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Improvements to support point generator

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- Separate the 3 bands -- dangling, sloping and full overhanging -- regions and handle them with different support force deficits.

- Use a heuristic for overhanging edges to increase the number of support points generated for them


- Try to make overhangs and slopes deficit depend on stable area.
This commit is contained in:
tamasmeszaros 2020-08-31 10:38:24 +02:00
parent a9a99de939
commit 26d5c30366
2 changed files with 143 additions and 52 deletions
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171
src/libslic3r/SLA/SupportPointGenerator.cpp
View file

@ -163,10 +163,10 @@ static std::vector<SupportPointGenerator::MyLayer> make_layers(
SupportPointGenerator::MyLayer &layer_below = layers[layer_id - 1];
//FIXME WTF?
const float layer_height = (layer_id!=0 ? heights[layer_id]-heights[layer_id-1] : heights[0]);
const float safe_angle = 5.f * (float(M_PI)/180.f); // smaller number - less supports
const float between_layers_offset = float(scale_(layer_height / std::tan(safe_angle)));
const float safe_angle = 35.f * (float(M_PI)/180.f); // smaller number - less supports
const float between_layers_offset = scaled<float>(layer_height * std::tan(safe_angle));
const float slope_angle = 75.f * (float(M_PI)/180.f); // smaller number - less supports
const float slope_offset = float(scale_(layer_height / std::tan(slope_angle)));
const float slope_offset = scaled<float>(layer_height * std::tan(slope_angle));
//FIXME This has a quadratic time complexity, it will be excessively slow for many tiny islands.
for (SupportPointGenerator::Structure &top : layer_above.islands) {
for (SupportPointGenerator::Structure &bottom : layer_below.islands) {
@ -181,6 +181,25 @@ static std::vector<SupportPointGenerator::MyLayer> make_layers(
Polygons bottom_polygons = top.polygons_below();
top.overhangs = diff_ex(top_polygons, bottom_polygons);
if (! top.overhangs.empty()) {
// Produce 2 bands around the island, a safe band for dangling overhangs
// and an unsafe band for sloped overhangs.
// These masks include the original island
auto dangl_mask = offset(bottom_polygons, between_layers_offset, ClipperLib::jtSquare);
auto overh_mask = offset(bottom_polygons, slope_offset, ClipperLib::jtSquare);
// Absolutely hopeless overhangs are those outside the unsafe band
top.overhangs = diff_ex(top_polygons, overh_mask);
// Now cut out the supported core from the safe band
// and cut the safe band from the unsafe band to get distinct
// zones.
overh_mask = diff(overh_mask, dangl_mask);
dangl_mask = diff(dangl_mask, bottom_polygons);
top.dangling_areas = intersection_ex(top_polygons, dangl_mask);
top.overhangs_slopes = intersection_ex(top_polygons, overh_mask);
top.overhangs_area = 0.f;
std::vector<std::pair<ExPolygon*, float>> expolys_with_areas;
for (ExPolygon &ex : top.overhangs) {
@ -196,8 +215,6 @@ static std::vector<SupportPointGenerator::MyLayer> make_layers(
overhangs_sorted.emplace_back(std::move(*p.first));
top.overhangs = std::move(overhangs_sorted);
top.overhangs_area *= float(SCALING_FACTOR * SCALING_FACTOR);
top.overhangs_slopes = diff_ex(top_polygons, offset(bottom_polygons, slope_offset));
top.dangling_areas = diff_ex(top_polygons, offset(bottom_polygons, between_layers_offset));
}
}
}
@ -256,21 +273,9 @@ void SupportPointGenerator::process(const std::vector<ExPolygons>& slices, const
// Now iterate over all polygons and append new points if needed.
for (Structure &s : layer_top->islands) {
// Penalization resulting from large diff from the last layer:
// s.supports_force_inherited /= std::max(1.f, (layer_height / 0.3f) * e_area / s.area);
s.supports_force_inherited /= std::max(1.f, 0.17f * (s.overhangs_area) / s.area);
//float force_deficit = s.support_force_deficit(m_config.tear_pressure());
if (s.islands_below.empty()) { // completely new island - needs support no doubt
uniformly_cover({ *s.polygon }, s, point_grid, true);
} else if (! s.dangling_areas.empty()) {
// Let's see if there's anything that overlaps enough to need supports:
// What we now have in polygons needs support, regardless of what the forces are, so we can add them.
