idx);
+            p3 = to_3d(unscaled<double>(next.state.result_on_layer), layer_z(slicing_params, config, next.state.layer_idx));
+            v2 = (p3 - p2).normalized();
+            ncurrent = (v1 + v2).normalized();
+            float radius = unscaled<float>(getRadius(config, current.state));
+            std::pair<int, int> strip = discretize_circle(p2.cast<float>(), ncurrent.cast<float>(), radius, eps, result.vertices);
+            triangulate_strip(result, prev_strip.first, prev_strip.second, strip.first, strip.second);
+            prev_strip = strip;
+//            sprintf(fname, "d:\\temp\\meshes\\tree-partial-%d.obj", ++irun);
+//            its_write_obj(result, fname);
+        }
+#if 0
+        if (circles_intersect(p1, nprev, settings.getRadius(prev), p2, ncurrent, settings.getRadius(current))) {
+            // Cannot connect previous and current slice using a simple zig-zag triangulation,
+            // because the two circles intersect.
+
+        } else {
+            // Continue with chaining.
+
+        }
+#endif
+    }
+
+    return std::make_pair(zmin, zmax);
+}
+
+#ifdef TREE_SUPPORT_ORGANIC_NUDGE_NEW
+
+// New version using per layer AABB trees of lines for nudging spheres away from an object.
+static void organic_smooth_branches_avoid_collisions(
+    const PrintObject                                   &print_object,
+    const TreeModelVolumes                              &volumes,
+    const TreeSupportSettings                           &config,
+    std::vector<SupportElements>                        &move_bounds,
+    const std::vector<std::pair<SupportElement*, int>>  &elements_with_link_down,
+    const std::vector<size_t>                           &linear_data_layers,
+    std::function<void()>                                throw_on_cancel)
+{
+    struct LayerCollisionCache {
+        coord_t          min_element_radius{ std::numeric_limits<coord_t>::max() };
+        bool             min_element_radius_known() const { return this->min_element_radius != std::numeric_limits<coord_t>::max(); }
+        coord_t          collision_radius{ 0 };
+        std::vector<Linef> lines;
+        AABBTreeIndirect::Tree<2, double> aabbtree_lines;
+        bool             empty() const { return this->lines.empty(); }
+    };
+    std::vector<LayerCollisionCache> layer_collision_cache;
+    layer_collision_cache.reserve(1024);
+    const SlicingParameters &slicing_params = print_object.slicing_parameters();
+    for (const std::pair<SupportElement*, int>& element : elements_with_link_down) {
+        LayerIndex layer_idx = element.first->state.layer_idx;
+        if (size_t num_layers = layer_idx + 1; num_layers > layer_collision_cache.size()) {
+            if (num_layers > layer_collision_cache.capacity())
+                reserve_power_of_2(layer_collision_cache, num_layers);
+            layer_collision_cache.resize(num_layers, {});
+        }
+        auto& l = layer_collision_cache[layer_idx];
+        l.min_element_radius = std::min(l.min_element_radius, getRadius(config, element.first->state));
+    }
+
+    throw_on_cancel();
+
+    for (LayerIndex layer_idx = 0; layer_idx < LayerIndex(layer_collision_cache.size()); ++layer_idx)
+        if (LayerCollisionCache& l = layer_collision_cache[layer_idx]; !l.min_element_radius_known())
+            l.min_element_radius = 0;
+        else {
+            //FIXME
+            l.min_element_radius = 0;
+            std::optional<std::pair<coord_t, std::reference_wrapper<const Polygons>>> res = volumes.get_collision_lower_bound_area(layer_idx, l.min_element_radius);
+            assert(res.has_value());
+            l.collision_radius = res->first;
+            Lines alines = to_lines(res->second.get());
+            l.lines.reserve(alines.size());
+            for (const Line &line : alines)
+                l.lines.push_back({ unscaled<double>(line.a), unscaled<double>(line.b) });
+            l.aabbtree_lines = AABBTreeLines::build_aabb_tree_over_indexed_lines(l.lines);
+            throw_on_cancel();
+        }
+
+    struct CollisionSphere {
+        const SupportElement& element;
+        int                   element_below_id;
+        const bool            locked;
+        float                 radius;
+        // Current position, when nudged away from the collision.
+        Vec3f                 position;
+        // Previous position, for Laplacian smoothing.
+        Vec3f                 prev_position;
+        // 
+        Vec3f                 last_collision;
+        double                last_collision_depth;
+        // Minimum Z for which the sphere collision will be evaluated.
+        // Limited by the minimum sloping angle and by the bottom of the tree.
+        float                 min_z{ -std::numeric_limits<float>::max() };
+        // Maximum Z for which the sphere collision will be evaluated.
+        // Limited by the minimum sloping angle and by the tip of the current branch.
+        float                 max_z{ std::numeric_limits<float>::max() };
+        uint32_t              layer_begin;
+        uint32_t              layer_end;
+    };
+
+    std::vector<CollisionSphere> collision_spheres;
+    collision_spheres.reserve(elements_with_link_down.size());
+    for (const std::pair<SupportElement*, int> &element_with_link : elements_with_link_down) {
+        const SupportElement &element   = *element_with_link.first;
+        const int             link_down = element_with_link.second;
+        collision_spheres.push_back({
+            element,
+            link_down,
+            // locked
+            element.parents.empty() || (link_down == -1 && element.state.layer_idx > 0),
+            unscaled<float>(getRadius(config, element.state)),
+            // 3D position
+            to_3d(unscaled<float>(element.state.result_on_layer), float(layer_z(slicing_params, config, element.state.layer_idx)))
+        });
+        // Update min_z coordinate to min_z of the tree below.
+        CollisionSphere &collision_sphere = collision_spheres.back();
+        if (link_down != -1) {
+            const size_t offset_below = linear_data_layers[element.state.layer_idx - 1];
+            collision_sphere.min_z = collision_spheres[offset_below + link_down].min_z;
+        } else
+            collision_sphere.min_z = collision_sphere.position.z();
+    }
+    // Update max_z by propagating max_z from the tips of the branches.
+    for (int collision_sphere_id = int(collision_spheres.size()) - 1; collision_sphere_id >= 0; -- collision_sphere_id) {
+        CollisionSphere &collision_sphere = collision_spheres[collision_sphere_id];
+        if (collision_sphere.element.parents.empty())
+            // Tip
+            collision_sphere.max_z = collision_sphere.position.z();
+        else {
+            // Below tip
+            const size_t offset_above = linear_data_layers[collision_sphere.element.state.layer_idx + 1];
+            for (auto iparent : collision_sphere.element.parents) {
+                float parent_z = collision_spheres[offset_above + iparent].max_z;
+//                    collision_sphere.max_z = collision_sphere.max_z == std::numeric_limits<float>::max() ? parent_z : std::max(collision_sphere.max_z, parent_z);
+                collision_sphere.max_z = std::min(collision_sphere.max_z, parent_z);
+            }
+        }
+    }
+    // Update min_z / max_z to limit the search Z span of a given sphere for collision detection.
+    for (CollisionSphere &collision_sphere : collision_spheres) {
+        //FIXME limit the collision span by the tree slope.
+        collision_sphere.min_z = std::max(collision_sphere.min_z, collision_sphere.position.z() - collision_sphere.radius);
+        collision_sphere.max_z = std::min(collision_sphere.max_z, collision_sphere.position.z() + collision_sphere.radius);
+        collision_sphere.layer_begin = std::min(collision_sphere.element.state.layer_idx, layer_idx_ceil(slicing_params, config, collision_sphere.min_z));
+        assert(collision_sphere.layer_begin < layer_collision_cache.size());
+        collision_sphere.layer_end   = std::min(LayerIndex(layer_collision_cache.size()), std::max(collision_sphere.element.state.layer_idx, layer_idx_floor(slicing_params, config, collision_sphere.max_z)) + 1);
+    }
+
+    throw_on_cancel();
+
+    static constexpr const double collision_extra_gap = 0.1;
+    static constexpr const double max_nudge_collision_avoidance = 0.5;
+    static constexpr const double max_nudge_smoothing = 0.2;
+    static constexpr const size_t num_iter = 100; // 1000;
+    for (size_t iter = 0; iter < num_iter; ++ iter) {
+        // Back up prev position before Laplacian smoothing.
+        for (CollisionSphere &collision_sphere : collision_spheres)
+            collision_sphere.prev_position = collision_sphere.position;
+        std::atomic<size_t> num_moved{ 0 };
+        tbb::parallel_for(tbb::blocked_range<size_t>(0, collision_spheres.size()),
+            [&collision_spheres, &layer_collision_cache, &slicing_params, &config, &move_bounds, &linear_data_layers, &num_moved, &throw_on_cancel](const tbb::blocked_range<size_t> range) {
+            for (size_t collision_sphere_id = range.begin(); collision_sphere_id < range.end(); ++ collision_sphere_id)
+                if (CollisionSphere &collision_sphere = collision_spheres[collision_sphere_id]; ! collision_sphere.locked) {
+                    // Calculate collision of multiple 2D layers against a collision sphere.
+                    collision_sphere.last_collision_depth = - std::numeric_limits<double>::max();
+                    for (uint32_t layer_id = collision_sphere.layer_begin; layer_id != collision_sphere.layer_end; ++ layer_id) {
+                        double dz = (layer_id - collision_sphere.element.state.layer_idx) * slicing_params.layer_height;
+                        if (double r2 = sqr(collision_sphere.radius) - sqr(dz); r2 > 0) {
+                            if (const LayerCollisionCache &layer_collision_cache_item = layer_collision_cache[layer_id]; ! layer_collision_cache_item.empty()) {
+                                size_t hit_idx_out;
+                                Vec2d  hit_point_out;
+                                if (double dist = sqrt(AABBTreeLines::squared_distance_to_indexed_lines(
+                                    layer_collision_cache_item.lines, layer_collision_cache_item.aabbtree_lines, Vec2d(to_2d(collision_sphere.position).cast<double>()),
+                                    hit_idx_out, hit_point_out, r2)); dist >= 0.) {
+                                    double collision_depth = sqrt(r2) - dist;
+                                    if (collision_depth > collision_sphere.last_collision_depth) {
+                                        collision_sphere.last_collision_depth = collision_depth;
+                                        collision_sphere.last_collision = to_3d(hit_point_out.cast<float>(), float(layer_z(slicing_params, config, layer_id)));
+                                    }
+                                }
+                            }
+                        }
+                    }
+                    if (collision_sphere.last_collision_depth > 0) {
+                        // Collision detected to be removed.
+                        // Nudge the circle center away from the collision.
+                        if (collision_sphere.last_collision_depth > EPSILON)
+                            // a little bit of hysteresis to detect end of 
+                            ++ num_moved;
+                        // Shift by maximum 2mm.
+                        double nudge_dist = std::min(std::max(0., collision_sphere.last_collision_depth + collision_extra_gap), max_nudge_collision_avoidance);
+                        Vec2d nudge_vector = (to_2d(collision_sphere.position) - to_2d(collision_sphere.last_collision)).cast<double>().normalized() * nudge_dist;
+                        collision_sphere.position.head<2>() += (nudge_vector * nudge_dist).cast<float>();
+                    }
+                    // Laplacian smoothing
+                    Vec2d avg{ 0, 0 };
+                    const SupportElements &above = move_bounds[collision_sphere.element.state.layer_idx + 1];
+                    const size_t           offset_above = linear_data_layers[collision_sphere.element.state.layer_idx + 1];
+                    double weight = 0.;
+                    for (auto iparent : collision_sphere.element.parents) {
+                        double w = collision_sphere.radius;
+                        avg += w * to_2d(collision_spheres[offset_above + iparent].prev_position.cast<double>());
+                        weight += w;
+                    }
+                    if (collision_sphere.element_below_id != -1) {
+                        const size_t offset_below = linear_data_layers[collision_sphere.element.state.layer_idx - 1];
+                        const double w = weight; //  config.getRadius(move_bounds[element.state.layer_idx - 1][below].state);
+                        avg += w * to_2d(collision_spheres[offset_below + collision_sphere.element_below_id].prev_position.cast<double>());
+                        weight += w;
+                    }
+                    avg /= weight;
+                    static constexpr const double smoothing_factor = 0.5;
+                    Vec2d old_pos = to_2d(collision_sphere.position).cast<double>();
+                    Vec2d new_pos = (1. - smoothing_factor) * old_pos + smoothing_factor * avg;
+                    Vec2d shift   = new_pos - old_pos;
+                    double nudge_dist_max = shift.norm();
+                    // Shift by maximum 1mm, less than the collision avoidance factor.
+                    double nudge_dist = std::min(std::max(0., nudge_dist_max), max_nudge_smoothing);
+                    collision_sphere.position.head<2>() += (shift.normalized() * nudge_dist).cast<float>();
+
+                    throw_on_cancel();
+                }
+        });
+#if 0
+        std::vector<double> stat;
+        for (CollisionSphere& collision_sphere : collision_spheres)
+            if (!collision_sphere.locked)
+                stat.emplace_back(collision_sphere.last_collision_depth);
+        std::sort(stat.begin(), stat.end());
+        printf("iteration: %d, moved: %d, collision depth: min %lf, max %lf, median %lf\n", int(iter), int(num_moved), stat.front(), stat.back(), stat[stat.size() / 2]);
+#endif
+        if (num_moved == 0)
+            break;
+    }
+
+    for (size_t i = 0; i < collision_spheres.size(); ++ i)
+        elements_with_link_down[i].first->state.result_on_layer = scaled<coord_t>(to_2d(collision_spheres[i].position));
+}
+#else // TREE_SUPPORT_ORGANIC_NUDGE_NEW
+// Old version using OpenVDB, works but it is extremely slow for complex meshes.
+static void organic_smooth_branches_avoid_collisions(
+    const PrintObject                                   &print_object,
+    const TreeModelVolumes                              &volumes,
+    const TreeSupportSettings                           &config,
+    std::vector<SupportElements>                        &move_bounds,
+    const std::vector<std::pair<SupportElement*, int>>  &elements_with_link_down,
+    const std::vector<size_t>                           &linear_data_layers,
+    std::function<void()>                                throw_on_cancel)
+{
+    TriangleMesh mesh = print_object.model_object()->raw_mesh();
+    mesh.transform(print_object.trafo_centered());
+    double scale = 10.;
+    openvdb::FloatGrid::Ptr grid = mesh_to_grid(mesh.its, openvdb::math::Transform{}, scale, 0., 0.);
+    std::unique_ptr<openvdb::tools::ClosestSurfacePoint<openvdb::FloatGrid>> closest_surface_point = openvdb::tools::ClosestSurfacePoint<openvdb::FloatGrid>::create(*grid);
+    std::vector<openvdb::Vec3R> pts, prev, projections;
+    std::vector<float> distances;
+    for (const std::pair<SupportElement*, int>& element : elements_with_link_down) {
+        Vec3d pt = to_3d(unscaled<double>(element.first->state.result_on_layer), layer_z(print_object.slicing_parameters(), config, element.first->state.layer_idx)) * scale;
+        pts.push_back({ pt.x(), pt.y(), pt.z() });
+    }
+
+    const double collision_extra_gap = 1. * scale;
+    const double max_nudge_collision_avoidance = 2. * scale;
+    const double max_nudge_smoothing = 1. * scale;
+
+    static constexpr const size_t num_iter = 100; // 1000;
+    for (size_t iter = 0; iter < num_iter; ++ iter) {
+        prev = pts;
+        projections = pts;
+        distances.assign(pts.size(), std::numeric_limits<float>::max());
+        closest_surface_point->searchAndReplace(projections, distances);
+        size_t num_moved = 0;
+        for (size_t i = 0; i < projections.size(); ++ i) {
+            const SupportElement &element = *elements_with_link_down[i].first;
+            const int            below    = elements_with_link_down[i].second;
+            const bool           locked   = (below == -1 && element.state.layer_idx > 0) || element.state.locked();
+            if (! locked && pts[i] != projections[i]) {
+                // Nudge the circle center away from the collision.
+                Vec3d v{ projections[i].x() - pts[i].x(), projections[i].y() - pts[i].y(), projections[i].z() - pts[i].z() };
+                double depth = v.norm();
+                assert(std::abs(distances[i] - depth) < EPSILON);
+                double radius = unscaled<double>(config.getRadius(element.state)) * scale;
+                if (depth < radius) {
+                    // Collision detected to be removed.
+                    ++ num_moved;
+                    double dxy = sqrt(sqr(radius) - sqr(v.z()));
+                    double nudge_dist_max = dxy - std::hypot(v.x(), v.y())
+                        //FIXME 1mm gap
+                        + collision_extra_gap;
+                    // Shift by maximum 2mm.
+                    double nudge_dist = std::min(std::max(0., nudge_dist_max), max_nudge_collision_avoidance);
+                    Vec2d nudge_v = to_2d(v).normalized() * (- nudge_dist);
+                    pts[i].x() += nudge_v.x();
+                    pts[i].y() += nudge_v.y();
+                }
+            }
+            // Laplacian smoothing
+            if (! locked && ! element.parents.empty()) {
+                Vec2d avg{ 0, 0 };
+                const SupportElements &above = move_bounds[element.state.layer_idx + 1];
+                const size_t           offset_above = linear_data_layers[element.state.layer_idx + 1];
+                double weight = 0.;
+                for (auto iparent : element.parents) {
+                    double w = config.getRadius(above[iparent].state);
+                    avg.x() += w * prev[offset_above + iparent].x();
+                    avg.y() += w * prev[offset_above + iparent].y();
+                    weight += w;
+                }
+                size_t cnt = element.parents.size();
+                if (below != -1) {
+                    const size_t offset_below = linear_data_layers[element.state.layer_idx - 1];
+                    const double w = weight; //  config.getRadius(move_bounds[element.state.layer_idx - 1][below].state);
+                    avg.x() += w * prev[offset_below + below].x();
+                    avg.y() += w * prev[offset_below + below].y();
+                    ++ cnt;
+                    weight += w;
+                }
+                //avg /= double(cnt);
+                avg /= weight;
+                static constexpr const double smoothing_factor = 0.5;
+                Vec2d old_pos{ pts[i].x(), pts[i].y() };
+                Vec2d new_pos = (1. - smoothing_factor) * old_pos + smoothing_factor * avg;
+                Vec2d shift = new_pos - old_pos;
+                double nudge_dist_max = shift.norm();
+                // Shift by maximum 1mm, less than the collision avoidance factor.
+                double nudge_dist = std::min(std::max(0., nudge_dist_max), max_nudge_smoothing);
+                Vec2d nudge_v = shift.normalized() * nudge_dist;
+                pts[i].x() += nudge_v.x();
+                pts[i].y() += nudge_v.y();
+            }
+        }
+//            printf("iteration: %d, moved: %d\n", int(iter), int(num_moved));
+        if (num_moved == 0)
+            break;
+    }
+
+    for (size_t i = 0; i < projections.size(); ++ i) {
+        elements_with_link_down[i].first->state.result_on_layer.x() = scaled<coord_t>(pts[i].x()) / scale;
+        elements_with_link_down[i].first->state.result_on_layer.y() = scaled<coord_t>(pts[i].y()) / scale;
+    }
+}
+#endif // TREE_SUPPORT_ORGANIC_NUDGE_NEW
+
+// Organic specific: Smooth branches and produce one cummulative mesh to be sliced.
+void organic_draw_branches(
+    PrintObject                     &print_object,
+    TreeModelVolumes                &volumes, 
+    const TreeSupportSettings       &config,
+    std::vector<SupportElements>    &move_bounds,
+
+    // I/O:
+    SupportGeneratorLayersPtr       &bottom_contacts,
+    SupportGeneratorLayersPtr       &top_contacts,
+    InterfacePlacer                 &interface_placer,
+
+    // Output:
+    SupportGeneratorLayersPtr       &intermediate_layers,
+    SupportGeneratorLayerStorage    &layer_storage,
+
+    std::function<void()>            throw_on_cancel)
+{
+    // All SupportElements are put into a layer independent storage to improve parallelization.
+    std::vector<std::pair<SupportElement*, int>> elements_with_link_down;
+    std::vector<size_t>                          linear_data_layers;
+    {
+        std::vector<std::pair<SupportElement*, int>> map_downwards_old;
+        std::vector<std::pair<SupportElement*, int>> map_downwards_new;
+        linear_data_layers.emplace_back(0);
+        for (LayerIndex layer_idx = 0; layer_idx < LayerIndex(move_bounds.size()); ++ layer_idx) {
+            SupportElements *layer_above = layer_idx + 1 < move_bounds.size() ? &move_bounds[layer_idx + 1] : nullptr;
+            map_downwards_new.clear();
+            std::sort(map_downwards_old.begin(), map_downwards_old.end(), [](auto& l, auto& r) { return l.first < r.first;  });
+            SupportElements &layer = move_bounds[layer_idx];
+            for (size_t elem_idx = 0; elem_idx < layer.size(); ++ elem_idx) {
+                SupportElement &elem = layer[elem_idx];
+                int child = -1;
+                if (layer_idx > 0) {
+                    auto it = std::lower_bound(map_downwards_old.begin(), map_downwards_old.end(), &elem, [](auto& l, const SupportElement* r) { return l.first < r; });
+                    if (it != map_downwards_old.end() && it->first == &elem) {
+                        child = it->second;
+                        // Only one link points to a node above from below.
+                        assert(!(++it != map_downwards_old.end() && it->first == &elem));
+                    }
+#ifndef NDEBUG
+                    {
