gltfpack: Add temporary command line option to disable mesh deduplica…

…tion

In theory, deduplication should not result in any issues as any changes
only concern the internal file structure, and it should be beneficial in
most cases (and when it's penalizing draw call counts, existing options
provide enough control), but just in case we now can disable this
feature entirely using -mdd.

The goal is to remove this option in the future, it's just here in case
anyone reports issues in the wild.

Not running dedupMeshes means no mesh has geometry_duplicate flag set,
so no dedup related code activates.

gltf/gltfpack.cpp

@@ -347,7 +347,8 @@ static void process(cgltf_data* data, const char* input_path, const char* output
 	markAnimated(data, nodes, animations);
 
 	mergeMeshMaterials(data, meshes, settings);
-	dedupMeshes(meshes);
+	if (settings.mesh_dedup)
+		dedupMeshes(meshes);
 
 	for (size_t i = 0; i < meshes.size(); ++i)
 		detachMesh(meshes[i], data, nodes, settings);
@@ -427,7 +428,6 @@ static void process(cgltf_data* data, const char* input_path, const char* output
 	meshes.insert(meshes.end(), debug_meshes.begin(), debug_meshes.end());
 #endif
 
-
 	filterEmptyMeshes(meshes); // some meshes may become empty after processing
 
 	QuantizationPosition qp = prepareQuantizationPosition(meshes, settings);
@@ -1186,6 +1186,7 @@ Settings defaults()
 	settings.rot_bits = 12;
 	settings.scl_bits = 16;
 	settings.anim_freq = 30;
+	settings.mesh_dedup = true;
 	settings.simplify_ratio = 1.f;
 	settings.simplify_error = 1e-2f;
 	settings.texture_scale = 1.f;
@@ -1323,6 +1324,11 @@ int main(int argc, char** argv)
 		{
 			settings.keep_attributes = true;
 		}
+		else if (strcmp(arg, "-mdd") == 0)
+		{
+			fprintf(stderr, "Warning: option -mdd disables mesh deduplication and is only provided as a safety measure; it will be removed in the future\n");
+			settings.mesh_dedup = false;
+		}
 		else if (strcmp(arg, "-mm") == 0)
 		{
 			settings.mesh_merge = true;

gltf/gltfpack.h

@@ -134,6 +134,7 @@ struct Settings
 	bool keep_extras;
 	bool keep_attributes;
 
+	bool mesh_dedup;
 	bool mesh_merge;
 	bool mesh_instancing;