USD: add volume/VDB export

Add support for volume (OpenVDB) USD export:

- Allows to export both static and animated volumes.
- Supports volumes that have OpenVDB data from files or are generated in
  Blender with 'Mesh to Volume' modifier.
- For volumes that have generated data in Blender it also exports
  corresponding .vdb files. Those files are saved in a new folder named
  "volumes".
- Slightly changes the USD export UI panel. "Relative Texture Paths"
  becomes "Relative Paths" (and has separate UI box) as the
  functionality will now apply to both textures and volumes. Disabling
  of this option due to "Materials" checkbox being turned off has been
  removed.

Reviewed By: sybren, makowalski

Differential Revision: https://developer.blender.org/D14193

Manifest Task: T95407

1 files changed, 3 insertions, 7 deletions

diff --git a/source/blender/io/usd/intern/usd_writer_material.cc b/source/blender/io/usd/intern/usd_writer_material.cc
index 1bfc0e50f69..a24877a20bd 100644
--- a/source/blender/io/usd/intern/usd_writer_material.cc
+++ b/source/blender/io/usd/intern/usd_writer_material.cc
@@ -576,7 +576,7 @@ static std::string get_tex_image_asset_path(bNode *node,
     char file_path[FILE_MAX];
     BLI_split_file_part(path.c_str(), file_path, FILE_MAX);
 
-    if (export_params.relative_texture_paths) {
+    if (export_params.relative_paths) {
       BLI_path_join(exp_path, FILE_MAX, ".", "textures", file_path, nullptr);
     }
     else {
@@ -594,7 +594,7 @@ static std::string get_tex_image_asset_path(bNode *node,
     return exp_path;
   }
 
-  if (export_params.relative_texture_paths) {
+  if (export_params.relative_paths) {
     /* Get the path relative to the USD. */
     pxr::SdfLayerHandle layer = stage->GetRootLayer();
     std::string stage_path = layer->GetRealPath();
@@ -606,11 +606,7 @@ static std::string get_tex_image_asset_path(bNode *node,
     strcpy(rel_path, path.c_str());
 
     BLI_path_rel(rel_path, stage_path.c_str());
-
-    /* BLI_path_rel adds '//' as a prefix to the path, if
-     * generating the relative path was successful. */
-    if (rel_path[0] != '/' || rel_path[1] != '/') {
-      /* No relative path generated. */
+    if (!BLI_path_is_rel(rel_path)) {
       return path;
     }