+                        const SupportElement *pchild = child == -1 ? nullptr : &move_bounds[layer_idx - 1][child];
+                        assert(pchild ? pchild->state.result_on_layer_is_set() : elem.state.target_height > layer_idx);
+                    }
+#endif // NDEBUG
+                }
+                for (int32_t parent_idx : elem.parents) {
+                    SupportElement &parent = (*layer_above)[parent_idx];
+                    if (parent.state.result_on_layer_is_set())
+                        map_downwards_new.emplace_back(&parent, elem_idx);
+                }
+
+                elements_with_link_down.push_back({ &elem, int(child) });
+            }
+            std::swap(map_downwards_old, map_downwards_new);
+            linear_data_layers.emplace_back(elements_with_link_down.size());
+        }
+    }
+
+    throw_on_cancel();
+
+    organic_smooth_branches_avoid_collisions(print_object, volumes, config, move_bounds, elements_with_link_down, linear_data_layers, throw_on_cancel);
+
+    // Reduce memory footprint. After this point only finalize_interface_and_support_areas() will use volumes and from that only collisions with zero radius will be used.
+    volumes.clear_all_but_object_collision();
+
+    // Unmark all nodes.
+    for (SupportElements &elements : move_bounds)
+        for (SupportElement &element : elements)
+            element.state.marked = false;
+
+    // Traverse all nodes, generate tubes.
+    // Traversal stack with nodes and their current parent
+
+    struct Branch {
+        std::vector<const SupportElement*> path;
+        bool                               has_root{ false };
+        bool                               has_tip { false };
+    };
+
+    struct Slice {
+        Polygons polygons;
+        Polygons bottom_contacts;
+        size_t   num_branches{ 0 };
+    };
+
+    struct Tree {
+        std::vector<Branch>  branches;
+
+        std::vector<Slice>   slices;
+        LayerIndex           first_layer_id{ -1 };
+    };
+
+    std::vector<Tree>        trees;
+
+    struct TreeVisitor {
+        static void visit_recursive(std::vector<SupportElements> &move_bounds, SupportElement &start_element, Tree &out) {
+            assert(! start_element.state.marked && ! start_element.parents.empty());
+            // Collect elements up to a bifurcation above.
+            start_element.state.marked = true;
+            // For each branch bifurcating from this point:
+            SupportElements &layer       = move_bounds[start_element.state.layer_idx];
+            SupportElements &layer_above = move_bounds[start_element.state.layer_idx + 1];
+            bool root = out.branches.empty();
+            for (size_t parent_idx = 0; parent_idx < start_element.parents.size(); ++ parent_idx) {
+                Branch branch;
+                branch.path.emplace_back(&start_element);
+                // Traverse each branch until it branches again.
+                SupportElement &first_parent = layer_above[start_element.parents[parent_idx]];
+                assert(! first_parent.state.marked);
+                assert(branch.path.back()->state.layer_idx + 1 == first_parent.state.layer_idx);
+                branch.path.emplace_back(&first_parent);
+                if (first_parent.parents.size() < 2)
+                    first_parent.state.marked = true;
+                SupportElement *next_branch = nullptr;
+                if (first_parent.parents.size() == 1) {
+                    for (SupportElement *parent = &first_parent;;) {
+                        assert(parent->state.marked);
+                        SupportElement &next_parent = move_bounds[parent->state.layer_idx + 1][parent->parents.front()];
+                        assert(! next_parent.state.marked);
+                        assert(branch.path.back()->state.layer_idx + 1 == next_parent.state.layer_idx);
+                        branch.path.emplace_back(&next_parent);
+                        if (next_parent.parents.size() > 1) {
+                            // Branching point was reached.
+                            next_branch = &next_parent;
+                            break;
+                        }
+                        next_parent.state.marked = true;
+                        if (next_parent.parents.size() == 0)
+                            // Tip is reached.
+                            break;
+                        parent = &next_parent;
+                    }
+                } else if (first_parent.parents.size() > 1)
+                    // Branching point was reached.
+                    next_branch = &first_parent;
+                assert(branch.path.size() >= 2);
+                assert(next_branch == nullptr || ! next_branch->state.marked);
+                branch.has_root = root;
+                branch.has_tip  = ! next_branch;
+                out.branches.emplace_back(std::move(branch));
+                if (next_branch)
+                    visit_recursive(move_bounds, *next_branch, out);
+            }
+        }
+    };
+
+    for (LayerIndex layer_idx = 0; layer_idx + 1 < LayerIndex(move_bounds.size()); ++ layer_idx) {
+//        int ielement;
+        for (SupportElement& start_element : move_bounds[layer_idx]) {
+            if (!start_element.state.marked && !start_element.parents.empty()) {
+#if 0
+                int found = 0;
+                if (layer_idx > 0) {
+                    for (auto& el : move_bounds[layer_idx - 1]) {
+                        for (auto iparent : el.parents)
+                            if (iparent == ielement)
+                                ++found;
+                    }
+                    if (found != 0)
+                        printf("Found: %d\n", found);
+                }
+#endif
+                trees.push_back({});
+                TreeVisitor::visit_recursive(move_bounds, start_element, trees.back());
+                assert(!trees.back().branches.empty());
+                //FIXME debugging
+#if 1
+                if (start_element.state.lost) {
+                }
+                else if (start_element.state.verylost) {
+                } else
+                    trees.pop_back();
+#endif
+            }
+//            ++ ielement;
+        }
+    }
+
+    const SlicingParameters &slicing_params = print_object.slicing_parameters();
+    MeshSlicingParams mesh_slicing_params;
+    mesh_slicing_params.mode = MeshSlicingParams::SlicingMode::Positive;
+
+    tbb::parallel_for(tbb::blocked_range<size_t>(0, trees.size(), 1),
+        [&trees, &volumes, &config, &slicing_params, &move_bounds, &interface_placer, &mesh_slicing_params, &throw_on_cancel](const tbb::blocked_range<size_t> &range) {
+            indexed_triangle_set    partial_mesh;
+            std::vector<float>      slice_z;
+            std::vector<Polygons>   bottom_contacts;
+            for (size_t tree_id = range.begin(); tree_id < range.end(); ++ tree_id) {
+                Tree &tree = trees[tree_id];
+                for (const Branch &branch : tree.branches) {
+                    // Triangulate the tube.
+                    partial_mesh.clear();
+                    std::pair<float, float> zspan = extrude_branch(branch.path, config, slicing_params, move_bounds, partial_mesh);
+                    LayerIndex layer_begin = branch.has_root ?
+                        branch.path.front()->state.layer_idx : 
+                        std::min(branch.path.front()->state.layer_idx, layer_idx_ceil(slicing_params, config, zspan.first));
+                    LayerIndex layer_end   = (branch.has_tip ?
+                        branch.path.back()->state.layer_idx :
+                        std::max(branch.path.back()->state.layer_idx, layer_idx_floor(slicing_params, config, zspan.second))) + 1;
+                    slice_z.clear();
+                    for (LayerIndex layer_idx = layer_begin; layer_idx < layer_end; ++ layer_idx) {
+                        const double print_z  = layer_z(slicing_params, config, layer_idx);
+                        const double bottom_z = layer_idx > 0 ? layer_z(slicing_params, config, layer_idx - 1) : 0.;
+                        slice_z.emplace_back(float(0.5 * (bottom_z + print_z)));
+                    }
+                    std::vector<Polygons> slices = slice_mesh(partial_mesh, slice_z, mesh_slicing_params, throw_on_cancel);
+                    bottom_contacts.clear();
+                    //FIXME parallelize?
+                    for (LayerIndex i = 0; i < LayerIndex(slices.size()); ++ i)
+                        slices[i] = diff_clipped(slices[i], volumes.getCollision(0, layer_begin + i, true)); //FIXME parent_uses_min || draw_area.element->state.use_min_xy_dist);
+
+                    size_t num_empty = 0;
+                    if (slices.front().empty()) {
+                        // Some of the initial layers are empty.
+                        num_empty = std::find_if(slices.begin(), slices.end(), [](auto &s) { return !s.empty(); }) - slices.begin();
+                    } else {
+                        if (branch.has_root) {
+                            if (branch.path.front()->state.to_model_gracious) {
+                                if (config.settings.support_floor_layers > 0)
+                                    //FIXME one may just take the whole tree slice as bottom interface.
+                                    bottom_contacts.emplace_back(intersection_clipped(slices.front(), volumes.getPlaceableAreas(0, layer_begin, [] {})));
+                            } else if (layer_begin > 0) {
+                                // Drop down areas that do rest non - gracefully on the model to ensure the branch actually rests on something.
+                                struct BottomExtraSlice {
+                                    Polygons polygons;
+                                    double   area;
+                                };
+                                std::vector<BottomExtraSlice>   bottom_extra_slices;
+                                Polygons                        rest_support;
+                                coord_t                         bottom_radius = getRadius(config, branch.path.front()->state);
+                                // Don't propagate further than 1.5 * bottom radius.
+                                //LayerIndex                      layers_propagate_max = 2 * bottom_radius / config.layer_height;
+                                LayerIndex                      layers_propagate_max = 5 * bottom_radius / config.layer_height;
+                                LayerIndex                      layer_bottommost = branch.path.front()->state.verylost ? 
+                                    // If the tree bottom is hanging in the air, bring it down to some surface.
+                                    0 : 
+                                    //FIXME the "verylost" branches should stop when crossing another support.
+                                    std::max(0, layer_begin - layers_propagate_max);
+                                double                          support_area_min_radius = M_PI * sqr(double(config.branch_radius));
+                                double                          support_area_stop = std::max(0.2 * M_PI * sqr(double(bottom_radius)), 0.5 * support_area_min_radius);
+                                 // Only propagate until the rest area is smaller than this threshold.
+                                double                          support_area_min = 0.1 * support_area_min_radius;
+                                for (LayerIndex layer_idx = layer_begin - 1; layer_idx >= layer_bottommost; -- layer_idx) {
+                                    rest_support = diff_clipped(rest_support.empty() ? slices.front() : rest_support, volumes.getCollision(0, layer_idx, false));
+                                    double rest_support_area = area(rest_support);
+                                    if (rest_support_area < support_area_stop)
+                                        // Don't propagate a fraction of the tree contact surface.
+                                        break;
+                                    bottom_extra_slices.push_back({ rest_support, rest_support_area });
+                                }
+                                // Now remove those bottom slices that are not supported at all.
+#if 0
+                                while (! bottom_extra_slices.empty()) {
+                                    Polygons this_bottom_contacts = intersection_clipped(
+                                        bottom_extra_slices.back().polygons, volumes.getPlaceableAreas(0, layer_begin - LayerIndex(bottom_extra_slices.size()), [] {}));
+                                    if (area(this_bottom_contacts) < support_area_min)
+                                        bottom_extra_slices.pop_back();
+                                    else {
+                                        // At least a fraction of the tree bottom is considered to be supported.
+                                        if (config.settings.support_floor_layers > 0)
+                                            // Turn this fraction of the tree bottom into a contact layer.
+                                            bottom_contacts.emplace_back(std::move(this_bottom_contacts));
+                                        break;
+                                    }
+                                }
+#endif
+                                if (config.settings.support_floor_layers > 0)
+                                    for (int i = int(bottom_extra_slices.size()) - 2; i >= 0; -- i)
+                                        bottom_contacts.emplace_back(
+                                            intersection_clipped(bottom_extra_slices[i].polygons, volumes.getPlaceableAreas(0, layer_begin - i - 1, [] {})));
+                                layer_begin -= LayerIndex(bottom_extra_slices.size());
+                                slices.insert(slices.begin(), bottom_extra_slices.size(), {});
+                                auto it_dst = slices.begin();
+                                for (auto it_src = bottom_extra_slices.rbegin(); it_src != bottom_extra_slices.rend(); ++ it_src)
+                                    *it_dst ++ = std::move(it_src->polygons);
+                            }
+                        }
+                        
+#if 0
+                        //FIXME branch.has_tip seems to not be reliable.
+                        if (branch.has_tip && interface_placer.support_parameters.has_top_contacts)
+                            // Add top slices to top contacts / interfaces / base interfaces.
+                            for (int i = int(branch.path.size()) - 1; i >= 0; -- i) {
+                                const SupportElement &el = *branch.path[i];
+                                if (el.state.missing_roof_layers == 0)
+                                    break;
+                                //FIXME Move or not?
+                                interface_placer.add_roof(std::move(slices[int(slices.size()) - i - 1]), el.state.layer_idx,
+                                    interface_placer.support_parameters.num_top_interface_layers + 1 - el.state.missing_roof_layers);
+                            }
+#endif
+                    }
+
+                    layer_begin += LayerIndex(num_empty);
+                    while (! slices.empty() && slices.back().empty()) {
+                        slices.pop_back();
+                        -- layer_end;
+                    }
+                    if (layer_begin < layer_end) {
+                        LayerIndex new_begin = tree.first_layer_id == -1 ? layer_begin : std::min(tree.first_layer_id, layer_begin);
+                        LayerIndex new_end   = tree.first_layer_id == -1 ? layer_end : std::max(tree.first_layer_id + LayerIndex(tree.slices.size()), layer_end);
+                        size_t     new_size  = size_t(new_end - new_begin);
+                        if (tree.first_layer_id == -1) {
+                        } else if (tree.slices.capacity() < new_size) {
+                            std::vector<Slice> new_slices;
+                            new_slices.reserve(new_size);
+                            if (LayerIndex dif = tree.first_layer_id - new_begin; dif > 0)
+                                new_slices.insert(new_slices.end(), dif, {});
+                            append(new_slices, std::move(tree.slices));
+                            tree.slices.swap(new_slices);
+                        } else if (LayerIndex dif = tree.first_layer_id - new_begin; dif > 0)
+                            tree.slices.insert(tree.slices.begin(), tree.first_layer_id - new_begin, {});
+                        tree.slices.insert(tree.slices.end(), new_size - tree.slices.size(), {});
+                        layer_begin -= LayerIndex(num_empty);
+                        for (LayerIndex i = layer_begin; i != layer_end; ++ i) {
+                            int j = i - layer_begin;
+                            if (Polygons &src = slices[j]; ! src.empty()) {
+                                Slice &dst = tree.slices[i - new_begin];
+                                if (++ dst.num_branches > 1) {
+                                    append(dst.polygons, std::move(src));
+                                    if (j < bottom_contacts.size())
+                                        append(dst.bottom_contacts, std::move(bottom_contacts[j]));
+                                } else {
+                                    dst.polygons = std::move(std::move(src));
+                                    if (j < bottom_contacts.size())
+                                        dst.bottom_contacts = std::move(bottom_contacts[j]);
+                                }
+                            }
+                        }
+                        tree.first_layer_id = new_begin;
+                    }
+                }
+            }
+        }, tbb::simple_partitioner());
+
+    tbb::parallel_for(tbb::blocked_range<size_t>(0, trees.size(), 1),
+        [&trees, &throw_on_cancel](const tbb::blocked_range<size_t> &range) {
+        for (size_t tree_id = range.begin(); tree_id < range.end(); ++ tree_id) {
+            Tree &tree = trees[tree_id];
+            for (Slice &slice : tree.slices)
+                if (slice.num_branches > 1) {
+                    slice.polygons        = union_(slice.polygons);
+                    slice.bottom_contacts = union_(slice.bottom_contacts);
+                    slice.num_branches = 1;
+                }
+            throw_on_cancel();
+        }
+    }, tbb::simple_partitioner());
+
+    size_t num_layers = 0;
+    for (Tree &tree : trees)
+        if (tree.first_layer_id >= 0)
+            num_layers = std::max(num_layers, size_t(tree.first_layer_id + tree.slices.size()));
+
+    std::vector<Slice> slices(num_layers, Slice{});
+    for (Tree &tree : trees)
+        if (tree.first_layer_id >= 0) {
+            for (LayerIndex i = tree.first_layer_id; i != tree.first_layer_id + LayerIndex(tree.slices.size()); ++ i)
+                if (Slice &src = tree.slices[i - tree.first_layer_id]; ! src.polygons.empty()) {
+                    Slice &dst = slices[i];
+                    if (++ dst.num_branches > 1) {
+                        append(dst.polygons,        std::move(src.polygons));
+                        append(dst.bottom_contacts, std::move(src.bottom_contacts));
+                    } else {
+                        dst.polygons        = std::move(src.polygons);
+                        dst.bottom_contacts = std::move(src.bottom_contacts);
+                    }
+                }
+        }
+
+    tbb::parallel_for(tbb::blocked_range<size_t>(0, std::min(move_bounds.size(), slices.size()), 1),
+        [&print_object, &config, &slices, &bottom_contacts, &top_contacts, &intermediate_layers, &layer_storage, &throw_on_cancel](const tbb::blocked_range<size_t> &range) {
+        for (size_t layer_idx = range.begin(); layer_idx < range.end(); ++layer_idx) {
+            Slice &slice = slices[layer_idx];
+            assert(intermediate_layers[layer_idx] == nullptr);
+            Polygons base_layer_polygons     = slice.num_branches > 1 ? union_(slice.polygons) : std::move(slice.polygons);
+            Polygons bottom_contact_polygons = slice.num_branches > 1 ? union_(slice.bottom_contacts) : std::move(slice.bottom_contacts);
+
+            if (! base_layer_polygons.empty()) {
+                // Most of the time in this function is this union call. Can take 300+ ms when a lot of areas are to be unioned.
+                base_layer_polygons = smooth_outward(union_(base_layer_polygons), config.support_line_width); //FIXME was .smooth(50);
+                //smooth_outward(closing(std::move(bottom), closing_distance + minimum_island_radius, closing_distance, SUPPORT_SURFACES_OFFSET_PARAMETERS), smoothing_distance) :
+                // simplify a bit, to ensure the output does not contain outrageous amounts of vertices. Should not be necessary, just a precaution.
+                base_layer_polygons = polygons_simplify(base_layer_polygons, std::min(scaled<double>(0.03), double(config.resolution)), polygons_strictly_simple);
+            }
+
+            // Subtract top contact layer polygons from support base.
+            SupportGeneratorLayer *top_contact_layer = top_contacts.empty() ? nullptr : top_contacts[layer_idx];
+            if (top_contact_layer && ! top_contact_layer->polygons.empty() && ! base_layer_polygons.empty()) {
+                base_layer_polygons = diff(base_layer_polygons, top_contact_layer->polygons);
+                if (! bottom_contact_polygons.empty())
+                    //FIXME it may be better to clip bottom contacts with top contacts first after they are propagated to produce interface layers.
+                    bottom_contact_polygons = diff(bottom_contact_polygons, top_contact_layer->polygons);
+            }
+            if (! bottom_contact_polygons.empty()) {
+                base_layer_polygons = diff(base_layer_polygons, bottom_contact_polygons);
+                SupportGeneratorLayer *bottom_contact_layer = bottom_contacts[layer_idx] = &layer_allocate(
+                    layer_storage, SupporLayerType::BottomContact, print_object.slicing_parameters(), config, layer_idx);
+                bottom_contact_layer->polygons = std::move(bottom_contact_polygons);
+            }
+            if (! base_layer_polygons.empty()) {
+                SupportGeneratorLayer *base_layer = intermediate_layers[layer_idx] = &layer_allocate(
+                    layer_storage, SupporLayerType::Base, print_object.slicing_parameters(), config, layer_idx);
+                base_layer->polygons = union_(base_layer_polygons);
+            }
+
+            throw_on_cancel();
+        }
+    }, tbb::simple_partitioner());
+}
+
+} // namespace FFFTreeSupport
+
+} // namespace Slic3r

