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, 3 insertions, 2 deletions

diff --git a/source/blender/io/wavefront_obj/exporter/obj_export_file_writer.hh b/source/blender/io/wavefront_obj/exporter/obj_export_file_writer.hh
index 4544037fbc1..eda4576297b 100644
--- a/source/blender/io/wavefront_obj/exporter/obj_export_file_writer.hh
+++ b/source/blender/io/wavefront_obj/exporter/obj_export_file_writer.hh
@@ -186,7 +186,8 @@ class MTLWriter : NonMovable, NonCopyable {
    */
   void write_materials(const char *blen_filepath,
                        ePathReferenceMode path_mode,
-                       const char *dest_dir);
+                       const char *dest_dir,
+                       bool write_pbr);
   StringRefNull mtl_file_path() const;
   /**
    * Add the materials of the given object to #MTLWriter, de-duplicating
@@ -203,7 +204,7 @@ class MTLWriter : NonMovable, NonCopyable {
   /**
    * Write properties sourced from p-BSDF node or #Object.Material.
    */
-  void write_bsdf_properties(const MTLMaterial &mtl_material);
+  void write_bsdf_properties(const MTLMaterial &mtl_material, bool write_pbr);
   /**
    * Write a texture map in the form "map_XX -s 1. 1. 1. -o 0. 0. 0. [-bm 1.] path/to/image".
    */