//FIXME is it an island point or not? Vojtech thinks it is.
uniformly_cover(s.dangling_areas, s, point_grid);
} else if (! s.overhangs_slopes.empty()) {
//FIXME add the support force deficit as a parameter, only cover until the defficiency is covered.
uniformly_cover(s.overhangs_slopes, s, point_grid);
}
add_support_points(s, point_grid);
}
m_throw_on_cancel();
@ -288,6 +293,42 @@ void SupportPointGenerator::process(const std::vector<ExPolygons>& slices, const
}
}
void SupportPointGenerator::add_support_points(SupportPointGenerator::Structure &s, SupportPointGenerator::PointGrid3D &grid3d)
{
// Select each type of surface (overrhang, dangling, slope), derive the support
// force deficit for it and call uniformly conver with the right params
float tp = m_config.tear_pressure();
float current = s.supports_force_total();
static constexpr float SLOPE_DAMPING = .0015f;
static constexpr float DANGL_DAMPING = .09f;
if (s.islands_below.empty()) {
// completely new island - needs support no doubt
// deficit is full, there is nothing below that would hold this island
uniformly_cover({ *s.polygon }, s, s.area * tp, grid3d, IslandCoverageFlags(icfIsNew | icfBoundaryOnly) );
return;
}
auto areafn = [](double sum, auto &p) { return sum + p.area() * SCALING_FACTOR * SCALING_FACTOR; };
if (! s.dangling_areas.empty()) {
// Let's see if there's anything that overlaps enough to need supports:
// What we now have in polygons needs support, regardless of what the forces are, so we can add them.
double a = std::accumulate(s.dangling_areas.begin(), s.dangling_areas.end(), 0., areafn);
uniformly_cover(s.dangling_areas, s, a * tp - current * DANGL_DAMPING * std::sqrt(1. - a / s.area), grid3d);
}
if (! s.overhangs_slopes.empty()) {
double a = std::accumulate(s.overhangs_slopes.begin(), s.overhangs_slopes.end(), 0., areafn);
uniformly_cover(s.overhangs_slopes, s, a * tp - current * SLOPE_DAMPING * std::sqrt(1. - a / s.area), grid3d);
}
if (! s.overhangs.empty()) {
uniformly_cover(s.overhangs, s, s.overhangs_area * tp, grid3d);
}
}
std::vector<Vec2f> sample_expolygon(const ExPolygon &expoly, float samples_per_mm2, std::mt19937 &rng)
{
// Triangulate the polygon with holes into triplets of 3D points.
@ -297,16 +338,16 @@ std::vector<Vec2f> sample_expolygon(const ExPolygon &expoly, float samples_per_m
if (! triangles.empty())
{
// Calculate area of each triangle.
std::vector<float> areas;
areas.reserve(triangles.size() / 3);
auto areas = reserve_vector<float>(triangles.size() / 3);
double aback = 0.;
for (size_t i = 0; i < triangles.size(); ) {
const Vec2f &a = triangles[i ++];
const Vec2f v1 = triangles[i ++] - a;
const Vec2f v2 = triangles[i ++] - a;
areas.emplace_back(0.5f * std::abs(cross2(v1, v2)));
if (i != 3)
// Prefix sum of the areas.
areas.back() += areas[areas.size() - 2];
// Prefix sum of the areas.
areas.emplace_back(aback + 0.5f * std::abs(cross2(v1, v2)));
aback = areas.back();
}
size_t num_samples = size_t(ceil(areas.back() * samples_per_mm2));
@ -316,7 +357,7 @@ std::vector<Vec2f> sample_expolygon(const ExPolygon &expoly, float samples_per_m
double r = random_triangle(rng);
size_t idx_triangle = std::min<size_t>(std::upper_bound(areas.begin(), areas.end(), (float)r) - areas.begin(), areas.size() - 1) * 3;
// Select a random point on the triangle.
