obj: implement support for PBR .mtl extensions

Implement import & export support for "PBR extensions" in .mtl files
(T101029, also fixes T86736).

Newly supported parameters:
- Roughness (Pr, map_Pr)
- Metallic (Pm, map_Pm)
- Sheen (Ps, map_Ps)
- Clearcoat thickness (Pc) and roughness (Pcr)
- Anisotropy (aniso) and rotation (anisor)
- Transmittance (Tf / Kt)

Exporter has an option to enable these additional PBR parameters
export; defaults to off since not all software understands that.

Exporter UI tweaked and all material-related options were put into
their own separate box.

Added/extended test files in Subversion repository for test coverage.

1 files changed, 23 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 0fd711bdac6..dcba78ac99e 100644
--- a/source/blender/io/wavefront_obj/tests/obj_exporter_tests.cc
+++ b/source/blender/io/wavefront_obj/tests/obj_exporter_tests.cc
@@ -527,4 +527,27 @@ TEST_F(obj_exporter_regression_test, all_objects_mat_groups)
                                _export.params);
 }
 
+TEST_F(obj_exporter_regression_test, materials_without_pbr)
+{
+  OBJExportParamsDefault _export;
+  _export.params.export_normals = false;
+  _export.params.path_mode = PATH_REFERENCE_RELATIVE;
+  compare_obj_export_to_golden("io_tests/blend_geometry/materials_pbr.blend",
+                               "io_tests/obj/materials_without_pbr.obj",
+                               "io_tests/obj/materials_without_pbr.mtl",
+                               _export.params);
+}
+
+TEST_F(obj_exporter_regression_test, materials_pbr)
+{
+  OBJExportParamsDefault _export;
+  _export.params.export_normals = false;
+  _export.params.path_mode = PATH_REFERENCE_RELATIVE;
+  _export.params.export_pbr_extensions = true;
+  compare_obj_export_to_golden("io_tests/blend_geometry/materials_pbr.blend",
+                               "io_tests/obj/materials_pbr.obj",
+                               "io_tests/obj/materials_pbr.mtl",
+                               _export.params);
+}
+
 }  // namespace blender::io::obj