src/libslic3r/Support/OrganicSupport.hpp

@@ -0,0 +1,39 @@
+#ifndef slic3r_OrganicSupport_hpp
+#define slic3r_OrganicSupport_hpp
+
+#include "SupportCommon.hpp"
+#include "TreeSupport.hpp"
+
+namespace Slic3r
+{
+
+class PrintObject;
+
+namespace FFFTreeSupport
+{
+
+class TreeModelVolumes;
+
+// Organic specific: Smooth branches and produce one cummulative mesh to be sliced.
+void organic_draw_branches(
+    PrintObject                     &print_object,
+    TreeModelVolumes                &volumes, 
+    const TreeSupportSettings       &config,
+    std::vector<SupportElements>    &move_bounds,
+
+    // I/O:
+    SupportGeneratorLayersPtr       &bottom_contacts,
+    SupportGeneratorLayersPtr       &top_contacts,
+    InterfacePlacer                 &interface_placer,
+
+    // Output:
+    SupportGeneratorLayersPtr       &intermediate_layers,
+    SupportGeneratorLayerStorage    &layer_storage,
+
+    std::function<void()>            throw_on_cancel);
+
+} // namespace FFFTreeSupport
+
+} // namespace Slic3r
+
+#endif // slic3r_OrganicSupport_hpp

src/libslic3r/Support/SupportCommon.hpp

@@ -1,7 +1,9 @@
 #ifndef slic3r_SupportCommon_hpp_
 #define slic3r_SupportCommon_hpp_
 
+#include "../Layer.hpp"
 #include "../Polygon.hpp"
+#include "../Print.hpp"
 #include "SupportLayer.hpp"
 #include "SupportParameters.hpp"
 

src/libslic3r/Support/TreeModelVolumes.cpp

@@ -35,75 +35,6 @@ using namespace std::literals;
 // had to use a define beacuse the macro processing inside macro BOOST_LOG_TRIVIAL()
 #define error_level_not_in_cache error
 
