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, 18 insertions, 3 deletions

diff --git a/source/blender/io/usd/intern/usd_hierarchy_iterator.cc b/source/blender/io/usd/intern/usd_hierarchy_iterator.cc
index 7a0d896fb3e..51261c4d91e 100644
--- a/source/blender/io/usd/intern/usd_hierarchy_iterator.cc
+++ b/source/blender/io/usd/intern/usd_hierarchy_iterator.cc
@@ -10,6 +10,7 @@
 #include "usd_writer_mesh.h"
 #include "usd_writer_metaball.h"
 #include "usd_writer_transform.h"
+#include "usd_writer_volume.h"
 
 #include <string>
 
@@ -28,10 +29,11 @@
 
 namespace blender::io::usd {
 
-USDHierarchyIterator::USDHierarchyIterator(Depsgraph *depsgraph,
+USDHierarchyIterator::USDHierarchyIterator(Main *bmain,
+                                           Depsgraph *depsgraph,
                                            pxr::UsdStageRefPtr stage,
                                            const USDExportParams &params)
-    : AbstractHierarchyIterator(depsgraph), stage_(stage), params_(params)
+    : AbstractHierarchyIterator(bmain, depsgraph), stage_(stage), params_(params)
 {
 }
 
@@ -59,6 +61,15 @@ void USDHierarchyIterator::set_export_frame(float frame_nr)
   export_time_ = pxr::UsdTimeCode(frame_nr);
 }
 
+std::string USDHierarchyIterator::get_export_file_path() const
+{
+  /* Returns the same path that was passed to `stage_` object during it's creation (via
+   * `pxr::UsdStage::CreateNew` function). */
+  const pxr::SdfLayerHandle root_layer = stage_->GetRootLayer();
+  const std::string usd_export_file_path = root_layer->GetRealPath();
+  return usd_export_file_path;
+}
+
 const pxr::UsdTimeCode &USDHierarchyIterator::get_export_time_code() const
 {
   return export_time_;
@@ -66,7 +77,8 @@ const pxr::UsdTimeCode &USDHierarchyIterator::get_export_time_code() const
 
 USDExporterContext USDHierarchyIterator::create_usd_export_context(const HierarchyContext *context)
 {
-  return USDExporterContext{depsgraph_, stage_, pxr::SdfPath(context->export_path), this, params_};
+  return USDExporterContext{
+      bmain_, depsgraph_, stage_, pxr::SdfPath(context->export_path), this, params_};
 }
 
 AbstractHierarchyWriter *USDHierarchyIterator::create_transform_writer(
@@ -93,6 +105,9 @@ AbstractHierarchyWriter *USDHierarchyIterator::create_data_writer(const Hierarch
     case OB_MBALL:
       data_writer = new USDMetaballWriter(usd_export_context);
       break;
+    case OB_VOLUME:
+      data_writer = new USDVolumeWriter(usd_export_context);
+      break;
 
     case OB_EMPTY:
     case OB_CURVES_LEGACY: