Add parallel version of neighbors index creation, make it default

src/libslic3r/MeshSplitImpl.hpp

@@ -3,8 +3,13 @@
 
 #include "TriangleMesh.hpp"
 #include "libnest2d/tools/benchmark.h"
+#include "Execution/ExecutionTBB.hpp"
 
 namespace Slic3r {
+
+template<class ExPolicy>
+std::vector<Vec3i> create_neighbors_index(ExPolicy &&ex, const indexed_triangle_set &its);
+
 namespace meshsplit_detail {
 
 template<class Its, class Enable = void> struct ItsWithNeighborsIndex_ {
@@ -19,7 +24,7 @@ template<> struct ItsWithNeighborsIndex_<indexed_triangle_set> {
     static const indexed_triangle_set &get_its(const indexed_triangle_set &its) noexcept { return its; }
     static Index get_index(const indexed_triangle_set &its) noexcept
     {
-        return its_create_neighbors_index(its);
+        return create_neighbors_index(ex_tbb, its);
     }
 };
 
@@ -152,12 +157,68 @@ template<class Its> bool its_is_splittable(const Its &m)
     const auto& neighbor_index = ItsWithNeighborsIndex_<Its>::get_index(m);
 
     std::vector<char> visited(its.indices.size(), false);
-    its_find_unvisited_neighbors(its, neighbor_index, visited);
+    auto faces = its_find_unvisited_neighbors(its, neighbor_index, visited);
 
-    // Try finding an unvisited facet. If there are none, the mesh is not splittable.
-    auto it = std::find(visited.begin(), visited.end(), false);
+    return !faces.empty();
+}
 
-    return it != visited.end();
+inline int get_vertex_index(size_t vertex_index, const stl_triangle_vertex_indices &triangle_indices) {
+    if (int(vertex_index) == triangle_indices[0]) return 0;
+    if (int(vertex_index) == triangle_indices[1]) return 1;
+    if (int(vertex_index) == triangle_indices[2]) return 2;
+    return -1;
+}
+
+inline Vec2crd get_edge_indices(int edge_index, const stl_triangle_vertex_indices &triangle_indices)
+{
+    int next_edge_index = (edge_index == 2) ? 0 : edge_index + 1;
+    int vi0             = triangle_indices[edge_index];
+    int vi1             = triangle_indices[next_edge_index];
+    return Vec2crd(vi0, vi1);
+}
+
+template<class ExPolicy>
+std::vector<Vec3i> create_neighbors_index(ExPolicy &&ex, const indexed_triangle_set &its)
+{
+    const std::vector<stl_triangle_vertex_indices> &indices = its.indices;
+    size_t vertices_size = its.vertices.size();
+
+    if (indices.empty() || vertices_size == 0) return {};
+
+    auto               vertex_triangles = VertexFaceIndex{its};
+    constexpr int      no_value         = -1;
+    std::vector<Vec3i> neighbors(indices.size(),
+                                 Vec3i(no_value, no_value, no_value));
+
+    //for (const stl_triangle_vertex_indices& triangle_indices : indices) {
+    execution::for_each(ex, size_t(0), indices.size(),
+        [&neighbors, &indices, &vertex_triangles] (size_t index)
+        {
+            Vec3i& neighbor = neighbors[index];
+            const stl_triangle_vertex_indices & triangle_indices = indices[index];
+            for (int edge_index = 0; edge_index < 3; ++edge_index) {
+                // check if done
+                int& neighbor_edge = neighbor[edge_index];
+                if (neighbor_edge != no_value) continue;
+                Vec2crd edge_indices = get_edge_indices(edge_index, triangle_indices);
+                // IMPROVE: use same vector for 2 sides of triangle
+                const auto &faces_range = vertex_triangles[edge_indices[0]];
+                for (const size_t &face : faces_range) {
+                    if (face <= index) continue;
+                    const stl_triangle_vertex_indices &face_indices = indices[face];
+                    int vertex_index = get_vertex_index(edge_indices[1], face_indices);
+                    // NOT Contain second vertex?
+                    if (vertex_index < 0) continue;
+                    // Has NOT oposit direction?
+                    if (edge_indices[0] != face_indices[(vertex_index + 1) % 3]) continue;
+                    neighbor_edge = face;
+                    neighbors[face][vertex_index] = index;
+                    break;
+                }
+            }
+        }, execution::max_concurrency(ex));
+
+    return neighbors;
 }
 
 } // namespace Slic3r