-static constexpr const bool polygons_strictly_simple = false;
-
-TreeSupportMeshGroupSettings::TreeSupportMeshGroupSettings(const PrintObject &print_object)
-{
-    const PrintConfig       &print_config       = print_object.print()->config();
-    const PrintObjectConfig &config             = print_object.config();
-    const SlicingParameters &slicing_params     = print_object.slicing_parameters();
-//    const std::vector<unsigned int>  printing_extruders = print_object.object_extruders();
-
-    // Support must be enabled and set to Tree style.
-    assert(config.support_material || config.support_material_enforce_layers > 0);
-    assert(config.support_material_style == smsTree || config.support_material_style == smsOrganic);
-
-    // Calculate maximum external perimeter width over all printing regions, taking into account the default layer height.
-    coordf_t external_perimeter_width = 0.;
-    for (size_t region_id = 0; region_id < print_object.num_printing_regions(); ++ region_id) {
-        const PrintRegion &region = print_object.printing_region(region_id);
-        external_perimeter_width = std::max<coordf_t>(external_perimeter_width, region.flow(print_object, frExternalPerimeter, config.layer_height).width());
-    }
-
-    this->layer_height              = scaled<coord_t>(config.layer_height.value);
-    this->resolution                = scaled<coord_t>(print_config.gcode_resolution.value);
-    // Arache feature
-    this->min_feature_size          = scaled<coord_t>(config.min_feature_size.value);
-    // +1 makes the threshold inclusive
-    this->support_angle             = 0.5 * M_PI - std::clamp<double>((config.support_material_threshold + 1) * M_PI / 180., 0., 0.5 * M_PI);
-    this->support_line_width        = support_material_flow(&print_object, config.layer_height).scaled_width();
-    this->support_roof_line_width   = support_material_interface_flow(&print_object, config.layer_height).scaled_width();
-    //FIXME add it to SlicingParameters and reuse in both tree and normal supports?
-    this->support_bottom_enable     = config.support_material_interface_layers.value > 0 && config.support_material_bottom_interface_layers.value != 0;
-    this->support_bottom_height     = this->support_bottom_enable ?
-        (config.support_material_bottom_interface_layers.value > 0 ?
-            config.support_material_bottom_interface_layers.value :
-            config.support_material_interface_layers.value) * this->layer_height :
-        0;
-    this->support_material_buildplate_only = config.support_material_buildplate_only;
-    this->support_xy_distance       = scaled<coord_t>(config.support_material_xy_spacing.get_abs_value(external_perimeter_width));
-    // Separation of interfaces, it is likely smaller than support_xy_distance.
-    this->support_xy_distance_overhang = std::min(this->support_xy_distance, scaled<coord_t>(0.5 * external_perimeter_width));
-    this->support_top_distance      = scaled<coord_t>(slicing_params.gap_support_object);
-    this->support_bottom_distance   = scaled<coord_t>(slicing_params.gap_object_support);
-//    this->support_interface_skip_height =
-//    this->support_infill_angles     = 
-    this->support_roof_enable       = config.support_material_interface_layers.value > 0;
-    this->support_roof_layers       = this->support_roof_enable ? config.support_material_interface_layers.value : 0;
-    this->support_floor_enable      = config.support_material_interface_layers.value > 0 && config.support_material_bottom_interface_layers.value > 0;
-    this->support_floor_layers      = this->support_floor_enable ? config.support_material_bottom_interface_layers.value : 0;
-//    this->minimum_roof_area         = 
-//    this->support_roof_angles       = 
-    this->support_roof_pattern      = config.support_material_interface_pattern;
-    this->support_pattern           = config.support_material_pattern;
-    this->support_line_spacing      = scaled<coord_t>(config.support_material_spacing.value);
-//    this->support_bottom_offset     = 
-//    this->support_wall_count        = config.support_material_with_sheath ? 1 : 0;
-    this->support_wall_count        = 1;
-    this->support_roof_line_distance = scaled<coord_t>(config.support_material_interface_spacing.value) + this->support_roof_line_width;
-//    this->minimum_support_area      = 
-//    this->minimum_bottom_area       = 
-//    this->support_offset            = 
-    this->support_tree_branch_distance = scaled<coord_t>(config.support_tree_branch_distance.value);
-    this->support_tree_angle          = std::clamp<double>(config.support_tree_angle * M_PI / 180., 0., 0.5 * M_PI - EPSILON);
-    this->support_tree_angle_slow     = std::clamp<double>(config.support_tree_angle_slow * M_PI / 180., 0., this->support_tree_angle - EPSILON);
-    this->support_tree_branch_diameter = scaled<coord_t>(config.support_tree_branch_diameter.value);
-    this->support_tree_branch_diameter_angle = std::clamp<double>(config.support_tree_branch_diameter_angle * M_PI / 180., 0., 0.5 * M_PI - EPSILON);
-    this->support_tree_top_rate       = config.support_tree_top_rate.value; // percent
-//    this->support_tree_tip_diameter = this->support_line_width;
-    this->support_tree_tip_diameter = std::clamp(scaled<coord_t>(config.support_tree_tip_diameter.value), 0, this->support_tree_branch_diameter);
-}
-
 //FIXME Machine border is currently ignored.
 static Polygons calculateMachineBorderCollision(Polygon machine_border)
 {

src/libslic3r/Support/TreeModelVolumes.hpp

@@ -14,6 +14,8 @@
 
 #include <boost/functional/hash.hpp>
 
+#include "TreeSupportCommon.hpp"
+
 #include "../Point.hpp"
 #include "../Polygon.hpp"
 #include "../PrintConfig.hpp"
@@ -27,176 +29,6 @@ class PrintObject;
 namespace FFFTreeSupport
 {
 
-using LayerIndex = int;
-
-struct TreeSupportMeshGroupSettings {
-    TreeSupportMeshGroupSettings() = default;
-    explicit TreeSupportMeshGroupSettings(const PrintObject &print_object);
-
-/*********************************************************************/
-/* Print parameters, not support specific:                           */
-/*********************************************************************/
-    coord_t                         layer_height                            { scaled<coord_t>(0.15) };
-    // Maximum Deviation (meshfix_maximum_deviation)
-    // The maximum deviation allowed when reducing the resolution for the Maximum Resolution setting. If you increase this, 
-    // the print will be less accurate, but the g-code will be smaller. Maximum Deviation is a limit for Maximum Resolution, 
-    // so if the two conflict the Maximum Deviation will always be held true.
-    coord_t                         resolution                              { scaled<coord_t>(0.025) };
-    // Minimum Feature Size (aka minimum line width) - Arachne specific
-    // Minimum thickness of thin features. Model features that are thinner than this value will not be printed, while features thicker 
-    // than the Minimum Feature Size will be widened to the Minimum Wall Line Width.
-    coord_t                         min_feature_size                        { scaled<coord_t>(0.1) };
-
-/*********************************************************************/
-/* General support parameters:                                       */
-/*********************************************************************/
-
-    // Support Overhang Angle
-    // The minimum angle of overhangs for which support is added. At a value of 0° all overhangs are supported, 90° will not provide any support.
-    double                          support_angle                           { 50. * M_PI / 180. };
-    // Support Line Width
-    // Width of a single support structure line.
-    coord_t                         support_line_width                      { scaled<coord_t>(0.4) };
-    // Support Roof Line Width: Width of a single support roof line.
-    coord_t                         support_roof_line_width                 { scaled<coord_t>(0.4) };
-    // Enable Support Floor (aka bottom interfaces)
-    // Generate a dense slab of material between the bottom of the support and the model. This will create a skin between the model and support.
-    bool                            support_bottom_enable                   { false };
-    // Support Floor Thickness
-    // The thickness of the support floors. This controls the number of dense layers that are printed on top of places of a model on which support rests.
-    coord_t                         support_bottom_height                   { scaled<coord_t>(1.) };
-    bool                            support_material_buildplate_only        { false };
-    // Support X/Y Distance
-    // Distance of the support structure from the print in the X/Y directions.
-    // minimum: 0, maximum warning: 1.5 * machine_nozzle_tip_outer_diameter
-    coord_t                         support_xy_distance                     { scaled<coord_t>(0.7) };
-    // Minimum Support X/Y Distance
-    // Distance of the support structure from the overhang in the X/Y directions.
-    // minimum_value: 0,  minimum warning": support_xy_distance - support_line_width * 2, maximum warning: support_xy_distance
-    coord_t                         support_xy_distance_overhang            { scaled<coord_t>(0.2) };
-    // Support Top Distance
-    // Distance from the top of the support to the print.
-    coord_t                         support_top_distance                    { scaled<coord_t>(0.1) };
-    // Support Bottom Distance
-    // Distance from the print to the bottom of the support.
-    coord_t                         support_bottom_distance                 { scaled<coord_t>(0.1) };
-    //FIXME likely not needed, optimization for clipping of interface layers
-    // When checking where there's model above and below the support, take steps of the given height. Lower values will slice slower, while higher values 
-    // may cause normal support to be printed in some places where there should have been support interface.
-    coord_t                         support_interface_skip_height           { scaled<coord_t>(0.3) };
-    // Support Infill Line Directions
-    // A list of integer line directions to use. Elements from the list are used sequentially as the layers progress and when the end 
-    // of the list is reached, it starts at the beginning again. The list items are separated by commas and the whole list is contained 
-    // in square brackets. Default is an empty list which means use the default angle 0 degrees.
-//    std::vector<double>             support_infill_angles                   {};
-    // Enable Support Roof
-    // Generate a dense slab of material between the top of support and the model. This will create a skin between the model and support.
-    bool                            support_roof_enable                     { false };
-    // Support Roof Thickness
-    // The thickness of the support roofs. This controls the amount of dense layers at the top of the support on which the model rests.
-    coord_t                         support_roof_layers                     { 2 };
-    bool                            support_floor_enable                    { false };
-    coord_t                         support_floor_layers                    { 2 };
-    // Minimum Support Roof Area
-    // Minimum area size for the roofs of the support. Polygons which have an area smaller than this value will be printed as normal support.
-    double                          minimum_roof_area                       { scaled<double>(scaled<double>(1.)) };
-    // A list of integer line directions to use. Elements from the list are used sequentially as the layers progress 
-    // and when the end of the list is reached, it starts at the beginning again. The list items are separated
-    // by commas and the whole list is contained in square brackets. Default is an empty list which means
-    // use the default angles (alternates between 45 and 135 degrees if interfaces are quite thick or 90 degrees).
-    std::vector<double>             support_roof_angles                     {};
-    // Support Roof Pattern (aka top interface)
-    // The pattern with which the roofs of the support are printed.
-    SupportMaterialInterfacePattern support_roof_pattern                    { smipAuto };
-    // Support Pattern
-    // The pattern of the support structures of the print. The different options available result in sturdy or easy to remove support.
-    SupportMaterialPattern          support_pattern                         { smpRectilinear };
-    // Support Line Distance
-    // Distance between the printed support structure lines. This setting is calculated by the support density.
-    coord_t                         support_line_spacing                    { scaled<coord_t>(2.66 - 0.4) };
-    // Support Floor Horizontal Expansion
-    // Amount of offset applied to the floors of the support.
-    coord_t                         support_bottom_offset                   { scaled<coord_t>(0.) };
-    // Support Wall Line Count
-    // The number of walls with which to surround support infill. Adding a wall can make support print more reliably 
-    // and can support overhangs better, but increases print time and material used.
-    // tree: 1, zig-zag: 0, concentric: 1
-    int                             support_wall_count                      { 1 };
-    // Support Roof Line Distance
-    // Distance between the printed support roof lines. This setting is calculated by the Support Roof Density, but can be adjusted separately.
-    coord_t                         support_roof_line_distance              { scaled<coord_t>(0.4) };
-    // Minimum Support Area
-    // Minimum area size for support polygons. Polygons which have an area smaller than this value will not be generated.
-    coord_t                         minimum_support_area                    { scaled<coord_t>(0.) };
-    // Minimum Support Floor Area
-    // Minimum area size for the floors of the support. Polygons which have an area smaller than this value will be printed as normal support.
-    coord_t                         minimum_bottom_area                     { scaled<coord_t>(1.0) };
-    // Support Horizontal Expansion
-    // Amount of offset applied to all support polygons in each layer. Positive values can smooth out the support areas and result in more sturdy support.
-    coord_t                         support_offset                          { scaled<coord_t>(0.) };
-
-/*********************************************************************/
-/* Parameters for the Cura tree supports implementation:             */
-/*********************************************************************/
-
-    // Tree Support Maximum Branch Angle
-    // The maximum angle of the branches, when the branches have to avoid the model. Use a lower angle to make them more vertical and more stable. Use a higher angle to be able to have more reach.
-    // minimum: 0, minimum warning: 20, maximum: 89, maximum warning": 85
-    double                          support_tree_angle                      { 60. * M_PI / 180. };
-    // Tree Support Branch Diameter Angle
-    // The angle of the branches' diameter as they gradually become thicker towards the bottom. An angle of 0 will cause the branches to have uniform thickness over their length. 
-    // A bit of an angle can increase stability of the tree support.
-    // minimum: 0, maximum: 89.9999, maximum warning: 15
-    double                          support_tree_branch_diameter_angle      { 5.  * M_PI / 180. };
-    // Tree Support Branch Distance
-    // How far apart the branches need to be when they touch the model. Making this distance small will cause 
-    // the tree support to touch the model at more points, causing better overhang but making support harder to remove.
-    coord_t                         support_tree_branch_distance            { scaled<coord_t>(1.) };
-    // Tree Support Branch Diameter
-    // The diameter of the thinnest branches of tree support. Thicker branches are more sturdy. Branches towards the base will be thicker than this.
-    // minimum: 0.001, minimum warning: support_line_width * 2
-    coord_t                         support_tree_branch_diameter            { scaled<coord_t>(2.) };
-
-/*********************************************************************/
-/* Parameters new to the Thomas Rahm's tree supports implementation: */
-/*********************************************************************/
-
-    // Tree Support Preferred Branch Angle
-    // The preferred angle of the branches, when they do not have to avoid the model. Use a lower angle to make them more vertical and more stable. Use a higher angle for branches to merge faster.
-    // minimum: 0, minimum warning: 10, maximum: support_tree_angle, maximum warning: support_tree_angle-1
-    double                          support_tree_angle_slow                 { 50. * M_PI / 180. };
-    // Tree Support Diameter Increase To Model
-    // The most the diameter of a branch that has to connect to the model may increase by merging with branches that could reach the buildplate.
-    // Increasing this reduces print time, but increases the area of support that rests on model
-    // minimum: 0
-    coord_t                         support_tree_max_diameter_increase_by_merges_when_support_to_model { scaled<coord_t>(1.0) };
-    // Tree Support Minimum Height To Model
-    // How tall a branch has to be if it is placed on the model. Prevents small blobs of support. This setting is ignored when a branch is supporting a support roof.
-    // minimum: 0, maximum warning: 5
-    coord_t                         support_tree_min_height_to_model        { scaled<coord_t>(1.0) };
-    // Tree Support Inital Layer Diameter
-    // Diameter every branch tries to achieve when reaching the buildplate. Improves bed adhesion.
-    // minimum: 0, maximum warning: 20
-    coord_t                         support_tree_bp_diameter                { scaled<coord_t>(7.5) };
-    // Tree Support Branch Density
-    // Adjusts the density of the support structure used to generate the tips of the branches. A higher value results in better overhangs,
-    // but the supports are harder to remove. Use Support Roof for very high values or ensure support density is similarly high at the top.
-    // ->
-    // Adjusts the density of the support structure used to generate the tips of the branches.
-    // A higher value results in better overhangs but the supports are harder to remove, thus it is recommended to enable top support interfaces
-    // instead of a high branch density value if dense interfaces are needed.
-    // 5%-35%
-    double                          support_tree_top_rate                   { 15. };
-    // Tree Support Tip Diameter
-    // The diameter of the top of the tip of the branches of tree support.
-    // minimum: min_wall_line_width, minimum warning: min_wall_line_width+0.05, maximum_value: support_tree_branch_diameter, value: support_line_width
-    coord_t                         support_tree_tip_diameter               { scaled<coord_t>(0.4) };
-
-    // Support Interface Priority
-    // How support interface and support will interact when they overlap. Currently only implemented for support roof.
-    //enum                           support_interface_priority { support_lines_overwrite_interface_area };
-};
-
 class TreeModelVolumes
 {
 public:

src/libslic3r/Support/TreeSupport.hpp

@@ -9,14 +9,16 @@
 #ifndef slic3r_TreeSupport_hpp
 #define slic3r_TreeSupport_hpp
 
+#include "SupportLayer.hpp"
 #include "TreeModelVolumes.hpp"
-#include "Point.hpp"
+#include "TreeSupportCommon.hpp"
-#include "Support/SupportLayer.hpp"
+
+#include "../BoundingBox.hpp"
+#include "../Point.hpp"
+#include "../Utils.hpp"
 
 #include <boost/container/small_vector.hpp>
 
-#include "BoundingBox.hpp"
-#include "Utils.hpp"
 
 // #define TREE_SUPPORT_SHOW_ERRORS
 
@@ -45,8 +47,6 @@ struct SlicingParameters;
 namespace FFFTreeSupport
 {
 
-using LayerIndex = int;
-
 static constexpr const double  SUPPORT_TREE_EXPONENTIAL_FACTOR = 1.5;
 static constexpr const coord_t SUPPORT_TREE_EXPONENTIAL_THRESHOLD = scaled<coord_t>(1. * SUPPORT_TREE_EXPONENTIAL_FACTOR);
 static constexpr const coord_t SUPPORT_TREE_COLLISION_RESOLUTION = scaled<coord_t>(0.5);
@@ -55,15 +55,6 @@ static constexpr const coord_t SUPPORT_TREE_COLLISION_RESOLUTION = scaled<coord_
 static constexpr const size_t SUPPORT_TREE_CIRCLE_RESOLUTION = 25;
 static constexpr const bool SUPPORT_TREE_AVOID_SUPPORT_BLOCKER = true;
 
