Fix T98781: OBJ exporter wrongly writing default material socket values when textures are present

Report T98781 and part of T97642: the MTLMaterial info only captures
image nodes and the default socket values. When the image information
is present, do not emit the socket defaults - the .MTL spec states
they are multiplied together, but the default value is not used
in blender when the socket is connected.

Also contains svn tests repository update to extend the test coverage,
and update test expectation outputs.

1 files changed, 29 insertions, 18 deletions

diff --git a/source/blender/io/wavefront_obj/exporter/obj_export_file_writer.cc b/source/blender/io/wavefront_obj/exporter/obj_export_file_writer.cc
index 36a9cf1b9ae..53aa80700cc 100644
--- a/source/blender/io/wavefront_obj/exporter/obj_export_file_writer.cc
+++ b/source/blender/io/wavefront_obj/exporter/obj_export_file_writer.cc
@@ -547,20 +547,29 @@ StringRefNull MTLWriter::mtl_file_path() const
   return mtl_filepath_;
 }
 
-void MTLWriter::write_bsdf_properties(const MTLMaterial &mtl_material)
+void MTLWriter::write_bsdf_properties(const MTLMaterial &mtl)
 {
-  fmt_handler_.write<eMTLSyntaxElement::Ns>(mtl_material.Ns);
-  fmt_handler_.write<eMTLSyntaxElement::Ka>(
-      mtl_material.Ka.x, mtl_material.Ka.y, mtl_material.Ka.z);
-  fmt_handler_.write<eMTLSyntaxElement::Kd>(
-      mtl_material.Kd.x, mtl_material.Kd.y, mtl_material.Kd.z);
-  fmt_handler_.write<eMTLSyntaxElement::Ks>(
-      mtl_material.Ks.x, mtl_material.Ks.y, mtl_material.Ks.z);
-  fmt_handler_.write<eMTLSyntaxElement::Ke>(
-      mtl_material.Ke.x, mtl_material.Ke.y, mtl_material.Ke.z);
-  fmt_handler_.write<eMTLSyntaxElement::Ni>(mtl_material.Ni);
-  fmt_handler_.write<eMTLSyntaxElement::d>(mtl_material.d);
-  fmt_handler_.write<eMTLSyntaxElement::illum>(mtl_material.illum);
+  /* For various material properties, we only capture information
+   * coming from the texture, or the default value of the socket.
+   * When the texture is present, do not emit the default value. */
+  if (!mtl.tex_map_of_type(eMTLSyntaxElement::map_Ns).is_valid()) {
+    fmt_handler_.write<eMTLSyntaxElement::Ns>(mtl.Ns);
+  }
+  fmt_handler_.write<eMTLSyntaxElement::Ka>(mtl.Ka.x, mtl.Ka.y, mtl.Ka.z);
+  if (!mtl.tex_map_of_type(eMTLSyntaxElement::map_Kd).is_valid()) {
+    fmt_handler_.write<eMTLSyntaxElement::Kd>(mtl.Kd.x, mtl.Kd.y, mtl.Kd.z);
+  }
+  if (!mtl.tex_map_of_type(eMTLSyntaxElement::map_Ks).is_valid()) {
+    fmt_handler_.write<eMTLSyntaxElement::Ks>(mtl.Ks.x, mtl.Ks.y, mtl.Ks.z);
+  }
+  if (!mtl.tex_map_of_type(eMTLSyntaxElement::map_Ke).is_valid()) {
+    fmt_handler_.write<eMTLSyntaxElement::Ke>(mtl.Ke.x, mtl.Ke.y, mtl.Ke.z);
+  }
+  fmt_handler_.write<eMTLSyntaxElement::Ni>(mtl.Ni);
+  if (!mtl.tex_map_of_type(eMTLSyntaxElement::map_d).is_valid()) {
+    fmt_handler_.write<eMTLSyntaxElement::d>(mtl.d);
+  }
+  fmt_handler_.write<eMTLSyntaxElement::illum>(mtl.illum);
 }
 
 void MTLWriter::write_texture_map(
@@ -583,12 +592,13 @@ void MTLWriter::write_texture_map(
     options.append(" -bm ").append(std::to_string(mtl_material.map_Bump_strength));
   }
 
+  std::string path = path_reference(
+      texture_map.value.image_path.c_str(), blen_filedir, dest_dir, path_mode, &copy_set);
+  /* Always emit forward slashes for cross-platform compatibility. */
+  std::replace(path.begin(), path.end(), '\\', '/');
+
 #define SYNTAX_DISPATCH(eMTLSyntaxElement) \
   if (texture_map.key == eMTLSyntaxElement) { \
-    std::string path = path_reference( \
-        texture_map.value.image_path.c_str(), blen_filedir, dest_dir, path_mode, &copy_set); \
-    /* Always emit forward slashes for cross-platform compatibility. */ \
-    std::replace(path.begin(), path.end(), '\\', '/'); \
     fmt_handler_.write<eMTLSyntaxElement>(options, path.c_str()); \
     return; \
   }
@@ -600,6 +610,7 @@ void MTLWriter::write_texture_map(
   SYNTAX_DISPATCH(eMTLSyntaxElement::map_refl);
   SYNTAX_DISPATCH(eMTLSyntaxElement::map_Ke);
   SYNTAX_DISPATCH(eMTLSyntaxElement::map_Bump);
+#undef SYNTAX_DISPATCH
 
   BLI_assert(!"This map type was not written to the file.");
 }
@@ -626,7 +637,7 @@ void MTLWriter::write_materials(const char *blen_filepath,
     fmt_handler_.write<eMTLSyntaxElement::newmtl>(mtlmat.name);
     write_bsdf_properties(mtlmat);
     for (const auto &tex : mtlmat.texture_maps.items()) {
-      if (tex.value.image_path.empty()) {
+      if (!tex.value.is_valid()) {
         continue;
       }
       write_texture_map(mtlmat, tex, blen_filedir, dest_dir, path_mode, copy_set);