Mesh: Add C++ implementaiton of topology mappings

Because they are friendlier to use in C++ code than the existing mesh
mapping API, these mappings from one domain to another were often
reimplemented in separate files. This commit moves some basic
implementations to a `mesh_topology` namespace in the existing
mesh mapping header file. These is plenty of room for performance
improvement here, particularly by not using an array of Vectors, but
that can come later.

Split from D16029

1 files changed, 20 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_mesh_mapping.h b/source/blender/blenkernel/BKE_mesh_mapping.h
index 2ee50fbaaee..350c4c4bb36 100644
--- a/source/blender/blenkernel/BKE_mesh_mapping.h
+++ b/source/blender/blenkernel/BKE_mesh_mapping.h
@@ -7,6 +7,10 @@
  */
 
 #ifdef __cplusplus
+#  include "BLI_array.hh"
+#endif
+
+#ifdef __cplusplus
 extern "C" {
 #endif
 
@@ -330,3 +334,19 @@ int *BKE_mesh_calc_smoothgroups(const struct MEdge *medge,
 #ifdef __cplusplus
 }
 #endif
+
+#ifdef __cplusplus
+namespace blender::mesh_topology {
+
+Array<int> build_corner_to_poly_map(Span<MPoly> polys, int loops_num);
+
+Array<Vector<int>> build_vert_to_edge_map(Span<MEdge> edges, int verts_num);
+Array<Vector<int>> build_vert_to_corner_map(Span<MLoop> loops, int verts_num);
+
+inline int previous_poly_corner(const MPoly &poly, int corner_i)
+{
+  return corner_i - 1 + (corner_i == poly.loopstart) * poly.totloop;
+}
+
+}  // namespace blender::mesh_topology
+#endif