-enum class InterfacePreference
-{
-    InterfaceAreaOverwritesSupport,
-    SupportAreaOverwritesInterface,
-    InterfaceLinesOverwriteSupport,
-    SupportLinesOverwriteInterface,
-    Nothing
-};
-
 struct AreaIncreaseSettings
 {
     AreaIncreaseSettings(
@@ -89,8 +80,6 @@ struct AreaIncreaseSettings
     }
 };
 
-struct TreeSupportSettings;
-
 #define TREE_SUPPORTS_TRACK_LOST
 
 // C++17 does not support in place initializers of bit values, thus a constructor zeroing the bits is provided.
@@ -232,6 +221,38 @@ struct SupportElementState : public SupportElementStateBits
     [[nodiscard]] bool locked() const { return this->distance_to_top < this->dont_move_until; }
 };
 
+/*!
+ * \brief Get the Distance to top regarding the real radius this part will have. This is different from distance_to_top, which is can be used to calculate the top most layer of the branch.
+ * \param elem[in] The SupportElement one wants to know the effectiveDTT
+ * \return The Effective DTT.
+ */
+[[nodiscard]] inline size_t getEffectiveDTT(const TreeSupportSettings &settings, const SupportElementState &elem)
+{
+    return elem.effective_radius_height < settings.increase_radius_until_layer ? 
+        (elem.distance_to_top < settings.increase_radius_until_layer ? elem.distance_to_top : settings.increase_radius_until_layer) : 
+        elem.effective_radius_height;
+}
+
+/*!
+ * \brief Get the Radius, that this element will have.
+ * \param elem[in] The Element.
+ * \return The radius the element has.
+ */
+[[nodiscard]] inline coord_t getRadius(const TreeSupportSettings &settings, const SupportElementState &elem)
+{ 
+    return settings.getRadius(getEffectiveDTT(settings, elem), elem.elephant_foot_increases);
+}
+
+/*!
+ * \brief Get the collision Radius of this Element. This can be smaller then the actual radius, as the drawAreas will cut off areas that may collide with the model.
+ * \param elem[in] The Element.
+ * \return The collision radius the element has.
+ */
+[[nodiscard]] inline coord_t getCollisionRadius(const TreeSupportSettings &settings, const SupportElementState &elem)
+{
+    return settings.getRadius(elem.effective_radius_height, elem.elephant_foot_increases);
+}
+
 struct SupportElement
 {
     using ParentIndices =
@@ -262,281 +283,12 @@ struct SupportElement
     Polygons                    influence_area;
 };
 
-/*!
+using SupportElements = std::deque<SupportElement>;
- * \brief This struct contains settings used in the tree support. Thanks to this most functions do not need to know of meshes etc. Also makes the code shorter.
+
- */
+[[nodiscard]] inline coord_t getRadius(const TreeSupportSettings &settings, const SupportElement &elem)
-struct TreeSupportSettings
 {
-    TreeSupportSettings() = default; // required for the definition of the config variable in the TreeSupportGenerator class.
+    return getRadius(settings, elem.state);
-    explicit TreeSupportSettings(const TreeSupportMeshGroupSettings &mesh_group_settings, const SlicingParameters &slicing_params);
+}
-
-private:
-    double angle;
-    double angle_slow;
-    std::vector<coord_t> known_z;
-
-public:
-    // some static variables dependent on other meshes that are not currently processed.
-    // Has to be static because TreeSupportConfig will be used in TreeModelVolumes as this reduces redundancy.
-    inline static bool soluble = false;
-    /*!
-     * \brief Width of a single line of support.
-     */
-    coord_t support_line_width;
-    /*!
-     * \brief Height of a single layer
-     */
-    coord_t layer_height;
-    /*!
-     * \brief Radius of a branch when it has left the tip.
-     */
-    coord_t branch_radius;
-    /*!
-     * \brief smallest allowed radius, required to ensure that even at DTT 0 every circle will still be printed
-     */
-    coord_t min_radius;
-    /*!
-     * \brief How far an influence area may move outward every layer at most.
-     */
-    coord_t maximum_move_distance;
-    /*!
-     * \brief How far every influence area will move outward every layer if possible.
-     */
-    coord_t maximum_move_distance_slow;
-    /*!
-     * \brief Amount of bottom layers. 0 if disabled.
-     */
-    size_t support_bottom_layers;
-    /*!
-     * \brief Amount of effectiveDTT increases are required to reach branch radius.
-     */
-    size_t tip_layers;
-    /*!
-     * \brief How much a branch radius increases with each layer to guarantee the prescribed tree widening.
-     */
-    double branch_radius_increase_per_layer;
-    /*!
-     * \brief How much a branch resting on the model may grow in radius by merging with branches that can reach the buildplate.
-     */
-    coord_t max_to_model_radius_increase;
-    /*!
-     * \brief If smaller (in layers) than that, all branches to model will be deleted
-     */
-    size_t min_dtt_to_model;
-    /*!
-     * \brief Increase radius in the resulting drawn branches, even if the avoidance does not allow it. Will be cut later to still fit.
-     */
-    coord_t increase_radius_until_radius;
-    /*!
-     * \brief Same as increase_radius_until_radius, but contains the DTT at which the radius will be reached.
-     */
-    size_t increase_radius_until_layer;
-    /*!
-     * \brief True if the branches may connect to the model.
-     */
-    bool support_rests_on_model;
-    /*!
-     * \brief How far should support be from the model.
-     */
-    coord_t xy_distance;
-    /*!
-     * \brief A minimum radius a tree trunk should expand to at the buildplate if possible.
-     */
-    coord_t bp_radius;
-    /*!
-     * \brief The layer index at which an increase in radius may be required to reach the bp_radius.
-     */
-    LayerIndex layer_start_bp_radius;
-    /*!
-     * \brief How much one is allowed to increase the tree branch radius close to print bed to reach the required bp_radius at layer 0.
-     * Note that this radius increase will not happen in the tip, to ensure the tip is structurally sound.
-     */
-    double bp_radius_increase_per_layer;
-    /*!
-     * \brief minimum xy_distance. Only relevant when Z overrides XY, otherwise equal to xy_distance-
-     */
-    coord_t xy_min_distance;
-    /*!
-     * \brief Amount of layers distance required the top of the support to the model
-     */
-    size_t z_distance_top_layers;
-    /*!
-     * \brief Amount of layers distance required from the top of the model to the bottom of a support structure.
-     */
-    size_t z_distance_bottom_layers;
-    /*!
-     * \brief User specified angles for the support infill.
-     */
-//        std::vector<double> support_infill_angles;
-    /*!
-     * \brief User specified angles for the support roof infill.
-     */
-    std::vector<double> support_roof_angles;
-    /*!
-     * \brief Pattern used in the support roof. May contain non relevant data if support roof is disabled.
-     */
-    SupportMaterialInterfacePattern roof_pattern;
-    /*!
-     * \brief Pattern used in the support infill.
-     */
-    SupportMaterialPattern support_pattern;
-    /*!
-     * \brief Line width of the support roof.
-     */
-    coord_t support_roof_line_width;
-    /*!
-     * \brief Distance between support infill lines.
-     */
-    coord_t support_line_spacing;
-    /*!
-     * \brief Offset applied to the support floor area.
-     */
-    coord_t support_bottom_offset;
-    /*
-     * \brief Amount of walls the support area will have.
-     */
-    int support_wall_count;
-    /*
-     * \brief Maximum allowed deviation when simplifying.
-     */
-    coord_t resolution;
-    /*
-     * \brief Distance between the lines of the roof.
-     */
-    coord_t support_roof_line_distance;
-    /*
-     * \brief How overlaps of an interface area with a support area should be handled.
-     */
-    InterfacePreference interface_preference;
-
-    /*
-     * \brief The infill class wants a settings object. This one will be the correct one for all settings it uses.
-     */
-    TreeSupportMeshGroupSettings settings;
-
-    /*
-     * \brief Minimum thickness of any model features.
-     */
-    coord_t min_feature_size;
-
-    // Extra raft layers below the object.
-    std::vector<coordf_t> raft_layers;
-
-  public:
-    bool operator==(const TreeSupportSettings& other) const
-    {
-        return branch_radius == other.branch_radius && tip_layers == other.tip_layers && branch_radius_increase_per_layer == other.branch_radius_increase_per_layer && layer_start_bp_radius == other.layer_start_bp_radius && bp_radius == other.bp_radius && 
-               // as a recalculation of the collision areas is required to set a new min_radius.
-               bp_radius_increase_per_layer == other.bp_radius_increase_per_layer && min_radius == other.min_radius && xy_min_distance == other.xy_min_distance &&
-               xy_distance - xy_min_distance == other.xy_distance - other.xy_min_distance && // if the delta of xy_min_distance and xy_distance is different the collision areas have to be recalculated.
-               support_rests_on_model == other.support_rests_on_model && increase_radius_until_layer == other.increase_radius_until_layer && min_dtt_to_model == other.min_dtt_to_model && max_to_model_radius_increase == other.max_to_model_radius_increase && maximum_move_distance == other.maximum_move_distance && maximum_move_distance_slow == other.maximum_move_distance_slow && z_distance_bottom_layers == other.z_distance_bottom_layers && support_line_width == other.support_line_width && 
-               support_line_spacing == other.support_line_spacing && support_roof_line_width == other.support_roof_line_width && // can not be set on a per-mesh basis currently, so code to enable processing different roof line width in the same iteration seems useless.
-               support_bottom_offset == other.support_bottom_offset && support_wall_count == other.support_wall_count && support_pattern == other.support_pattern && roof_pattern == other.roof_pattern && // can not be set on a per-mesh basis currently, so code to enable processing different roof patterns in the same iteration seems useless.
-               support_roof_angles == other.support_roof_angles && 
-               //support_infill_angles == other.support_infill_angles && 
-               increase_radius_until_radius == other.increase_radius_until_radius && support_bottom_layers == other.support_bottom_layers && layer_height == other.layer_height && z_distance_top_layers == other.z_distance_top_layers && resolution == other.resolution && // Infill generation depends on deviation and resolution.
-               support_roof_line_distance == other.support_roof_line_distance && interface_preference == other.interface_preference
-               && min_feature_size == other.min_feature_size // interface_preference should be identical to ensure the tree will correctly interact with the roof.
-               // The infill class now wants the settings object and reads a lot of settings, and as the infill class is used to calculate support roof lines for interface-preference. Not all of these may be required to be identical, but as I am not sure, better safe than sorry
-#if 0
-                && (interface_preference == InterfacePreference::InterfaceAreaOverwritesSupport || interface_preference == InterfacePreference::SupportAreaOverwritesInterface
-                // Perimeter generator parameters
-                   || 
-                        (settings.get<bool>("fill_outline_gaps") == other.settings.get<bool>("fill_outline_gaps") && 
-                         settings.get<coord_t>("min_bead_width") == other.settings.get<coord_t>("min_bead_width") && 
-                         settings.get<double>("wall_transition_angle") == other.settings.get<double>("wall_transition_angle") && 
-                         settings.get<coord_t>("wall_transition_length") == other.settings.get<coord_t>("wall_transition_length") && 
-                         settings.get<Ratio>("wall_split_middle_threshold") == other.settings.get<Ratio>("wall_split_middle_threshold") && 
-                         settings.get<Ratio>("wall_add_middle_threshold") == other.settings.get<Ratio>("wall_add_middle_threshold") && 
-                         settings.get<int>("wall_distribution_count") == other.settings.get<int>("wall_distribution_count") && 
-                         settings.get<coord_t>("wall_transition_filter_distance") == other.settings.get<coord_t>("wall_transition_filter_distance") && 
-                         settings.get<coord_t>("wall_transition_filter_deviation") == other.settings.get<coord_t>("wall_transition_filter_deviation") && 
-                         settings.get<coord_t>("wall_line_width_x") == other.settings.get<coord_t>("wall_line_width_x") && 
-                         settings.get<int>("meshfix_maximum_extrusion_area_deviation") == other.settings.get<int>("meshfix_maximum_extrusion_area_deviation"))
-                    )
-#endif
-               && raft_layers == other.raft_layers
-            ;
-    }
-
-    /*!
-     * \brief Get the Distance to top regarding the real radius this part will have. This is different from distance_to_top, which is can be used to calculate the top most layer of the branch.
-     * \param elem[in] The SupportElement one wants to know the effectiveDTT
-     * \return The Effective DTT.
-     */
-    [[nodiscard]] inline size_t getEffectiveDTT(const SupportElementState &elem) const
-    {
-        return elem.effective_radius_height < increase_radius_until_layer ? (elem.distance_to_top < increase_radius_until_layer ? elem.distance_to_top : increase_radius_until_layer) : elem.effective_radius_height;
-    }
-
-    /*!
-     * \brief Get the Radius part will have based on numeric values.
-     * \param distance_to_top[in] The effective distance_to_top of the element
-     * \param elephant_foot_increases[in] The elephant_foot_increases of the element.
-     * \return The radius an element with these attributes would have.
-     */
-    [[nodiscard]] inline coord_t getRadius(size_t distance_to_top, const double elephant_foot_increases = 0) const
-    {
-        return (distance_to_top <= tip_layers ? min_radius + (branch_radius - min_radius) * distance_to_top / tip_layers : // tip
-                       branch_radius + // base
-                       (distance_to_top - tip_layers) * branch_radius_increase_per_layer)
-               + // gradual increase
-               elephant_foot_increases * (std::max(bp_radius_increase_per_layer - branch_radius_increase_per_layer, 0.0));
-    }
-
-    /*!
-     * \brief Get the Radius, that this element will have.
-     * \param elem[in] The Element.
-     * \return The radius the element has.
-     */
-    [[nodiscard]] inline coord_t getRadius(const SupportElementState &elem) const
-        { return getRadius(getEffectiveDTT(elem), elem.elephant_foot_increases); }
-    [[nodiscard]] inline coord_t getRadius(const SupportElement &elem) const
-        { return this->getRadius(elem.state); }
-
-    /*!
-     * \brief Get the collision Radius of this Element. This can be smaller then the actual radius, as the drawAreas will cut off areas that may collide with the model.
-     * \param elem[in] The Element.
-     * \return The collision radius the element has.
-     */
-    [[nodiscard]] inline coord_t getCollisionRadius(const SupportElementState &elem) const
-    {
-        return getRadius(elem.effective_radius_height, elem.elephant_foot_increases);
-    }
-
-    /*!
-     * \brief Get the Radius an element should at least have at a given layer.
-     * \param layer_idx[in] The layer.
-     * \return The radius every element should aim to achieve.
-     */
-    [[nodiscard]] inline coord_t recommendedMinRadius(LayerIndex layer_idx) const
-    {
-        double num_layers_widened = layer_start_bp_radius - layer_idx;
-        return num_layers_widened > 0 ? branch_radius + num_layers_widened * bp_radius_increase_per_layer : 0;
-    }
-
-    /*!
-     * \brief Return on which z in microns the layer will be printed. Used only for support infill line generation.
-     * \param layer_idx[in] The layer.
-     * \return The radius every element should aim to achieve.
-     */
-    [[nodiscard]] inline coord_t getActualZ(LayerIndex layer_idx)
-    {
-        return layer_idx < coord_t(known_z.size()) ? known_z[layer_idx] : (layer_idx - known_z.size()) * layer_height + known_z.size() ? known_z.back() : 0;
-    }
-
-    /*!
-     * \brief Set the z every Layer is printed at. Required for getActualZ to work
-     * \param z[in] The z every LayerIndex is printed. Vector is used as a map<LayerIndex,coord_t> with the index of each element being the corresponding LayerIndex
-     * \return The radius every element should aim to achieve.
-     */
-    void setActualZ(std::vector<coord_t>& z)
-    {
-        known_z = z;
-    }
-};
-
-void tree_supports_show_error(std::string_view message, bool critical);
 
