Merge branch 'blender-v3.1-release'

source/blender/bmesh/intern/bmesh_mesh_convert.cc

@@ -934,9 +934,9 @@ void BM_mesh_bm_to_me(Main *bmain, BMesh *bm, Mesh *me, const struct BMeshToMesh
   CustomData_add_layer(&me->ldata, CD_MLOOP, CD_ASSIGN, mloop, me->totloop);
   CustomData_add_layer(&me->pdata, CD_MPOLY, CD_ASSIGN, mpoly, me->totpoly);
 
-  /* There is no way to tell if BMesh normals are dirty or not. Instead of calculating the normals
-   * on the BMesh possibly unnecessarily, just tag them dirty on the resulting mesh. */
-  BKE_mesh_normals_tag_dirty(me);
+  /* Clear normals on the mesh completely, since the original vertex and polygon count might be
+   * different than the BMesh's. */
+  BKE_mesh_clear_derived_normals(me);
 
   me->cd_flag = BM_mesh_cd_flag_from_bmesh(bm);
 

source/blender/editors/mesh/meshtools.c

@@ -412,6 +412,7 @@ int ED_mesh_join_objects_exec(bContext *C, wmOperator *op)
    * Even though this mesh wont typically have run-time data, the Python API can for e.g.
    * create loop-triangle cache here, which is confusing when left in the mesh, see: T90798. */
   BKE_mesh_runtime_clear_geometry(me);
+  BKE_mesh_clear_derived_normals(me);
 
   /* new material indices and material array */
   if (totmat) {

source/blender/makesrna/intern/rna_mesh.c

@@ -456,6 +456,7 @@ static void rna_MeshPolygon_flip(ID *id, MPoly *mp)
   BKE_mesh_polygon_flip(mp, me->mloop, &me->ldata);
   BKE_mesh_tessface_clear(me);
   BKE_mesh_runtime_clear_geometry(me);
+  BKE_mesh_normals_tag_dirty(me);
 }
 
 static void rna_MeshLoopTriangle_verts_get(PointerRNA *ptr, int *values)

source/blender/makesrna/intern/rna_mesh_api.c

@@ -167,7 +167,7 @@ static void rna_Mesh_flip_normals(Mesh *mesh)
 {
   BKE_mesh_polygons_flip(mesh->mpoly, mesh->mloop, &mesh->ldata, mesh->totpoly);
   BKE_mesh_tessface_clear(mesh);
-  BKE_mesh_calc_normals(mesh);
+  BKE_mesh_normals_tag_dirty(mesh);
   BKE_mesh_runtime_clear_geometry(mesh);
 
   DEG_id_tag_update(&mesh->id, 0);