Cycles: load OpenVDB file earlier in Blender export

In an upcoming bugfix we'll use OpenVDB data structures directly to build mesh
for sparse OpenVDB volumes, loading them OpenVDB grids earlier and removing any
references to Blender data structures makes that easier.

This also makes changes to Blender volumes to support this, so Cycles can take
ownership of a grid without Blender having to keep its own reference to it.
This should also be useful in a future Python API.

Ref D8401

3 files changed, 21 insertions, 62 deletions

diff --git a/intern/cycles/blender/blender_volume.cpp b/intern/cycles/blender/blender_volume.cpp
index 80591e0eec8..d0e1e4d6131 100644
--- a/intern/cycles/blender/blender_volume.cpp
+++ b/intern/cycles/blender/blender_volume.cpp
@@ -217,43 +217,29 @@ static void sync_smoke_volume(Scene *scene, BL::Object &b_ob, Mesh *mesh, float
 class BlenderVolumeLoader : public VDBImageLoader {
  public:
   BlenderVolumeLoader(BL::BlendData &b_data, BL::Volume &b_volume, const string &grid_name)
-      : VDBImageLoader(grid_name), b_data(b_data), b_volume(b_volume), unload(false)
-  {
-  }
-
-  bool load_metadata(ImageMetaData &metadata) override
+      : VDBImageLoader(grid_name), b_volume(b_volume)
   {
     b_volume.grids.load(b_data.ptr.data);
-    BL::VolumeGrid b_volume_grid = find_grid();
-
-    if (!b_volume_grid) {
-      return false;
-    }
-
-    unload = !b_volume_grid.is_loaded();
 
 #ifdef WITH_OPENVDB
-    Volume *volume = (Volume *)b_volume.ptr.data;
-    VolumeGrid *volume_grid = (VolumeGrid *)b_volume_grid.ptr.data;
-    grid = BKE_volume_grid_openvdb_for_read(volume, volume_grid);
-#endif
+    BL::Volume::grids_iterator b_grid_iter;
+    for (b_volume.grids.begin(b_grid_iter); b_grid_iter != b_volume.grids.end(); ++b_grid_iter) {
+      BL::VolumeGrid b_volume_grid(*b_grid_iter);
+      if (b_volume_grid.name() == grid_name) {
+        const bool unload = !b_volume_grid.is_loaded();
 
-    return VDBImageLoader::load_metadata(metadata);
-  }
+        Volume *volume = (Volume *)b_volume.ptr.data;
+        VolumeGrid *volume_grid = (VolumeGrid *)b_volume_grid.ptr.data;
+        grid = BKE_volume_grid_openvdb_for_read(volume, volume_grid);
 
-  bool load_pixels(const ImageMetaData &metadata,
-                   void *pixels,
-                   const size_t pixel_size,
-                   const bool associate_alpha) override
-  {
-    b_volume.grids.load(b_data.ptr.data);
-    BL::VolumeGrid b_volume_grid = find_grid();
+        if (unload) {
+          b_volume_grid.unload();
+        }
 
-    if (!b_volume_grid) {
-      return false;
+        break;
+      }
     }
-
-    return VDBImageLoader::load_pixels(metadata, pixels, pixel_size, associate_alpha);
+#endif
   }
 
   bool equals(const ImageLoader &other) const override
@@ -263,36 +249,7 @@ class BlenderVolumeLoader : public VDBImageLoader {
     return b_volume == other_loader.b_volume && grid_name == other_loader.grid_name;
   }
 
-  void cleanup() override
-  {
-    VDBImageLoader::cleanup();
-
-    BL::VolumeGrid b_volume_grid = find_grid();
-    if (b_volume_grid && unload) {
-      b_volume_grid.unload();
-    }
-  }
-
-  /* Find grid with matching name. Grid point not stored in the class since
-   * grids may be unloaded before we load the pixels, for example for motion
-   * blur where we move between frames. */
-  BL::VolumeGrid find_grid()
-  {
-#ifdef WITH_OPENVDB
-    BL::Volume::grids_iterator b_grid_iter;
-    for (b_volume.grids.begin(b_grid_iter); b_grid_iter != b_volume.grids.end(); ++b_grid_iter) {
-      if (b_grid_iter->name() == grid_name) {
-        return *b_grid_iter;
-      }
-    }
-#endif
-
-    return BL::VolumeGrid(PointerRNA_NULL);
-  }
-
-  BL::BlendData b_data;
   BL::Volume b_volume;
-  bool unload;
 };
 
 static void sync_volume_object(BL::BlendData &b_data, BL::Object &b_ob, Scene *scene, Mesh *mesh)
@@ -342,7 +299,7 @@ static void sync_volume_object(BL::BlendData &b_data, BL::Object &b_ob, Scene *s
       ImageParams params;
       params.frame = b_volume.grids.frame();
 
-      attr->data_voxel() = scene->image_manager->add_image(loader, params);
+      attr->data_voxel() = scene->image_manager->add_image(loader, params, false);
     }
   }
 }
diff --git a/intern/cycles/render/image.cpp b/intern/cycles/render/image.cpp
index 8d187814d64..691eb162dd0 100644
--- a/intern/cycles/render/image.cpp
+++ b/intern/cycles/render/image.cpp
@@ -362,9 +362,11 @@ ImageHandle ImageManager::add_image(const string &filename,
   return handle;
 }
 
-ImageHandle ImageManager::add_image(ImageLoader *loader, const ImageParams &params)
+ImageHandle ImageManager::add_image(ImageLoader *loader,
+                                    const ImageParams &params,
+                                    const bool builtin)
 {
-  const int slot = add_image_slot(loader, params, true);
+  const int slot = add_image_slot(loader, params, builtin);
 
   ImageHandle handle;
   handle.tile_slots.push_back(slot);
diff --git a/intern/cycles/render/image.h b/intern/cycles/render/image.h
index fffe7c5152a..47be0ee559a 100644
--- a/intern/cycles/render/image.h
+++ b/intern/cycles/render/image.h
@@ -169,7 +169,7 @@ class ImageManager {
   ImageHandle add_image(const string &filename,
                         const ImageParams &params,
                         const vector<int> &tiles);
-  ImageHandle add_image(ImageLoader *loader, const ImageParams &params);
+  ImageHandle add_image(ImageLoader *loader, const ImageParams &params, const bool builtin = true);
 
   void device_update(Device *device, Scene *scene, Progress &progress);
   void device_update_slot(Device *device, Scene *scene, int slot, Progress *progress);