 } // namespace FFFTreeSupport
 

src/libslic3r/Support/TreeSupportCommon.cpp

@@ -0,0 +1,190 @@
+// Tree supports by Thomas Rahm, losely based on Tree Supports by CuraEngine.
+// Original source of Thomas Rahm's tree supports:
+// https://github.com/ThomasRahm/CuraEngine
+//
+// Original CuraEngine copyright:
+// Copyright (c) 2021 Ultimaker B.V.
+// CuraEngine is released under the terms of the AGPLv3 or higher.
+
+#include "TreeSupportCommon.hpp"
+
+namespace Slic3r::FFFTreeSupport {
+
+TreeSupportMeshGroupSettings::TreeSupportMeshGroupSettings(const PrintObject &print_object)
+{
+    const PrintConfig       &print_config       = print_object.print()->config();
+    const PrintObjectConfig &config             = print_object.config();
+    const SlicingParameters &slicing_params     = print_object.slicing_parameters();
+//    const std::vector<unsigned int>  printing_extruders = print_object.object_extruders();
+
+    // Support must be enabled and set to Tree style.
+    assert(config.support_material || config.support_material_enforce_layers > 0);
+    assert(config.support_material_style == smsTree || config.support_material_style == smsOrganic);
+
+    // Calculate maximum external perimeter width over all printing regions, taking into account the default layer height.
+    coordf_t external_perimeter_width = 0.;
+    for (size_t region_id = 0; region_id < print_object.num_printing_regions(); ++ region_id) {
+        const PrintRegion &region = print_object.printing_region(region_id);
+        external_perimeter_width = std::max<coordf_t>(external_perimeter_width, region.flow(print_object, frExternalPerimeter, config.layer_height).width());
+    }
+
+    this->layer_height              = scaled<coord_t>(config.layer_height.value);
+    this->resolution                = scaled<coord_t>(print_config.gcode_resolution.value);
+    // Arache feature
+    this->min_feature_size          = scaled<coord_t>(config.min_feature_size.value);
+    // +1 makes the threshold inclusive
+    this->support_angle             = 0.5 * M_PI - std::clamp<double>((config.support_material_threshold + 1) * M_PI / 180., 0., 0.5 * M_PI);
+    this->support_line_width        = support_material_flow(&print_object, config.layer_height).scaled_width();
+    this->support_roof_line_width   = support_material_interface_flow(&print_object, config.layer_height).scaled_width();
+    //FIXME add it to SlicingParameters and reuse in both tree and normal supports?
+    this->support_bottom_enable     = config.support_material_interface_layers.value > 0 && config.support_material_bottom_interface_layers.value != 0;
+    this->support_bottom_height     = this->support_bottom_enable ?
+        (config.support_material_bottom_interface_layers.value > 0 ?
+            config.support_material_bottom_interface_layers.value :
+            config.support_material_interface_layers.value) * this->layer_height :
+        0;
+    this->support_material_buildplate_only = config.support_material_buildplate_only;
+    this->support_xy_distance       = scaled<coord_t>(config.support_material_xy_spacing.get_abs_value(external_perimeter_width));
+    // Separation of interfaces, it is likely smaller than support_xy_distance.
+    this->support_xy_distance_overhang = std::min(this->support_xy_distance, scaled<coord_t>(0.5 * external_perimeter_width));
+    this->support_top_distance      = scaled<coord_t>(slicing_params.gap_support_object);
+    this->support_bottom_distance   = scaled<coord_t>(slicing_params.gap_object_support);
+//    this->support_interface_skip_height =
+//    this->support_infill_angles     = 
+    this->support_roof_enable       = config.support_material_interface_layers.value > 0;
+    this->support_roof_layers       = this->support_roof_enable ? config.support_material_interface_layers.value : 0;
+    this->support_floor_enable      = config.support_material_interface_layers.value > 0 && config.support_material_bottom_interface_layers.value > 0;
+    this->support_floor_layers      = this->support_floor_enable ? config.support_material_bottom_interface_layers.value : 0;
+//    this->minimum_roof_area         = 
+//    this->support_roof_angles       = 
+    this->support_roof_pattern      = config.support_material_interface_pattern;
+    this->support_pattern           = config.support_material_pattern;
+    this->support_line_spacing      = scaled<coord_t>(config.support_material_spacing.value);
+//    this->support_bottom_offset     = 
+//    this->support_wall_count        = config.support_material_with_sheath ? 1 : 0;
+    this->support_wall_count        = 1;
+    this->support_roof_line_distance = scaled<coord_t>(config.support_material_interface_spacing.value) + this->support_roof_line_width;
+//    this->minimum_support_area      = 
+//    this->minimum_bottom_area       = 
+//    this->support_offset            = 
+    this->support_tree_branch_distance = scaled<coord_t>(config.support_tree_branch_distance.value);
+    this->support_tree_angle          = std::clamp<double>(config.support_tree_angle * M_PI / 180., 0., 0.5 * M_PI - EPSILON);
+    this->support_tree_angle_slow     = std::clamp<double>(config.support_tree_angle_slow * M_PI / 180., 0., this->support_tree_angle - EPSILON);
+    this->support_tree_branch_diameter = scaled<coord_t>(config.support_tree_branch_diameter.value);
+    this->support_tree_branch_diameter_angle = std::clamp<double>(config.support_tree_branch_diameter_angle * M_PI / 180., 0., 0.5 * M_PI - EPSILON);
+    this->support_tree_top_rate       = config.support_tree_top_rate.value; // percent
+//    this->support_tree_tip_diameter = this->support_line_width;
+    this->support_tree_tip_diameter = std::clamp(scaled<coord_t>(config.support_tree_tip_diameter.value), 0, this->support_tree_branch_diameter);
+}
+
+TreeSupportSettings::TreeSupportSettings(const TreeSupportMeshGroupSettings &mesh_group_settings, const SlicingParameters &slicing_params)
+    : angle(mesh_group_settings.support_tree_angle),
+      angle_slow(mesh_group_settings.support_tree_angle_slow),
+      support_line_width(mesh_group_settings.support_line_width),
+      layer_height(mesh_group_settings.layer_height),
+      branch_radius(mesh_group_settings.support_tree_branch_diameter / 2),
+      min_radius(mesh_group_settings.support_tree_tip_diameter / 2), // The actual radius is 50 microns larger as the resulting branches will be increased by 50 microns to avoid rounding errors effectively increasing the xydistance
+      maximum_move_distance((angle < M_PI / 2.) ? (coord_t)(tan(angle) * layer_height) : std::numeric_limits<coord_t>::max()),
+      maximum_move_distance_slow((angle_slow < M_PI / 2.) ? (coord_t)(tan(angle_slow) * layer_height) : std::numeric_limits<coord_t>::max()),
+      support_bottom_layers(mesh_group_settings.support_bottom_enable ? (mesh_group_settings.support_bottom_height + layer_height / 2) / layer_height : 0),
+      tip_layers(std::max((branch_radius - min_radius) / (support_line_width / 3), branch_radius / layer_height)), // Ensure lines always stack nicely even if layer height is large
+      branch_radius_increase_per_layer(tan(mesh_group_settings.support_tree_branch_diameter_angle) * layer_height),
+      max_to_model_radius_increase(mesh_group_settings.support_tree_max_diameter_increase_by_merges_when_support_to_model / 2),
+      min_dtt_to_model(round_up_divide(mesh_group_settings.support_tree_min_height_to_model, layer_height)),
+      increase_radius_until_radius(mesh_group_settings.support_tree_branch_diameter / 2),
+      increase_radius_until_layer(increase_radius_until_radius <= branch_radius ? tip_layers * (increase_radius_until_radius / branch_radius) : (increase_radius_until_radius - branch_radius) / branch_radius_increase_per_layer),
+      support_rests_on_model(! mesh_group_settings.support_material_buildplate_only),
+      xy_distance(mesh_group_settings.support_xy_distance),
+      xy_min_distance(std::min(mesh_group_settings.support_xy_distance, mesh_group_settings.support_xy_distance_overhang)),
+      bp_radius(mesh_group_settings.support_tree_bp_diameter / 2),
+      // Increase by half a line overlap, but not faster than 40 degrees angle (0 degrees means zero increase in radius).
+      bp_radius_increase_per_layer(std::min(tan(0.7) * layer_height, 0.5 * support_line_width)),
+      z_distance_bottom_layers(size_t(round(double(mesh_group_settings.support_bottom_distance) / double(layer_height)))),
+      z_distance_top_layers(size_t(round(double(mesh_group_settings.support_top_distance) / double(layer_height)))),
+//              support_infill_angles(mesh_group_settings.support_infill_angles),
+      support_roof_angles(mesh_group_settings.support_roof_angles),
+      roof_pattern(mesh_group_settings.support_roof_pattern),
+      support_pattern(mesh_group_settings.support_pattern),
+      support_roof_line_width(mesh_group_settings.support_roof_line_width),
+      support_line_spacing(mesh_group_settings.support_line_spacing),
+      support_bottom_offset(mesh_group_settings.support_bottom_offset),
+      support_wall_count(mesh_group_settings.support_wall_count),
+      resolution(mesh_group_settings.resolution),
+      support_roof_line_distance(mesh_group_settings.support_roof_line_distance), // in the end the actual infill has to be calculated to subtract interface from support areas according to interface_preference.
+      settings(mesh_group_settings),
+      min_feature_size(mesh_group_settings.min_feature_size)
+{
+    layer_start_bp_radius = (bp_radius - branch_radius) / bp_radius_increase_per_layer;
+
+    if (TreeSupportSettings::soluble) {
+        // safeOffsetInc can only work in steps of the size xy_min_distance in the worst case => xy_min_distance has to be a bit larger than 0 in this worst case and should be large enough for performance to not suffer extremely
+        // When for all meshes the z bottom and top distance is more than one layer though the worst case is xy_min_distance + min_feature_size
+        // This is not the best solution, but the only one to ensure areas can not lag though walls at high maximum_move_distance.
+        xy_min_distance = std::max(xy_min_distance, scaled<coord_t>(0.1));
+        xy_distance     = std::max(xy_distance, xy_min_distance);
+    }
+
+//            const std::unordered_map<std::string, InterfacePreference> interface_map = { { "support_area_overwrite_interface_area", InterfacePreference::SupportAreaOverwritesInterface }, { "interface_area_overwrite_support_area", InterfacePreference::InterfaceAreaOverwritesSupport }, { "support_lines_overwrite_interface_area", InterfacePreference::SupportLinesOverwriteInterface }, { "interface_lines_overwrite_support_area", InterfacePreference::InterfaceLinesOverwriteSupport }, { "nothing", InterfacePreference::Nothing } };
+//            interface_preference = interface_map.at(mesh_group_settings.get<std::string>("support_interface_priority"));
+//FIXME this was the default
+//            interface_preference = InterfacePreference::SupportLinesOverwriteInterface;
+    //interface_preference = InterfacePreference::SupportAreaOverwritesInterface;
+    interface_preference = InterfacePreference::InterfaceAreaOverwritesSupport;
+
+    if (slicing_params.raft_layers() > 0) {
+        // Fill in raft_layers with the heights of the layers below the first object layer.
+        // First layer
+        double z = slicing_params.first_print_layer_height;
+        this->raft_layers.emplace_back(z);
+        // Raft base layers
+        for (size_t i = 1; i < slicing_params.base_raft_layers; ++ i) {
+            z += slicing_params.base_raft_layer_height;
+            this->raft_layers.emplace_back(z);
+        }
+        // Raft interface layers
+        for (size_t i = 0; i + 1 < slicing_params.interface_raft_layers; ++ i) {
+            z += slicing_params.interface_raft_layer_height;
+            this->raft_layers.emplace_back(z);
+        }
+        // Raft contact layer
+        if (slicing_params.raft_layers() > 1) {
+            z = slicing_params.raft_contact_top_z;
+            this->raft_layers.emplace_back(z);
+        }
+        if (double dist_to_go = slicing_params.object_print_z_min - z; dist_to_go > EPSILON) {
+            // Layers between the raft contacts and bottom of the object.
+            auto nsteps = int(ceil(dist_to_go / slicing_params.max_suport_layer_height));
+            double step = dist_to_go / nsteps;
+            for (size_t i = 0; i < nsteps; ++ i) {
+                z += step;
+                this->raft_layers.emplace_back(z);
+            }
+        }
+    }
+}
+
+#if defined(TREE_SUPPORT_SHOW_ERRORS) && defined(_WIN32)
+    #define TREE_SUPPORT_SHOW_ERRORS_WIN32
+    #include <windows.h>
+#endif
+
+// Shared with generate_support_areas()
+bool g_showed_critical_error = false;
+bool g_showed_performance_warning = false;
+
+void tree_supports_show_error(std::string_view message, bool critical)
+{ // todo Remove!  ONLY FOR PUBLIC BETA!!
+    printf("Error: %s, critical: %d\n", message.data(), int(critical));
+#ifdef TREE_SUPPORT_SHOW_ERRORS_WIN32
+    static bool showed_critical = false;
+    static bool showed_performance = false;
+    auto bugtype = std::string(critical ? " This is a critical bug. It may cause missing or malformed branches.\n" : "This bug should only decrease performance.\n");
+    bool show    = (critical && !g_showed_critical_error) || (!critical && !g_showed_performance_warning);
+    (critical ? g_showed_critical_error : g_showed_performance_warning) = true;
+    if (show)
+        MessageBoxA(nullptr, std::string("TreeSupport_2 MOD detected an error while generating the tree support.\nPlease report this back to me with profile and model.\nRevision 5.0\n" + std::string(message) + "\n" + bugtype).c_str(), 
+            "Bug detected!", MB_OK | MB_SYSTEMMODAL | MB_SETFOREGROUND | MB_ICONWARNING);
+#endif // TREE_SUPPORT_SHOW_ERRORS_WIN32
+}
+
+} // namespace Slic3r::FFFTreeSupport

