FBX: Add material name collision mode

Introduces the Material Name Collision option, similar to how
USD / OBJ importers have it.

Pull Request: https://projects.blender.org/blender/blender/pulls/144375

scripts/addons_core/io_scene_fbx/__init__.py

@@ -198,6 +198,15 @@ class ImportFBX(bpy.types.Operator, ImportHelper):
         description="Use pre/post rotation from FBX transform (you may have to disable that in some cases)",
         default=True,
     )
+    mtl_name_collision_mode: EnumProperty(
+        name="Material Name Collision",
+        items=(("MAKE_UNIQUE", "Make Unique", "Import each FBX material as a unique Blender material"),
+               ("REFERENCE_EXISTING", "Reference Existing",
+               "If a material with the same name already exists, reference that instead of importing"),
+               ),
+        default='MAKE_UNIQUE',
+        description="Behavior when the name of an imported material conflicts with an existing material",
+    )
 
     def draw(self, context):
         layout = self.layout
@@ -206,6 +215,7 @@ class ImportFBX(bpy.types.Operator, ImportHelper):
 
         import_panel_include(layout, self)
         import_panel_transform(layout, self)
+        import_panel_materials(layout, self)
         import_panel_animation(layout, self)
         import_panel_armature(layout, self)
 
@@ -267,6 +277,11 @@ def import_panel_transform_orientation(layout, operator):
         body.prop(operator, "axis_forward")
         body.prop(operator, "axis_up")
 
+def import_panel_materials(layout, operator):
+    header, body = layout.panel("FBX_import_material", default_closed=True)
+    header.label(text="Materials")
+    if body:
+        body.prop(operator, "mtl_name_collision_mode")
 
 def import_panel_animation(layout, operator):
     header, body = layout.panel("FBX_import_animation", default_closed=True)
@@ -290,7 +305,6 @@ def import_panel_armature(layout, operator):
         sub.prop(operator, "primary_bone_axis")
         sub.prop(operator, "secondary_bone_axis")
 
-
 @orientation_helper(axis_forward='-Z', axis_up='Y')
 class ExportFBX(bpy.types.Operator, ExportHelper):
     """Write a FBX file"""

scripts/addons_core/io_scene_fbx/fbx_utils.py

@@ -1927,5 +1927,5 @@ FBXImportSettings = namedtuple("FBXImportSettings", (
     "use_custom_props", "use_custom_props_enum_as_string",
     "nodal_material_wrap_map", "image_cache",
     "ignore_leaf_bones", "force_connect_children", "automatic_bone_orientation", "bone_correction_matrix",
-    "use_prepost_rot", "colors_type",
+    "use_prepost_rot", "colors_type", "mtl_name_collision_mode",
 ))

scripts/addons_core/io_scene_fbx/import_fbx.py

@@ -2050,6 +2050,10 @@ def blen_read_material(fbx_tmpl, fbx_obj, settings):
 
     elem_name_utf8 = elem_name_ensure_class(fbx_obj, b'Material')
 
+    if settings.mtl_name_collision_mode == "REFERENCE_EXISTING":
+        if (ma := bpy.data.materials.get(elem_name_utf8)):
+            return ma
+
     nodal_material_wrap_map = settings.nodal_material_wrap_map
     ma = bpy.data.materials.new(name=elem_name_utf8)
 
@@ -3043,7 +3047,8 @@ def load(operator, context, filepath="",
          primary_bone_axis='Y',
          secondary_bone_axis='X',
          use_prepost_rot=True,
-         colors_type='SRGB'):
+         colors_type='SRGB',
+         mtl_name_collision_mode="MAKE_UNIQUE"):
 
     global fbx_elem_nil
     fbx_elem_nil = FBXElem('', (), (), ())
@@ -3182,7 +3187,7 @@ def load(operator, context, filepath="",
         use_custom_props, use_custom_props_enum_as_string,
         nodal_material_wrap_map, image_cache,
         ignore_leaf_bones, force_connect_children, automatic_bone_orientation, bone_correction_matrix,
-        use_prepost_rot, colors_type,
+        use_prepost_rot, colors_type, mtl_name_collision_mode,
     )
 
     # #### And now, the "real" data.

source/blender/editors/io/io_fbx_ops.cc

@@ -33,6 +33,20 @@
 #  include "io_fbx_ops.hh"
 #  include "io_utils.hh"
 