double u = float(sqrt(random_float(rng)));
double u = float(std::sqrt(random_float(rng)));
double v = float(random_float(rng));
const Vec2f &a = triangles[idx_triangle ++];
const Vec2f &b = triangles[idx_triangle++];
@ -328,16 +369,37 @@ std::vector<Vec2f> sample_expolygon(const ExPolygon &expoly, float samples_per_m
return out;
}
std::vector<Vec2f> sample_expolygon(const ExPolygons &expolys, float samples_per_mm2, std::mt19937 &rng)
{
std::vector<Vec2f> out;
for (const ExPolygon &expoly : expolys)
append(out, sample_expolygon(expoly, samples_per_mm2, rng));
return out;
}
void sample_expolygon_boundary(const ExPolygon & expoly,
float samples_per_mm,
std::vector<Vec2f> &out,
std::mt19937 & rng)
{
double point_stepping_scaled = scale_(1.f) / samples_per_mm;
for (size_t i_contour = 0; i_contour <= expoly.holes.size(); ++ i_contour) {
const Polygon &contour = (i_contour == 0) ? expoly.contour :
expoly.holes[i_contour - 1];
const Points pts = contour.equally_spaced_points(point_stepping_scaled);
for (size_t i = 0; i < pts.size(); ++ i)
out.emplace_back(unscale<float>(pts[i].x()),
unscale<float>(pts[i].y()));
}
}
std::vector<Vec2f> sample_expolygon_with_boundary(const ExPolygon &expoly, float samples_per_mm2, float samples_per_mm_boundary, std::mt19937 &rng)
{
std::vector<Vec2f> out = sample_expolygon(expoly, samples_per_mm2, rng);
double point_stepping_scaled = scale_(1.f) / samples_per_mm_boundary;
for (size_t i_contour = 0; i_contour <= expoly.holes.size(); ++ i_contour) {
const Polygon &contour = (i_contour == 0) ? expoly.contour : expoly.holes[i_contour - 1];
const Points pts = contour.equally_spaced_points(point_stepping_scaled);
for (size_t i = 0; i < pts.size(); ++ i)
out.emplace_back(unscale<float>(pts[i].x()), unscale<float>(pts[i].y()));
}
sample_expolygon_boundary(expoly, samples_per_mm_boundary, out, rng);
return out;
}
@ -359,17 +421,17 @@ static inline std::vector<Vec2f> poisson_disk_from_samples(const std::vector<Vec
}
// Assign the raw samples to grid cells, sort the grid cells lexicographically.
struct RawSample {
struct RawSample
{
Vec2f coord;
Vec2i cell_id;
RawSample(const Vec2f &crd = {}, const Vec2i &id = {}): coord{crd}, cell_id{id} {}
};
std::vector<RawSample> raw_samples_sorted;
RawSample sample;
for (const Vec2f &pt : raw_samples) {
sample.coord = pt;
sample.cell_id = ((pt - corner_min) / radius).cast<int>();
raw_samples_sorted.emplace_back(sample);
}
auto raw_samples_sorted = reserve_vector<RawSample>(raw_samples.size());
for (const Vec2f &pt : raw_samples)
raw_samples_sorted.emplace_back(pt, ((pt - corner_min) / radius).cast<int>());
std::sort(raw_samples_sorted.begin(), raw_samples_sorted.end(), [](const RawSample &lhs, const RawSample &rhs)
{ return lhs.cell_id.x() < rhs.cell_id.x() || (lhs.cell_id.x() == rhs.cell_id.x() && lhs.cell_id.y() < rhs.cell_id.y()); });
@ -464,11 +526,22 @@ static inline std::vector<Vec2f> poisson_disk_from_samples(const std::vector<Vec
return out;
}
void SupportPointGenerator::uniformly_cover(const ExPolygons& islands, Structure& structure, PointGrid3D &grid3d, bool is_new_island, bool just_one)
void SupportPointGenerator::uniformly_cover(const ExPolygons& islands, Structure& structure, float deficit, PointGrid3D &grid3d, IslandCoverageFlags flags)
{
//int num_of_points = std::max(1, (int)((island.area()*pow(SCALING_FACTOR, 2) * m_config.tear_pressure)/m_config.support_force));
const float support_force_deficit = structure.support_force_deficit(m_config.tear_pressure());
float support_force_deficit = deficit;
auto bb = get_extents(islands);
if (flags & icfIsNew) {
Vec2d bbdim = unscaled(Vec2crd{bb.max - bb.min});
if (bbdim.x() > bbdim.y()) std::swap(bbdim.x(), bbdim.y());
double aspectr = bbdim.y() / bbdim.x();
support_force_deficit *= (1 + aspectr / 2.);
}
if (support_force_deficit < 0)
return;
@ -485,13 +558,18 @@ void SupportPointGenerator::uniformly_cover(const ExPolygons& islands, Structure
float min_spacing = poisson_radius;
//FIXME share the random generator. The random generator may be not so cheap to initialize, also we don't want the random generator to be restarted for each polygon.
std::vector<Vec2f> raw_samples = sample_expolygon_with_boundary(islands, samples_per_mm2, 5.f / poisson_radius, m_rng);
std::vector<Vec2f> raw_samples =
flags & icfBoundaryOnly ?
