Fix T98874: new obj importer missing an option to import vertex groups

The old Python OBJ importer had a (somewhat confusingly named) "Keep
Vertex Order -> Poly Groups" option, that imported OBJ groups as
"vertex groups" on the resulting mesh. All vertices of any face were
assigned the vertex group, with a 1.0 weight.

The new C++ importer did not have this option. It was trying to do
something with vertex groups, but failing to actually achieve
anything :) -- the vertex groups were created on the wrong object
(later on overwritten by "nomain mesh to main mesh" operation);
vertex weights were set to 1.0/vertex_count, and each vertex was only
set to be in one group, even when it belongs to multiple faces from
different groups. End result was that to the user, vertex groups were
not visible/present at all (see T98874).

This patch adds the import option (named "Vertex Groups"), which is
off by default, and fixes the import code logic to actually do the
right thing. Tested on file from T98874; vertex groups are imported
just like with the Python importer.

Reviewed By: Howard Trickey
Differential Revision: https://developer.blender.org/D15200

1 files changed, 3 insertions, 3 deletions

diff --git a/source/blender/io/wavefront_obj/importer/obj_import_mesh.hh b/source/blender/io/wavefront_obj/importer/obj_import_mesh.hh
index 216717f3578..c6773cfa0cb 100644
--- a/source/blender/io/wavefront_obj/importer/obj_import_mesh.hh
+++ b/source/blender/io/wavefront_obj/importer/obj_import_mesh.hh
@@ -45,10 +45,9 @@ class MeshFromGeometry : NonMovable, NonCopyable {
   void fixup_invalid_faces();
   void create_vertices(Mesh *mesh);
   /**
-   * Create polygons for the Mesh, set smooth shading flags, deform group names,
-   * Materials.
+   * Create polygons for the Mesh, set smooth shading flags, Materials.
    */
-  void create_polys_loops(Object *obj, Mesh *mesh);
+  void create_polys_loops(Object *obj, Mesh *mesh, bool use_vertex_groups);
   /**
    * Add explicitly imported OBJ edges to the mesh.
    */
@@ -66,6 +65,7 @@ class MeshFromGeometry : NonMovable, NonCopyable {
                         Object *obj);
   void create_normals(Mesh *mesh);
   void create_colors(Mesh *mesh);
+  void create_vertex_groups(Object *obj);
 };
 
 }  // namespace blender::io::obj