src/libslic3r/Support/TreeSupportCommon.hpp

@@ -0,0 +1,593 @@
+// Tree supports by Thomas Rahm, losely based on Tree Supports by CuraEngine.
+// Original source of Thomas Rahm's tree supports:
+// https://github.com/ThomasRahm/CuraEngine
+//
+// Original CuraEngine copyright:
+// Copyright (c) 2021 Ultimaker B.V.
+// CuraEngine is released under the terms of the AGPLv3 or higher.
+
+#ifndef slic3r_TreeSupportCommon_hpp
+#define slic3r_TreeSupportCommon_hpp
+
+#include "../libslic3r.h"
+#include "../Polygon.hpp"
+#include "SupportCommon.hpp"
+
+#include <string_view>
+
+using namespace Slic3r::FFFSupport;
+
+namespace Slic3r
+{
+
+namespace FFFTreeSupport
+{
+
+using LayerIndex = int;
+
+enum class InterfacePreference
+{
+    InterfaceAreaOverwritesSupport,
+    SupportAreaOverwritesInterface,
+    InterfaceLinesOverwriteSupport,
+    SupportLinesOverwriteInterface,
+    Nothing
+};
+
+struct TreeSupportMeshGroupSettings {
+    TreeSupportMeshGroupSettings() = default;
+    explicit TreeSupportMeshGroupSettings(const PrintObject &print_object);
+
+/*********************************************************************/
+/* Print parameters, not support specific:                           */
+/*********************************************************************/
+    coord_t                         layer_height                            { scaled<coord_t>(0.15) };
+    // Maximum Deviation (meshfix_maximum_deviation)
+    // The maximum deviation allowed when reducing the resolution for the Maximum Resolution setting. If you increase this, 
+    // the print will be less accurate, but the g-code will be smaller. Maximum Deviation is a limit for Maximum Resolution, 
+    // so if the two conflict the Maximum Deviation will always be held true.
+    coord_t                         resolution                              { scaled<coord_t>(0.025) };
+    // Minimum Feature Size (aka minimum line width) - Arachne specific
+    // Minimum thickness of thin features. Model features that are thinner than this value will not be printed, while features thicker 
+    // than the Minimum Feature Size will be widened to the Minimum Wall Line Width.
+    coord_t                         min_feature_size                        { scaled<coord_t>(0.1) };
+
+/*********************************************************************/
+/* General support parameters:                                       */
+/*********************************************************************/
+
+    // Support Overhang Angle
+    // The minimum angle of overhangs for which support is added. At a value of 0° all overhangs are supported, 90° will not provide any support.
+    double                          support_angle                           { 50. * M_PI / 180. };
+    // Support Line Width
+    // Width of a single support structure line.
+    coord_t                         support_line_width                      { scaled<coord_t>(0.4) };
+    // Support Roof Line Width: Width of a single support roof line.
+    coord_t                         support_roof_line_width                 { scaled<coord_t>(0.4) };
+    // Enable Support Floor (aka bottom interfaces)
+    // Generate a dense slab of material between the bottom of the support and the model. This will create a skin between the model and support.
+    bool                            support_bottom_enable                   { false };
+    // Support Floor Thickness
+    // The thickness of the support floors. This controls the number of dense layers that are printed on top of places of a model on which support rests.
+    coord_t                         support_bottom_height                   { scaled<coord_t>(1.) };
+    bool                            support_material_buildplate_only        { false };
+    // Support X/Y Distance
+    // Distance of the support structure from the print in the X/Y directions.
+    // minimum: 0, maximum warning: 1.5 * machine_nozzle_tip_outer_diameter
+    coord_t                         support_xy_distance                     { scaled<coord_t>(0.7) };
+    // Minimum Support X/Y Distance
+    // Distance of the support structure from the overhang in the X/Y directions.
+    // minimum_value: 0,  minimum warning": support_xy_distance - support_line_width * 2, maximum warning: support_xy_distance
+    coord_t                         support_xy_distance_overhang            { scaled<coord_t>(0.2) };
+    // Support Top Distance
+    // Distance from the top of the support to the print.
+    coord_t                         support_top_distance                    { scaled<coord_t>(0.1) };
+    // Support Bottom Distance
+    // Distance from the print to the bottom of the support.
+    coord_t                         support_bottom_distance                 { scaled<coord_t>(0.1) };
+    //FIXME likely not needed, optimization for clipping of interface layers
+    // When checking where there's model above and below the support, take steps of the given height. Lower values will slice slower, while higher values 
+    // may cause normal support to be printed in some places where there should have been support interface.
+    coord_t                         support_interface_skip_height           { scaled<coord_t>(0.3) };
+    // Support Infill Line Directions
+    // A list of integer line directions to use. Elements from the list are used sequentially as the layers progress and when the end 
+    // of the list is reached, it starts at the beginning again. The list items are separated by commas and the whole list is contained 
+    // in square brackets. Default is an empty list which means use the default angle 0 degrees.
+//    std::vector<double>             support_infill_angles                   {};
+    // Enable Support Roof
+    // Generate a dense slab of material between the top of support and the model. This will create a skin between the model and support.
+    bool                            support_roof_enable                     { false };
+    // Support Roof Thickness
+    // The thickness of the support roofs. This controls the amount of dense layers at the top of the support on which the model rests.
+    coord_t                         support_roof_layers                     { 2 };
+    bool                            support_floor_enable                    { false };
+    coord_t                         support_floor_layers                    { 2 };
+    // Minimum Support Roof Area
+    // Minimum area size for the roofs of the support. Polygons which have an area smaller than this value will be printed as normal support.
+    double                          minimum_roof_area                       { scaled<double>(scaled<double>(1.)) };
+    // A list of integer line directions to use. Elements from the list are used sequentially as the layers progress 
+    // and when the end of the list is reached, it starts at the beginning again. The list items are separated
+    // by commas and the whole list is contained in square brackets. Default is an empty list which means
+    // use the default angles (alternates between 45 and 135 degrees if interfaces are quite thick or 90 degrees).
+    std::vector<double>             support_roof_angles                     {};
+    // Support Roof Pattern (aka top interface)
+    // The pattern with which the roofs of the support are printed.
+    SupportMaterialInterfacePattern support_roof_pattern                    { smipAuto };
+    // Support Pattern
+    // The pattern of the support structures of the print. The different options available result in sturdy or easy to remove support.
+    SupportMaterialPattern          support_pattern                         { smpRectilinear };
+    // Support Line Distance
+    // Distance between the printed support structure lines. This setting is calculated by the support density.
+    coord_t                         support_line_spacing                    { scaled<coord_t>(2.66 - 0.4) };
+    // Support Floor Horizontal Expansion
+    // Amount of offset applied to the floors of the support.
+    coord_t                         support_bottom_offset                   { scaled<coord_t>(0.) };
+    // Support Wall Line Count
+    // The number of walls with which to surround support infill. Adding a wall can make support print more reliably 
+    // and can support overhangs better, but increases print time and material used.
+    // tree: 1, zig-zag: 0, concentric: 1
+    int                             support_wall_count                      { 1 };
+    // Support Roof Line Distance
+    // Distance between the printed support roof lines. This setting is calculated by the Support Roof Density, but can be adjusted separately.
+    coord_t                         support_roof_line_distance              { scaled<coord_t>(0.4) };
+    // Minimum Support Area
+    // Minimum area size for support polygons. Polygons which have an area smaller than this value will not be generated.
+    coord_t                         minimum_support_area                    { scaled<coord_t>(0.) };
+    // Minimum Support Floor Area
+    // Minimum area size for the floors of the support. Polygons which have an area smaller than this value will be printed as normal support.
+    coord_t                         minimum_bottom_area                     { scaled<coord_t>(1.0) };
+    // Support Horizontal Expansion
+    // Amount of offset applied to all support polygons in each layer. Positive values can smooth out the support areas and result in more sturdy support.
+    coord_t                         support_offset                          { scaled<coord_t>(0.) };
+
+/*********************************************************************/
+/* Parameters for the Cura tree supports implementation:             */
+/*********************************************************************/
+
+    // Tree Support Maximum Branch Angle
+    // The maximum angle of the branches, when the branches have to avoid the model. Use a lower angle to make them more vertical and more stable. Use a higher angle to be able to have more reach.
+    // minimum: 0, minimum warning: 20, maximum: 89, maximum warning": 85
+    double                          support_tree_angle                      { 60. * M_PI / 180. };
+    // Tree Support Branch Diameter Angle
+    // The angle of the branches' diameter as they gradually become thicker towards the bottom. An angle of 0 will cause the branches to have uniform thickness over their length. 
+    // A bit of an angle can increase stability of the tree support.
+    // minimum: 0, maximum: 89.9999, maximum warning: 15
+    double                          support_tree_branch_diameter_angle      { 5.  * M_PI / 180. };
+    // Tree Support Branch Distance
+    // How far apart the branches need to be when they touch the model. Making this distance small will cause 
+    // the tree support to touch the model at more points, causing better overhang but making support harder to remove.
+    coord_t                         support_tree_branch_distance            { scaled<coord_t>(1.) };
+    // Tree Support Branch Diameter
+    // The diameter of the thinnest branches of tree support. Thicker branches are more sturdy. Branches towards the base will be thicker than this.
+    // minimum: 0.001, minimum warning: support_line_width * 2
+    coord_t                         support_tree_branch_diameter            { scaled<coord_t>(2.) };
+
+/*********************************************************************/
+/* Parameters new to the Thomas Rahm's tree supports implementation: */
+/*********************************************************************/
+
+    // Tree Support Preferred Branch Angle
+    // The preferred angle of the branches, when they do not have to avoid the model. Use a lower angle to make them more vertical and more stable. Use a higher angle for branches to merge faster.
+    // minimum: 0, minimum warning: 10, maximum: support_tree_angle, maximum warning: support_tree_angle-1
+    double                          support_tree_angle_slow                 { 50. * M_PI / 180. };
+    // Tree Support Diameter Increase To Model
+    // The most the diameter of a branch that has to connect to the model may increase by merging with branches that could reach the buildplate.
+    // Increasing this reduces print time, but increases the area of support that rests on model
+    // minimum: 0
+    coord_t                         support_tree_max_diameter_increase_by_merges_when_support_to_model { scaled<coord_t>(1.0) };
+    // Tree Support Minimum Height To Model
+    // How tall a branch has to be if it is placed on the model. Prevents small blobs of support. This setting is ignored when a branch is supporting a support roof.
+    // minimum: 0, maximum warning: 5
+    coord_t                         support_tree_min_height_to_model        { scaled<coord_t>(1.0) };
+    // Tree Support Inital Layer Diameter
+    // Diameter every branch tries to achieve when reaching the buildplate. Improves bed adhesion.
+    // minimum: 0, maximum warning: 20
+    coord_t                         support_tree_bp_diameter                { scaled<coord_t>(7.5) };
+    // Tree Support Branch Density
+    // Adjusts the density of the support structure used to generate the tips of the branches. A higher value results in better overhangs,
+    // but the supports are harder to remove. Use Support Roof for very high values or ensure support density is similarly high at the top.
+    // ->
+    // Adjusts the density of the support structure used to generate the tips of the branches.
+    // A higher value results in better overhangs but the supports are harder to remove, thus it is recommended to enable top support interfaces
+    // instead of a high branch density value if dense interfaces are needed.
+    // 5%-35%
+    double                          support_tree_top_rate                   { 15. };
+    // Tree Support Tip Diameter
+    // The diameter of the top of the tip of the branches of tree support.
+    // minimum: min_wall_line_width, minimum warning: min_wall_line_width+0.05, maximum_value: support_tree_branch_diameter, value: support_line_width
+    coord_t                         support_tree_tip_diameter               { scaled<coord_t>(0.4) };
+
+    // Support Interface Priority
+    // How support interface and support will interact when they overlap. Currently only implemented for support roof.
+    //enum                           support_interface_priority { support_lines_overwrite_interface_area };
+};
+
+/*!
+ * \brief This struct contains settings used in the tree support. Thanks to this most functions do not need to know of meshes etc. Also makes the code shorter.
+ */
+struct TreeSupportSettings
+{
+public:
+    TreeSupportSettings() = default; // required for the definition of the config variable in the TreeSupportGenerator class.
+    explicit TreeSupportSettings(const TreeSupportMeshGroupSettings &mesh_group_settings, const SlicingParameters &slicing_params);
+
+    // some static variables dependent on other meshes that are not currently processed.
+    // Has to be static because TreeSupportConfig will be used in TreeModelVolumes as this reduces redundancy.
+    inline static bool soluble = false;
+    /*!
+     * \brief Width of a single line of support.
+     */
+    coord_t support_line_width;
+    /*!
+     * \brief Height of a single layer
+     */
+    coord_t layer_height;
+    /*!
+     * \brief Radius of a branch when it has left the tip.
+     */
+    coord_t branch_radius;
+    /*!
+     * \brief smallest allowed radius, required to ensure that even at DTT 0 every circle will still be printed
+     */
+    coord_t min_radius;
+    /*!
+     * \brief How far an influence area may move outward every layer at most.
+     */
+    coord_t maximum_move_distance;
+    /*!
+     * \brief How far every influence area will move outward every layer if possible.
+     */
+    coord_t maximum_move_distance_slow;
+    /*!
+     * \brief Amount of bottom layers. 0 if disabled.
+     */
+    size_t support_bottom_layers;
+    /*!
+     * \brief Amount of effectiveDTT increases are required to reach branch radius.
+     */
+    size_t tip_layers;
+    /*!
+     * \brief How much a branch radius increases with each layer to guarantee the prescribed tree widening.
+     */
+    double branch_radius_increase_per_layer;
+    /*!
+     * \brief How much a branch resting on the model may grow in radius by merging with branches that can reach the buildplate.
+     */
+    coord_t max_to_model_radius_increase;
+    /*!
+     * \brief If smaller (in layers) than that, all branches to model will be deleted
+     */
+    size_t min_dtt_to_model;
+    /*!
+     * \brief Increase radius in the resulting drawn branches, even if the avoidance does not allow it. Will be cut later to still fit.
+     */
+    coord_t increase_radius_until_radius;
+    /*!
