Fix T96430: new OBJ exporter wrong normals for non-uniform scale, and wrong face order for negative scale

This applies patch D14343 from Aras Pranckevicius, with a description:

The new 3.1+ OBJ exporter did not have correct logic when faced with
non-uniform & mirrored (negative on odd number of axes) object scale:

- Normals were not transformed correctly (should use inverse transpose of the matrix),
 and were not normalized,
- Face order was not "flipped" when transform has negative scale on odd number of axes
 (visible when using "face orientation" viewport overlay).

1 files changed, 10 insertions, 0 deletions

diff --git a/source/blender/io/wavefront_obj/tests/obj_exporter_tests.cc b/source/blender/io/wavefront_obj/tests/obj_exporter_tests.cc
index cc1cca74a38..27f34ca6be9 100644
--- a/source/blender/io/wavefront_obj/tests/obj_exporter_tests.cc
+++ b/source/blender/io/wavefront_obj/tests/obj_exporter_tests.cc
@@ -405,6 +405,16 @@ TEST_F(obj_exporter_regression_test, vertices)
       "io_tests/blend_geometry/vertices.blend", "io_tests/obj/vertices.obj", "", _export.params);
 }
 
+TEST_F(obj_exporter_regression_test, non_uniform_scale)
+{
+  OBJExportParamsDefault _export;
+  _export.params.export_materials = false;
+  compare_obj_export_to_golden("io_tests/blend_geometry/non_uniform_scale.blend",
+                               "io_tests/obj/non_uniform_scale.obj",
+                               "",
+                               _export.params);
+}
+
 TEST_F(obj_exporter_regression_test, nurbs_as_nurbs)
 {
   OBJExportParamsDefault _export;