USD import: Handle material name collisions

This is a partial fix for T90535.

Added Material Name Collision USD import menu option, to specify
the behavior when USD materials in different namespaces have the
same name.

The Material Name Collision menu options are

- Make Unique: Import each USD material as a unique Blender material.
- Reference Existing: If a material with the same name already
exists, reference that instead of importing.

Previously, the default behavior was to always keep the existing
material. This was causing an issue in the ALab scene, where
dozens of different USD materials all have the same name,
usdpreviewsurface1, so that only one instance of these materials
would be imported.

Reviewed by: Sybren

Differential Revision: https://developer.blender.org/D14869

1 files changed, 28 insertions, 1 deletions

diff --git a/source/blender/editors/io/io_usd.c b/source/blender/editors/io/io_usd.c
index 45d658d5b25..a59cdf60243 100644
--- a/source/blender/editors/io/io_usd.c
+++ b/source/blender/editors/io/io_usd.c
@@ -57,6 +57,20 @@ const EnumPropertyItem rna_enum_usd_export_evaluation_mode_items[] = {
     {0, NULL, 0, NULL, NULL},
 };
 
+const EnumPropertyItem rna_enum_usd_mtl_name_collision_mode_items[] = {
+    {USD_MTL_NAME_COLLISION_MAKE_UNIQUE,
+     "MAKE_UNIQUE",
+     0,
+     "Make Unique",
+     "Import each USD material as a unique Blender material"},
+    {USD_MTL_NAME_COLLISION_REFERENCE_EXISTING,
+     "REFERENCE_EXISTING",
+     0,
+     "Reference Existing",
+     "If a material with the same name already exists, reference that instead of importing"},
+    {0, NULL, 0, NULL, NULL},
+};
+
 /* Stored in the wmOperator's customdata field to indicate it should run as a background job.
  * This is set when the operator is invoked, and not set when it is only executed. */
 enum { AS_BACKGROUND_JOB = 1 };
@@ -371,6 +385,9 @@ static int wm_usd_import_exec(bContext *C, wmOperator *op)
 
   const float light_intensity_scale = RNA_float_get(op->ptr, "light_intensity_scale");
 
+  const eUSDMtlNameCollisionMode mtl_name_collision_mode = RNA_enum_get(op->ptr,
+                                                                        "mtl_name_collision_mode");
+
   /* TODO(makowalski): Add support for sequences. */
   const bool is_sequence = false;
   int offset = 0;
@@ -409,7 +426,8 @@ static int wm_usd_import_exec(bContext *C, wmOperator *op)
                                    .use_instancing = use_instancing,
                                    .import_usd_preview = import_usd_preview,
                                    .set_material_blend = set_material_blend,
-                                   .light_intensity_scale = light_intensity_scale};
+                                   .light_intensity_scale = light_intensity_scale,
+                                   .mtl_name_collision_mode = mtl_name_collision_mode};
 
   const bool ok = USD_import(C, filename, &params, as_background_job);
 
@@ -452,6 +470,7 @@ static void wm_usd_import_draw(bContext *UNUSED(C), wmOperator *op)
   uiItemR(col, ptr, "relative_path", 0, NULL, ICON_NONE);
   uiItemR(col, ptr, "create_collection", 0, NULL, ICON_NONE);
   uiItemR(box, ptr, "light_intensity_scale", 0, NULL, ICON_NONE);
+  uiItemR(box, ptr, "mtl_name_collision_mode", 0, NULL, ICON_NONE);
 
   box = uiLayoutBox(layout);
   col = uiLayoutColumnWithHeading(box, true, IFACE_("Experimental"));
@@ -575,6 +594,14 @@ void WM_OT_usd_import(struct wmOperatorType *ot)
                 "Scale for the intensity of imported lights",
                 0.0001f,
                 1000.0f);
+
+  RNA_def_enum(
+      ot->srna,
+      "mtl_name_collision_mode",
+      rna_enum_usd_mtl_name_collision_mode_items,
+      USD_MTL_NAME_COLLISION_MAKE_UNIQUE,
+      "Material Name Collision",
+      "Behavior when the name of an imported material conflicts with an existing material");
 }
 
 #endif /* WITH_USD */