+     * \brief Same as increase_radius_until_radius, but contains the DTT at which the radius will be reached.
+     */
+    size_t increase_radius_until_layer;
+    /*!
+     * \brief True if the branches may connect to the model.
+     */
+    bool support_rests_on_model;
+    /*!
+     * \brief How far should support be from the model.
+     */
+    coord_t xy_distance;
+    /*!
+     * \brief A minimum radius a tree trunk should expand to at the buildplate if possible.
+     */
+    coord_t bp_radius;
+    /*!
+     * \brief The layer index at which an increase in radius may be required to reach the bp_radius.
+     */
+    LayerIndex layer_start_bp_radius;
+    /*!
+     * \brief How much one is allowed to increase the tree branch radius close to print bed to reach the required bp_radius at layer 0.
+     * Note that this radius increase will not happen in the tip, to ensure the tip is structurally sound.
+     */
+    double bp_radius_increase_per_layer;
+    /*!
+     * \brief minimum xy_distance. Only relevant when Z overrides XY, otherwise equal to xy_distance-
+     */
+    coord_t xy_min_distance;
+    /*!
+     * \brief Amount of layers distance required the top of the support to the model
+     */
+    size_t z_distance_top_layers;
+    /*!
+     * \brief Amount of layers distance required from the top of the model to the bottom of a support structure.
+     */
+    size_t z_distance_bottom_layers;
+    /*!
+     * \brief User specified angles for the support infill.
+     */
+//        std::vector<double> support_infill_angles;
+    /*!
+     * \brief User specified angles for the support roof infill.
+     */
+    std::vector<double> support_roof_angles;
+    /*!
+     * \brief Pattern used in the support roof. May contain non relevant data if support roof is disabled.
+     */
+    SupportMaterialInterfacePattern roof_pattern;
+    /*!
+     * \brief Pattern used in the support infill.
+     */
+    SupportMaterialPattern support_pattern;
+    /*!
+     * \brief Line width of the support roof.
+     */
+    coord_t support_roof_line_width;
+    /*!
+     * \brief Distance between support infill lines.
+     */
+    coord_t support_line_spacing;
+    /*!
+     * \brief Offset applied to the support floor area.
+     */
+    coord_t support_bottom_offset;
+    /*
+     * \brief Amount of walls the support area will have.
+     */
+    int support_wall_count;
+    /*
+     * \brief Maximum allowed deviation when simplifying.
+     */
+    coord_t resolution;
+    /*
+     * \brief Distance between the lines of the roof.
+     */
+    coord_t support_roof_line_distance;
+    /*
+     * \brief How overlaps of an interface area with a support area should be handled.
+     */
+    InterfacePreference interface_preference;
+
+    /*
+     * \brief The infill class wants a settings object. This one will be the correct one for all settings it uses.
+     */
+    TreeSupportMeshGroupSettings settings;
+
+    /*
+     * \brief Minimum thickness of any model features.
+     */
+    coord_t min_feature_size;
+
+    // Extra raft layers below the object.
+    std::vector<coordf_t> raft_layers;
+
+public:
+    bool operator==(const TreeSupportSettings& other) const
+    {
+        return branch_radius == other.branch_radius && tip_layers == other.tip_layers && branch_radius_increase_per_layer == other.branch_radius_increase_per_layer && layer_start_bp_radius == other.layer_start_bp_radius && bp_radius == other.bp_radius && 
+               // as a recalculation of the collision areas is required to set a new min_radius.
+               bp_radius_increase_per_layer == other.bp_radius_increase_per_layer && min_radius == other.min_radius && xy_min_distance == other.xy_min_distance &&
+               xy_distance - xy_min_distance == other.xy_distance - other.xy_min_distance && // if the delta of xy_min_distance and xy_distance is different the collision areas have to be recalculated.
+               support_rests_on_model == other.support_rests_on_model && increase_radius_until_layer == other.increase_radius_until_layer && min_dtt_to_model == other.min_dtt_to_model && max_to_model_radius_increase == other.max_to_model_radius_increase && maximum_move_distance == other.maximum_move_distance && maximum_move_distance_slow == other.maximum_move_distance_slow && z_distance_bottom_layers == other.z_distance_bottom_layers && support_line_width == other.support_line_width && 
+               support_line_spacing == other.support_line_spacing && support_roof_line_width == other.support_roof_line_width && // can not be set on a per-mesh basis currently, so code to enable processing different roof line width in the same iteration seems useless.
+               support_bottom_offset == other.support_bottom_offset && support_wall_count == other.support_wall_count && support_pattern == other.support_pattern && roof_pattern == other.roof_pattern && // can not be set on a per-mesh basis currently, so code to enable processing different roof patterns in the same iteration seems useless.
+               support_roof_angles == other.support_roof_angles && 
+               //support_infill_angles == other.support_infill_angles && 
+               increase_radius_until_radius == other.increase_radius_until_radius && support_bottom_layers == other.support_bottom_layers && layer_height == other.layer_height && z_distance_top_layers == other.z_distance_top_layers && resolution == other.resolution && // Infill generation depends on deviation and resolution.
+               support_roof_line_distance == other.support_roof_line_distance && interface_preference == other.interface_preference
+               && min_feature_size == other.min_feature_size // interface_preference should be identical to ensure the tree will correctly interact with the roof.
+               // The infill class now wants the settings object and reads a lot of settings, and as the infill class is used to calculate support roof lines for interface-preference. Not all of these may be required to be identical, but as I am not sure, better safe than sorry
+#if 0
+                && (interface_preference == InterfacePreference::InterfaceAreaOverwritesSupport || interface_preference == InterfacePreference::SupportAreaOverwritesInterface
+                // Perimeter generator parameters
+                   || 
+                        (settings.get<bool>("fill_outline_gaps") == other.settings.get<bool>("fill_outline_gaps") && 
+                         settings.get<coord_t>("min_bead_width") == other.settings.get<coord_t>("min_bead_width") && 
+                         settings.get<double>("wall_transition_angle") == other.settings.get<double>("wall_transition_angle") && 
+                         settings.get<coord_t>("wall_transition_length") == other.settings.get<coord_t>("wall_transition_length") && 
+                         settings.get<Ratio>("wall_split_middle_threshold") == other.settings.get<Ratio>("wall_split_middle_threshold") && 
+                         settings.get<Ratio>("wall_add_middle_threshold") == other.settings.get<Ratio>("wall_add_middle_threshold") && 
+                         settings.get<int>("wall_distribution_count") == other.settings.get<int>("wall_distribution_count") && 
+                         settings.get<coord_t>("wall_transition_filter_distance") == other.settings.get<coord_t>("wall_transition_filter_distance") && 
+                         settings.get<coord_t>("wall_transition_filter_deviation") == other.settings.get<coord_t>("wall_transition_filter_deviation") && 
+                         settings.get<coord_t>("wall_line_width_x") == other.settings.get<coord_t>("wall_line_width_x") && 
+                         settings.get<int>("meshfix_maximum_extrusion_area_deviation") == other.settings.get<int>("meshfix_maximum_extrusion_area_deviation"))
+                    )
+#endif
+               && raft_layers == other.raft_layers
+            ;
+    }
+
+    /*!
+     * \brief Get the Radius part will have based on numeric values.
+     * \param distance_to_top[in] The effective distance_to_top of the element
+     * \param elephant_foot_increases[in] The elephant_foot_increases of the element.
+     * \return The radius an element with these attributes would have.
+     */
+    [[nodiscard]] inline coord_t getRadius(size_t distance_to_top, const double elephant_foot_increases = 0) const
+    {
+        return (distance_to_top <= tip_layers ? min_radius + (branch_radius - min_radius) * distance_to_top / tip_layers : // tip
+                       branch_radius + // base
+                       (distance_to_top - tip_layers) * branch_radius_increase_per_layer)
+               + // gradual increase
+               elephant_foot_increases * (std::max(bp_radius_increase_per_layer - branch_radius_increase_per_layer, 0.0));
+    }
+
+    /*!
+     * \brief Get the Radius an element should at least have at a given layer.
+     * \param layer_idx[in] The layer.
+     * \return The radius every element should aim to achieve.
+     */
+    [[nodiscard]] inline coord_t recommendedMinRadius(LayerIndex layer_idx) const
+    {
+        double num_layers_widened = layer_start_bp_radius - layer_idx;
+        return num_layers_widened > 0 ? branch_radius + num_layers_widened * bp_radius_increase_per_layer : 0;
+    }
+
+#if 0
+    /*!
+     * \brief Return on which z in microns the layer will be printed. Used only for support infill line generation.
+     * \param layer_idx[in] The layer.
+     * \return The radius every element should aim to achieve.
+     */
+    [[nodiscard]] inline coord_t getActualZ(LayerIndex layer_idx)
+    {
+        return layer_idx < coord_t(known_z.size()) ? known_z[layer_idx] : (layer_idx - known_z.size()) * layer_height + known_z.size() ? known_z.back() : 0;
+    }
+
+    /*!
+     * \brief Set the z every Layer is printed at. Required for getActualZ to work
+     * \param z[in] The z every LayerIndex is printed. Vector is used as a map<LayerIndex,coord_t> with the index of each element being the corresponding LayerIndex
+     * \return The radius every element should aim to achieve.
+     */
+    void setActualZ(std::vector<coord_t>& z)
+    {
+        known_z = z;
+    }
+#endif
+
+private:
+    double angle;
+    double angle_slow;
+//    std::vector<coord_t> known_z;
+};
+
+static constexpr const bool polygons_strictly_simple = false;
+
+static constexpr const auto tiny_area_threshold = sqr(scaled<double>(0.001));
+
+void tree_supports_show_error(std::string_view message, bool critical);
+
+inline double layer_z(const SlicingParameters &slicing_params, const TreeSupportSettings &config, const size_t layer_idx)
+{
+    return layer_idx >= config.raft_layers.size() ? 
+        slicing_params.object_print_z_min + slicing_params.first_object_layer_height + (layer_idx - config.raft_layers.size()) * slicing_params.layer_height :
+        config.raft_layers[layer_idx];
+}
+// Lowest collision layer
+inline LayerIndex layer_idx_ceil(const SlicingParameters &slicing_params, const TreeSupportSettings &config, const double z)
+{
+    return 
+        LayerIndex(config.raft_layers.size()) +
+        std::max<LayerIndex>(0, ceil((z - slicing_params.object_print_z_min - slicing_params.first_object_layer_height) / slicing_params.layer_height));
+}
+// Highest collision layer
+inline LayerIndex layer_idx_floor(const SlicingParameters &slicing_params, const TreeSupportSettings &config, const double z)
+{
+    return 
+        LayerIndex(config.raft_layers.size()) + 
+        std::max<LayerIndex>(0, floor((z - slicing_params.object_print_z_min - slicing_params.first_object_layer_height) / slicing_params.layer_height));
+}
+
+inline SupportGeneratorLayer& layer_initialize(
+    SupportGeneratorLayer     &layer_new,
+    const SlicingParameters   &slicing_params,
+    const TreeSupportSettings &config, 
+    const size_t               layer_idx)
+{
+    layer_new.print_z  = layer_z(slicing_params, config, layer_idx);
+    layer_new.bottom_z = layer_idx > 0 ? layer_z(slicing_params, config, layer_idx - 1) : 0;
+    layer_new.height   = layer_new.print_z - layer_new.bottom_z;
+    return layer_new;
+}
+
+// Using the std::deque as an allocator.
+inline SupportGeneratorLayer& layer_allocate_unguarded(
+    SupportGeneratorLayerStorage      &layer_storage,
+    SupporLayerType                    layer_type,
+    const SlicingParameters           &slicing_params,
+    const TreeSupportSettings         &config, 
+    size_t                             layer_idx)
+{
+    SupportGeneratorLayer &layer = layer_storage.allocate_unguarded(layer_type);
+    return layer_initialize(layer, slicing_params, config, layer_idx);
+}
+
+inline SupportGeneratorLayer& layer_allocate(
+    SupportGeneratorLayerStorage      &layer_storage,
+    SupporLayerType                    layer_type,
+    const SlicingParameters           &slicing_params,
+    const TreeSupportSettings         &config, 
+    size_t                             layer_idx)
+{
+    SupportGeneratorLayer &layer = layer_storage.allocate(layer_type);
+    return layer_initialize(layer, slicing_params, config, layer_idx);
+}
+
+// Used by generate_initial_areas() in parallel by multiple layers.
+class InterfacePlacer {
+public:
+    InterfacePlacer(
+        const SlicingParameters         &slicing_parameters, 
+        const SupportParameters         &support_parameters,
+        const TreeSupportSettings       &config, 
+        SupportGeneratorLayerStorage    &layer_storage, 
+        SupportGeneratorLayersPtr       &top_contacts,
+        SupportGeneratorLayersPtr       &top_interfaces,
+        SupportGeneratorLayersPtr       &top_base_interfaces) 
+    :
+        slicing_parameters(slicing_parameters), support_parameters(support_parameters), config(config),
+        layer_storage(layer_storage), top_contacts(top_contacts), top_interfaces(top_interfaces), top_base_interfaces(top_base_interfaces)  
+    {}
+    InterfacePlacer(const InterfacePlacer& rhs) :
+        slicing_parameters(rhs.slicing_parameters), support_parameters(rhs.support_parameters), config(rhs.config),
+        layer_storage(rhs.layer_storage), top_contacts(rhs.top_contacts), top_interfaces(rhs.top_interfaces), top_base_interfaces(rhs.top_base_interfaces) 
+    {}
+
+    const SlicingParameters    &slicing_parameters;
+    const SupportParameters    &support_parameters;
+    const TreeSupportSettings  &config;
+    SupportGeneratorLayersPtr&  top_contacts_mutable() { return this->top_contacts; }
+
+public:
+    // Insert the contact layer and some of the inteface and base interface layers below.
+    void add_roofs(std::vector<Polygons> &&new_roofs, const size_t insert_layer_idx)
+    {
+        if (! new_roofs.empty()) {
+            std::lock_guard<std::mutex> lock(m_mutex_layer_storage);
+            for (size_t idx = 0; idx < new_roofs.size(); ++ idx)
+                if (! new_roofs[idx].empty())
+                    add_roof_unguarded(std::move(new_roofs[idx]), insert_layer_idx - idx, idx);
+        }
+    }
+
+    void add_roof(Polygons &&new_roof, const size_t insert_layer_idx, const size_t dtt_tip)
+    {
+        std::lock_guard<std::mutex> lock(m_mutex_layer_storage);
+        add_roof_unguarded(std::move(new_roof), insert_layer_idx, dtt_tip);
+    }
+
+    // called by sample_overhang_area()
+    void add_roof_build_plate(Polygons &&overhang_areas, size_t dtt_roof)
+    {
+        std::lock_guard<std::mutex> lock(m_mutex_layer_storage);
+        this->add_roof_unguarded(std::move(overhang_areas), 0, std::min(dtt_roof, this->support_parameters.num_top_interface_layers));
+    }
+
+    void add_roof_unguarded(Polygons &&new_roofs, const size_t insert_layer_idx, const size_t dtt_roof)
+    {
+        assert(support_parameters.has_top_contacts);
+        assert(dtt_roof <= support_parameters.num_top_interface_layers);
+        SupportGeneratorLayersPtr &layers =
+            dtt_roof == 0 ? this->top_contacts :
+            dtt_roof <= support_parameters.num_top_interface_layers_only() ? this->top_interfaces : this->top_base_interfaces;
+        SupportGeneratorLayer*& l = layers[insert_layer_idx];
+        if (l == nullptr)
+            l = &layer_allocate_unguarded(layer_storage, dtt_roof == 0 ? SupporLayerType::TopContact : SupporLayerType::TopInterface, 
+                    slicing_parameters, config, insert_layer_idx);
+        // will be unioned in finalize_interface_and_support_areas()
+        append(l->polygons, std::move(new_roofs));
+    }
+
+private:
+    // Outputs
+    SupportGeneratorLayerStorage                       &layer_storage;
+    SupportGeneratorLayersPtr                          &top_contacts;
+    SupportGeneratorLayersPtr                          &top_interfaces;
+    SupportGeneratorLayersPtr                          &top_base_interfaces;
+
+    // Mutexes, guards
+    std::mutex                                          m_mutex_layer_storage;
+};
+
+} // namespace FFFTreeSupport
+
+} // namespace Slic3r
+
+#endif // slic3r_TreeSupportCommon_hpp