sample_expolygon_with_boundary(islands, samples_per_mm2,
5.f / poisson_radius, m_rng) :
sample_expolygon(islands, samples_per_mm2, m_rng);
std::vector<Vec2f> poisson_samples;
for (size_t iter = 0; iter < 4; ++ iter) {
poisson_samples = poisson_disk_from_samples(raw_samples, poisson_radius,
[&structure, &grid3d, min_spacing](const Vec2f &pos) {
return grid3d.collides_with(pos, &structure, min_spacing);
return grid3d.collides_with(pos, structure.layer->print_z, min_spacing);
});
if (poisson_samples.size() >= poisson_samples_target || m_config.minimal_distance > poisson_radius-EPSILON)
break;
@ -521,12 +599,13 @@ void SupportPointGenerator::uniformly_cover(const ExPolygons& islands, Structure
poisson_samples.erase(poisson_samples.begin() + poisson_samples_target, poisson_samples.end());
}
for (const Vec2f &pt : poisson_samples) {
m_output.emplace_back(float(pt(0)), float(pt(1)), structure.height, m_config.head_diameter/2.f, is_new_island);
m_output.emplace_back(float(pt(0)), float(pt(1)), structure.zlevel, m_config.head_diameter/2.f, flags & icfIsNew);
structure.supports_force_this_layer += m_config.support_force();
grid3d.insert(pt, &structure);
}
}
void remove_bottom_points(std::vector<SupportPoint> &pts, float lvl)
{
// get iterator to the reorganized vector end

24
src/libslic3r/SLA/SupportPointGenerator.hpp
View file

@ -38,8 +38,8 @@ public:
struct MyLayer;
struct Structure {
Structure(MyLayer &layer, const ExPolygon& poly, const BoundingBox &bbox, const Vec2f &centroid, float area, float h) :
layer(&layer), polygon(&poly), bbox(bbox), centroid(centroid), area(area), height(h)
Structure(MyLayer &layer, const ExPolygon& poly, const BoundingBox &bbox, const Vec2f &centroid, float area, float h) :
layer(&layer), polygon(&poly), bbox(bbox), centroid(centroid), area(area), zlevel(h)
#ifdef SLA_SUPPORTPOINTGEN_DEBUG
, unique_id(std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::system_clock::now().time_since_epoch()))
#endif /* SLA_SUPPORTPOINTGEN_DEBUG */
@ -49,7 +49,7 @@ public:
const BoundingBox bbox;
const Vec2f centroid = Vec2f::Zero();
const float area = 0.f;
float height = 0;
float zlevel = 0;
// How well is this ExPolygon held to the print base?
// Positive number, the higher the better.
float supports_force_this_layer = 0.f;
@ -159,8 +159,8 @@ public:
grid.emplace(cell_id(pt.position), pt);
}
bool collides_with(const Vec2f &pos, Structure *island, float radius) {
Vec3f pos3d(pos.x(), pos.y(), float(island->layer->print_z));
bool collides_with(const Vec2f &pos, float print_z, float radius) {
Vec3f pos3d(pos.x(), pos.y(), print_z);
Vec3i cell = cell_id(pos3d);
std::pair<Grid::const_iterator, Grid::const_iterator> it_pair = grid.equal_range(cell);
if (collides_with(pos3d, radius, it_pair.first, it_pair.second))
@ -198,7 +198,16 @@ private:
SupportPointGenerator::Config m_config;
void process(const std::vector<ExPolygons>& slices, const std::vector<float>& heights);
void uniformly_cover(const ExPolygons& islands, Structure& structure, PointGrid3D &grid3d, bool is_new_island = false, bool just_one = false);
public:
enum IslandCoverageFlags : uint8_t { icfNone = 0x0, icfIsNew = 0x1, icfBoundaryOnly = 0x2 };
private:
void uniformly_cover(const ExPolygons& islands, Structure& structure, float deficit, PointGrid3D &grid3d, IslandCoverageFlags flags = icfNone);
void add_support_points(Structure& structure, PointGrid3D &grid3d);
void project_onto_mesh(std::vector<SupportPoint>& points) const;
#ifdef SLA_SUPPORTPOINTGEN_DEBUG
@ -215,6 +224,9 @@ private:
void remove_bottom_points(std::vector<SupportPoint> &pts, float lvl);
std::vector<Vec2f> sample_expolygon(const ExPolygon &expoly, float samples_per_mm2, std::mt19937 &rng);
void sample_expolygon_boundary(const ExPolygon &expoly, float samples_per_mm, std::vector<Vec2f> &out, std::mt19937 &rng);
}} // namespace Slic3r::sla
#endif // SUPPORTPOINTGENERATOR_HPP