+const EnumPropertyItem rna_enum_fbx_mtl_name_collision_mode_items[] = {
+    {int(eFBXMtlNameCollisionMode::MakeUnique),
+     "MAKE_UNIQUE",
+     0,
+     "Make Unique",
+     "Import each FBX material as a unique Blender material"},
+    {int(eFBXMtlNameCollisionMode::ReferenceExisting),
+     "REFERENCE_EXISTING",
+     0,
+     "Reference Existing",
+     "If a material with the same name already exists, reference that instead of importing"},
+    {0, nullptr, 0, nullptr, nullptr},
+};
+
 static const EnumPropertyItem fbx_vertex_colors_mode[] = {
     {int(eFBXVertexColorMode::None), "NONE", 0, "None", "Do not import color attributes"},
     {int(eFBXVertexColorMode::sRGB),
@@ -60,6 +74,8 @@ static wmOperatorStatus wm_fbx_import_exec(bContext *C, wmOperator *op)
   params.use_anim = RNA_boolean_get(op->ptr, "use_anim");
   params.anim_offset = RNA_float_get(op->ptr, "anim_offset");
   params.vertex_colors = eFBXVertexColorMode(RNA_enum_get(op->ptr, "import_colors"));
+  params.mtl_name_collision_mode = eFBXMtlNameCollisionMode(
+      RNA_enum_get(op->ptr, "mtl_name_collision_mode"));
 
   params.reports = op->reports;
 
@@ -110,6 +126,11 @@ static void ui_fbx_import_settings(const bContext *C, uiLayout *layout, PointerR
     col->prop(ptr, "validate_meshes", UI_ITEM_NONE, std::nullopt, ICON_NONE);
   }
 
+  if (uiLayout *panel = layout->panel(C, "FBX_import_material", true, IFACE_("Materials"))) {
+    uiLayout *col = &panel->column(false);
+    col->prop(ptr, "mtl_name_collision_mode", UI_ITEM_NONE, std::nullopt, ICON_NONE);
+  }
+
   {
     PanelLayout panel = layout->panel(C, "FBX_import_anim", true);
     panel.header->use_property_split_set(false);
@@ -157,6 +178,14 @@ void WM_OT_fbx_import(wmOperatorType *ot)
                                  FILE_SORT_DEFAULT);
 
   RNA_def_float(ot->srna, "global_scale", 1.0f, 1e-6f, 1e6f, "Scale", "", 0.001f, 1000.0f);
+
+  RNA_def_enum(
+      ot->srna,
+      "mtl_name_collision_mode",
+      rna_enum_fbx_mtl_name_collision_mode_items,
+      int(eFBXMtlNameCollisionMode::MakeUnique),
+      "Material Name Collision",
+      "Behavior when the name of an imported material conflicts with an existing material");
   RNA_def_enum(ot->srna,
                "import_colors",
                fbx_vertex_colors_mode,

source/blender/io/fbx/IO_fbx.hh

@@ -18,6 +18,15 @@ struct Mesh;
 struct bContext;
 struct ReportList;
 
+/**
+ * Behavior when the name of an imported material
+ * conflicts with an existing material.
+ */
+enum class eFBXMtlNameCollisionMode {
+  MakeUnique = 0,
+  ReferenceExisting = 1,
+};
+
 enum class eFBXVertexColorMode {
   None = 0,
   sRGB = 1,
@@ -27,6 +36,7 @@ enum class eFBXVertexColorMode {
 struct FBXImportParams {
   char filepath[FILE_MAX] = "";
   float global_scale = 1.0f;
+  eFBXMtlNameCollisionMode mtl_name_collision_mode = eFBXMtlNameCollisionMode::MakeUnique;
   eFBXVertexColorMode vertex_colors = eFBXVertexColorMode::sRGB;
   bool validate_meshes = true;
   bool use_custom_normals = true;

source/blender/io/fbx/importer/fbx_import.cc

@@ -8,6 +8,7 @@
 
 #include "BKE_camera.h"
 #include "BKE_layer.hh"
+#include "BKE_lib_id.hh"
 #include "BKE_light.h"
 #include "BKE_object.hh"
 #include "BKE_report.hh"
@@ -98,9 +99,17 @@ void FbxImportContext::import_globals(Scene *scene) const
 void FbxImportContext::import_materials()
 {
   for (const ufbx_material *fmat : this->fbx.materials) {
-    Material *mat = io::fbx::import_material(this->bmain, this->base_dir, *fmat);
-    if (this->params.use_custom_props) {
-      read_custom_properties(fmat->props, mat->id, this->params.props_enum_as_string);
+    Material *mat = nullptr;
+    /* Check if a material with this name already exists in the main database */
+    if (this->params.mtl_name_collision_mode == eFBXMtlNameCollisionMode::ReferenceExisting) {
+      mat = (Material *)BKE_libblock_find_name(this->bmain, ID_MA, fmat->name.data);
+    }
+
+    if (mat == nullptr) {
+      mat = io::fbx::import_material(this->bmain, this->base_dir, *fmat);
+      if (this->params.use_custom_props) {
+        read_custom_properties(fmat->props, mat->id, this->params.props_enum_as_string);
+      }
     }
     this->mapping.mat_to_material.add(fmat, mat);
   }