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, 7 insertions, 0 deletions

diff --git a/source/blender/editors/io/io_obj.c b/source/blender/editors/io/io_obj.c
index f1cd7607771..bb3b1a43ba5 100644
--- a/source/blender/editors/io/io_obj.c
+++ b/source/blender/editors/io/io_obj.c
@@ -408,6 +408,7 @@ static int wm_obj_import_exec(bContext *C, wmOperator *op)
   import_params.clamp_size = RNA_float_get(op->ptr, "clamp_size");
   import_params.forward_axis = RNA_enum_get(op->ptr, "forward_axis");
   import_params.up_axis = RNA_enum_get(op->ptr, "up_axis");
+  import_params.import_vertex_groups = RNA_boolean_get(op->ptr, "import_vertex_groups");
   import_params.validate_meshes = RNA_boolean_get(op->ptr, "validate_meshes");
 
   OBJ_import(C, &import_params);
@@ -438,6 +439,7 @@ static void ui_obj_import_settings(uiLayout *layout, PointerRNA *imfptr)
   box = uiLayoutBox(layout);
   uiItemL(box, IFACE_("Options"), ICON_EXPORT);
   col = uiLayoutColumn(box, false);
+  uiItemR(col, imfptr, "import_vertex_groups", 0, NULL, ICON_NONE);
   uiItemR(col, imfptr, "validate_meshes", 0, NULL, ICON_NONE);
 }
 
@@ -487,6 +489,11 @@ void WM_OT_obj_import(struct wmOperatorType *ot)
                "");
   RNA_def_enum(ot->srna, "up_axis", io_obj_transform_axis_up, OBJ_AXIS_Y_UP, "Up Axis", "");
   RNA_def_boolean(ot->srna,
+                  "import_vertex_groups",
+                  false,
+                  "Vertex Groups",
+                  "Import OBJ groups as vertex groups");
+  RNA_def_boolean(ot->srna,
                   "validate_meshes",
                   false,
                   "Validate Meshes",