[Bf-blender-cvs] [5b5811c97b5] master: USD: speed up large USD imports by not rebuilding material name map for each object

[Aras Pranckevicius]

Commit: 5b5811c97b59fd187a7aafd874535c749054d5db
Author: Aras Pranckevicius
Date:   Fri Jun 17 22:28:22 2022 +0300
Branches: master
https://developer.blender.org/rB5b5811c97b59fd187a7aafd874535c749054d5db

USD: speed up large USD imports by not rebuilding material name map for each object

Previous code was rebuilding "name to material" map for each object
being imported. Which means O(N*M) complexity (N=object count,
M=material count). There was already a TODO comment suggesting that
a single map that's maintained for the whole import would be enough.
This commit does exactly that.

While importing Moana USD scene (260k objects, 18k materials) this
saves about 6 minutes of import time.

Reviewed By: Bastien Montagne
Differential Revision: https://developer.blender.org/D15222

===================================================================

M	source/blender/io/usd/intern/usd_reader_mesh.cc
M	source/blender/io/usd/intern/usd_reader_prim.h

===================================================================

diff --git a/source/blender/io/usd/intern/usd_reader_mesh.cc b/source/blender/io/usd/intern/usd_reader_mesh.cc
index 368d0e1bab9..36e1a40953c 100644
--- a/source/blender/io/usd/intern/usd_reader_mesh.cc
+++ b/source/blender/io/usd/intern/usd_reader_mesh.cc
@@ -111,6 +111,7 @@ static void assign_materials(Main *bmain,
                              const std::map<pxr::SdfPath, int> &mat_index_map,
                              const USDImportParams &params,
                              pxr::UsdStageRefPtr stage,
+                             std::map<std::string, Material *> &mat_name_to_mat,
                              std::map<std::string, std::string> &usd_path_to_mat_name)
 {
   if (!(stage && bmain && ob)) {
@@ -132,16 +133,12 @@ static void assign_materials(Main *bmain,
     return;
   }
 
-  /* TODO(kevin): use global map? */
-  std::map<std::string, Material *> mat_map;
-  build_mat_map(bmain, &mat_map);
-
   blender::io::usd::USDMaterialReader mat_reader(params, bmain);
 
   for (it = mat_index_map.begin(); it != mat_index_map.end(); ++it) {
 
     Material *assigned_mat = find_existing_material(
-        it->first, params, mat_map, usd_path_to_mat_name);
+        it->first, params, mat_name_to_mat, usd_path_to_mat_name);
     if (!assigned_mat) {
       /* Blender material doesn't exist, so create it now. */
 
@@ -165,7 +162,7 @@ static void assign_materials(Main *bmain,
       }
 
       const std::string mat_name = pxr::TfMakeValidIdentifier(assigned_mat->id.name + 2);
-      mat_map[mat_name] = assigned_mat;
+      mat_name_to_mat[mat_name] = assigned_mat;
 
       if (params.mtl_name_collision_mode == USD_MTL_NAME_COLLISION_MAKE_UNIQUE) {
         /* Record the name of the Blender material we created for the USD material
@@ -805,11 +802,16 @@ void USDMeshReader::readFaceSetsSample(Main *bmain, Mesh *mesh, const double mot
 
   std::map<pxr::SdfPath, int> mat_map;
   assign_facesets_to_mpoly(motionSampleTime, mesh->mpoly, mesh->totpoly, &mat_map);
+  /* Build material name map if it's not built yet. */
+  if (this->settings_->mat_name_to_mat.empty()) {
+    utils::build_mat_map(bmain, &this->settings_->mat_name_to_mat);
+  }
   utils::assign_materials(bmain,
                           object_,
                           mat_map,
                           this->import_params_,
                           this->prim_.GetStage(),
+                          this->settings_->mat_name_to_mat,
                           this->settings_->usd_path_to_mat_name);
 }
 
diff --git a/source/blender/io/usd/intern/usd_reader_prim.h b/source/blender/io/usd/intern/usd_reader_prim.h
index f2df00accf6..c44c4a14ad7 100644
--- a/source/blender/io/usd/intern/usd_reader_prim.h
+++ b/source/blender/io/usd/intern/usd_reader_prim.h
@@ -11,6 +11,7 @@
 #include <string>
 
 struct Main;
+struct Material;
 struct Object;
 
 namespace blender::io::usd {
@@ -42,6 +43,10 @@ struct ImportSettings {
    * of what the importer is doing. This is necessary even
    * when all the other import settings are to remain const. */
   mutable std::map<std::string, std::string> usd_path_to_mat_name;
+  /* Map a material name to Blender material.
+   * This map is updated by readers during stage traversal,
+   * and is mutable similar to the map above. */
+  mutable std::map<std::string, Material *> mat_name_to_mat;
 
   ImportSettings()
       : do_convert_mat(false),