Fix T100421: OBJ importer in 3.3 does not keep the vertex order

While fixing T100302 (rBd76583cb4a1) I did not realize that the
change in imported vertex order would actually matter. Turns out, it
does for morph targets / mesh shape keys. So redo the fix in a way
that does not change the vertex order. Fixes T100421.

2 files changed, 20 insertions, 18 deletions

diff --git a/source/blender/io/wavefront_obj/importer/obj_import_mesh.cc b/source/blender/io/wavefront_obj/importer/obj_import_mesh.cc
index e62470588ec..a570b374231 100644
--- a/source/blender/io/wavefront_obj/importer/obj_import_mesh.cc
+++ b/source/blender/io/wavefront_obj/importer/obj_import_mesh.cc
@@ -157,17 +157,21 @@ void MeshFromGeometry::fixup_invalid_faces()
 
 void MeshFromGeometry::create_vertices(Mesh *mesh)
 {
-  int mi = 0;
-  for (int vi : mesh_geometry_.vertices_) {
-    if (vi < global_vertices_.vertices.size()) {
-      copy_v3_v3(mesh->mvert[mi].co, global_vertices_.vertices[vi]);
-    }
-    else {
-      std::cerr << "Vertex index:" << vi
-                << " larger than total vertices:" << global_vertices_.vertices.size() << " ."
-                << std::endl;
+  /* Go through all the global vertex indices from min to max,
+   * checking which ones are actually and building a global->local
+   * index mapping. Write out the used vertex positions into the Mesh
+   * data. */
+  mesh_geometry_.global_to_local_vertices_.clear();
+  mesh_geometry_.global_to_local_vertices_.reserve(mesh_geometry_.vertices_.size());
+  for (int vi = mesh_geometry_.vertex_index_min_; vi <= mesh_geometry_.vertex_index_max_; ++vi) {
+    BLI_assert(vi >= 0 && vi < global_vertices_.vertices.size());
+    if (!mesh_geometry_.vertices_.contains(vi)) {
+      continue;
     }
-    ++mi;
+    int local_vi = (int)mesh_geometry_.global_to_local_vertices_.size();
+    BLI_assert(local_vi >= 0 && local_vi < mesh->totvert);
+    copy_v3_v3(mesh->mvert[local_vi].co, global_vertices_.vertices[vi]);
+    mesh_geometry_.global_to_local_vertices_.add_new(vi, local_vi);
   }
 }
 
diff --git a/source/blender/io/wavefront_obj/importer/obj_import_objects.hh b/source/blender/io/wavefront_obj/importer/obj_import_objects.hh
index f48b6dd55e8..04d9a665588 100644
--- a/source/blender/io/wavefront_obj/importer/obj_import_objects.hh
+++ b/source/blender/io/wavefront_obj/importer/obj_import_objects.hh
@@ -11,8 +11,8 @@
 #include "BLI_map.hh"
 #include "BLI_math_base.hh"
 #include "BLI_math_vec_types.hh"
+#include "BLI_set.hh"
 #include "BLI_vector.hh"
-#include "BLI_vector_set.hh"
 
 #include "DNA_meshdata_types.h"
 #include "DNA_object_types.h"
@@ -93,9 +93,11 @@ struct Geometry {
 
   int vertex_index_min_ = INT_MAX;
   int vertex_index_max_ = -1;
-  VectorSet<int> vertices_;
+  /* Global vertex indices used by this geometry. */
+  Set<int> vertices_;
+  /* Mapping from global vertex index to geometry-local vertex index. */
   Map<int, int> global_to_local_vertices_;
-  /** Edges written in the file in addition to (or even without polygon) elements. */
+  /* Loose edges in the file. */
   Vector<MEdge> edges_;
 
   Vector<PolyCorner> face_corners_;
@@ -112,19 +114,15 @@ struct Geometry {
   }
   void track_vertex_index(int index)
   {
-    if (vertices_.add(index)) {
-      global_to_local_vertices_.add_new(index, (int)vertices_.size() - 1);
-    }
+    vertices_.add(index);
     math::min_inplace(vertex_index_min_, index);
     math::max_inplace(vertex_index_max_, index);
   }
   void track_all_vertices(int count)
   {
     vertices_.reserve(count);
-    global_to_local_vertices_.reserve(count);
     for (int i = 0; i < count; ++i) {
       vertices_.add(i);
-      global_to_local_vertices_.add(i, i);
     }
     vertex_index_min_ = 0;
     vertex_index_max_ = count - 1;