Refactor: move default initialization of USDExportParams to definition

Matching the default file export settings.

source/blender/io/usd/hydra/usd_scene_delegate.cc

@@ -44,19 +44,11 @@ USDSceneDelegate::~USDSceneDelegate()
 
 void USDSceneDelegate::populate(Depsgraph *depsgraph)
 {
-  USDExportParams params = {};
-  params.export_hair = true;
-  params.export_uvmaps = true;
-  params.export_normals = true;
-  params.export_materials = true;
-  params.selected_objects_only = false;
-  params.visible_objects_only = true;
+  USDExportParams params;
   params.use_instancing = true;
+  params.relative_paths = false;  /* Unnecessary. */
+  params.export_textures = false; /* Don't copy all textures, is slow. */
   params.evaluation_mode = DEG_get_mode(depsgraph);
-  params.generate_preview_surface = true;
-  params.export_textures = true;
-  params.overwrite_textures = true;
-  params.relative_paths = true;
 
   /* Create clean directory for export. */
   BLI_delete(temp_dir_.c_str(), true, true);

source/blender/io/usd/tests/usd_curves_test.cc

@@ -109,7 +109,7 @@ TEST_F(UsdCurvesTest, usd_export_curves)
   /* File sanity check. */
   EXPECT_EQ(BLI_listbase_count(&bfile->main->objects), 6);
 
-  USDExportParams params{};
+  USDExportParams params;
 
   const bool result = USD_export(context, output_filename.c_str(), &params, false);
   EXPECT_TRUE(result) << "USD export should succed.";

source/blender/io/usd/tests/usd_export_test.cc

@@ -209,10 +209,11 @@ TEST_F(UsdExportTest, usd_export_rain_mesh)
   /* File sanity check. */
   EXPECT_EQ(BLI_listbase_count(&bfile->main->objects), 3);
 
-  USDExportParams params{};
+  USDExportParams params;
+  params.export_materials = false;
   params.export_normals = true;
+  params.export_uvmaps = false;
   params.visible_objects_only = true;
-  params.evaluation_mode = eEvaluationMode::DAG_EVAL_VIEWPORT;
 
   bool result = USD_export(context, output_filename.c_str(), &params, false);
   ASSERT_TRUE(result) << "Writing to " << output_filename << " failed!";
@@ -272,12 +273,13 @@ TEST_F(UsdExportTest, usd_export_material)
 
   EXPECT_TRUE(bool(material));
 
-  USDExportParams params{};
-  params.export_normals = true;
+  USDExportParams params;
   params.export_materials = true;
-  params.generate_preview_surface = true;
+  params.export_normals = true;
+  params.export_textures = false;
   params.export_uvmaps = true;
-  params.evaluation_mode = eEvaluationMode::DAG_EVAL_VIEWPORT;
+  params.generate_preview_surface = true;
+  params.relative_paths = false;
 
   const bool result = USD_export(context, output_filename.c_str(), &params, false);
   ASSERT_TRUE(result) << "Unable to export stage to " << output_filename;

source/blender/io/usd/tests/usd_usdz_export_test.cc

@@ -94,7 +94,9 @@ TEST_F(UsdUsdzExportTest, usdz_export)
       << "BLI_current_working_dir is not expected to return a different value than the given char "
          "buffer.";
 
-  USDExportParams params{};
+  USDExportParams params;
+  params.export_materials = false;
+  params.visible_objects_only = false;
 
   bool result = USD_export(context, output_filepath, &params, false);
   ASSERT_TRUE(result) << "usd export to " << output_filepath << " failed.";

source/blender/io/usd/usd.h

@@ -38,20 +38,20 @@ typedef enum eUSDTexNameCollisionMode {
 } eUSDTexNameCollisionMode;
 
 struct USDExportParams {
-  bool export_animation;
-  bool export_hair;
-  bool export_uvmaps;
-  bool export_normals;
-  bool export_materials;
-  bool selected_objects_only;
-  bool visible_objects_only;
-  bool use_instancing;
-  enum eEvaluationMode evaluation_mode;
-  bool generate_preview_surface;
-  bool export_textures;
-  bool overwrite_textures;
-  bool relative_paths;
-  char root_prim_path[1024]; /* FILE_MAX */
+  bool export_animation = false;
+  bool export_hair = true;
+  bool export_uvmaps = true;
+  bool export_normals = true;
+  bool export_materials = true;
+  bool selected_objects_only = false;
+  bool visible_objects_only = true;
+  bool use_instancing = false;
+  enum eEvaluationMode evaluation_mode = DAG_EVAL_VIEWPORT;
+  bool generate_preview_surface = true;
+  bool export_textures = true;
+  bool overwrite_textures = true;
+  bool relative_paths = true;
+  char root_prim_path[1024] = ""; /* FILE_MAX */
 };
 
 struct USDImportParams {