Cycles: Add NanoVDB support for rendering volumes

NanoVDB is a platform-independent sparse volume data structure that makes it possible to
use OpenVDB volumes on the GPU. This patch uses it for volume rendering in Cycles,
replacing the previous usage of dense 3D textures.

Since it has a big impact on memory usage and performance and changes the OpenVDB
branch used for the rest of Blender as well, this is not enabled by default yet, which will
happen only after 2.82 was branched off. To enable it, build both dependencies and Blender
itself with the "WITH_NANOVDB" CMake option.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D8794

6 files changed, 83 insertions, 1 deletions

diff --git a/intern/cycles/render/CMakeLists.txt b/intern/cycles/render/CMakeLists.txt
index 43e66aa4e5b..9663e25cd93 100644
--- a/intern/cycles/render/CMakeLists.txt
+++ b/intern/cycles/render/CMakeLists.txt
@@ -144,6 +144,12 @@ if(WITH_OPENVDB)
   )
 endif()
 
+if(WITH_NANOVDB)
+  list(APPEND INC_SYS
+    ${NANOVDB_INCLUDE_DIRS}
+  )
+endif()
+
 include_directories(${INC})
 include_directories(SYSTEM ${INC_SYS})
 
diff --git a/intern/cycles/render/image.cpp b/intern/cycles/render/image.cpp
index fd6186d8f1e..e50e70c8591 100644
--- a/intern/cycles/render/image.cpp
+++ b/intern/cycles/render/image.cpp
@@ -73,6 +73,10 @@ const char *name_from_type(ImageDataType type)
       return "ushort4";
     case IMAGE_DATA_TYPE_USHORT:
       return "ushort";
+    case IMAGE_DATA_TYPE_NANOVDB_FLOAT:
+      return "nanovdb_float";
+    case IMAGE_DATA_TYPE_NANOVDB_FLOAT3:
+      return "nanovdb_float3";
     case IMAGE_DATA_NUM_TYPES:
       assert(!"System enumerator type, should never be used");
       return "";
@@ -210,6 +214,7 @@ ImageMetaData::ImageMetaData()
       width(0),
       height(0),
       depth(0),
+      byte_size(0),
       type(IMAGE_DATA_NUM_TYPES),
       colorspace(u_colorspace_raw),
       colorspace_file_format(""),
@@ -756,6 +761,16 @@ void ImageManager::device_load_image(Device *device, Scene *scene, int slot, Pro
       pixels[0] = TEX_IMAGE_MISSING_R;
     }
   }
+#ifdef WITH_NANOVDB
+  else if (type == IMAGE_DATA_TYPE_NANOVDB_FLOAT || type == IMAGE_DATA_TYPE_NANOVDB_FLOAT3) {
+    thread_scoped_lock device_lock(device_mutex);
+    void *pixels = img->mem->alloc(img->metadata.byte_size, 0);
+
+    if (pixels != NULL) {
+      img->loader->load_pixels(img->metadata, pixels, img->metadata.byte_size, false);
+    }
+  }
+#endif
 
   {
     thread_scoped_lock device_lock(device_mutex);
diff --git a/intern/cycles/render/image.h b/intern/cycles/render/image.h
index cb059256ce3..c9eccb3468a 100644
--- a/intern/cycles/render/image.h
+++ b/intern/cycles/render/image.h
@@ -77,6 +77,7 @@ class ImageMetaData {
   /* Set by ImageLoader.load_metadata(). */
   int channels;
   size_t width, height, depth;
+  size_t byte_size;
   ImageDataType type;
 
   /* Optional color space, defaults to raw. */
diff --git a/intern/cycles/render/image_oiio.cpp b/intern/cycles/render/image_oiio.cpp
index c4f95c6b4bc..e9c87461822 100644
--- a/intern/cycles/render/image_oiio.cpp
+++ b/intern/cycles/render/image_oiio.cpp
@@ -209,6 +209,8 @@ bool OIIOImageLoader::load_pixels(const ImageMetaData &metadata,
     case IMAGE_DATA_TYPE_FLOAT4:
       oiio_load_pixels<TypeDesc::FLOAT, float>(metadata, in, (float *)pixels);
       break;
+    case IMAGE_DATA_TYPE_NANOVDB_FLOAT:
+    case IMAGE_DATA_TYPE_NANOVDB_FLOAT3:
     case IMAGE_DATA_NUM_TYPES:
       break;
   }
diff --git a/intern/cycles/render/image_vdb.cpp b/intern/cycles/render/image_vdb.cpp
index 3f7dd45ee88..fc2cfe9874e 100644
--- a/intern/cycles/render/image_vdb.cpp
+++ b/intern/cycles/render/image_vdb.cpp
@@ -20,6 +20,9 @@
 #  include <openvdb/openvdb.h>
 #  include <openvdb/tools/Dense.h>
 #endif
+#ifdef WITH_NANOVDB
+#  include <nanovdb/util/OpenToNanoVDB.h>
+#endif
 
 CCL_NAMESPACE_BEGIN
 
@@ -53,41 +56,84 @@ bool VDBImageLoader::load_metadata(ImageMetaData &metadata)
   /* Set data type. */
   if (grid->isType<openvdb::FloatGrid>()) {
     metadata.channels = 1;
+#  ifdef WITH_NANOVDB
+    nanogrid = nanovdb::openToNanoVDB(*openvdb::gridConstPtrCast<openvdb::FloatGrid>(grid));
+#  endif
   }
   else if (grid->isType<openvdb::Vec3fGrid>()) {
     metadata.channels = 3;
+#  ifdef WITH_NANOVDB
+    nanogrid = nanovdb::openToNanoVDB(*openvdb::gridConstPtrCast<openvdb::Vec3fGrid>(grid));
+#  endif
   }
   else if (grid->isType<openvdb::BoolGrid>()) {
     metadata.channels = 1;
+#  ifdef WITH_NANOVDB
+    nanogrid = nanovdb::openToNanoVDB(
+        openvdb::FloatGrid(*openvdb::gridConstPtrCast<openvdb::BoolGrid>(grid)));
+#  endif
   }
   else if (grid->isType<openvdb::DoubleGrid>()) {
     metadata.channels = 1;
+#  ifdef WITH_NANOVDB
+    nanogrid = nanovdb::openToNanoVDB(
+        openvdb::FloatGrid(*openvdb::gridConstPtrCast<openvdb::DoubleGrid>(grid)));
+#  endif
   }
   else if (grid->isType<openvdb::Int32Grid>()) {
     metadata.channels = 1;
+#  ifdef WITH_NANOVDB
+    nanogrid = nanovdb::openToNanoVDB(
+        openvdb::FloatGrid(*openvdb::gridConstPtrCast<openvdb::Int32Grid>(grid)));
+#  endif
   }
   else if (grid->isType<openvdb::Int64Grid>()) {
     metadata.channels = 1;
+#  ifdef WITH_NANOVDB
+    nanogrid = nanovdb::openToNanoVDB(
+        openvdb::FloatGrid(*openvdb::gridConstPtrCast<openvdb::Int64Grid>(grid)));
+#  endif
   }
   else if (grid->isType<openvdb::Vec3IGrid>()) {
     metadata.channels = 3;
+#  ifdef WITH_NANOVDB
+    nanogrid = nanovdb::openToNanoVDB(
+        openvdb::Vec3fGrid(*openvdb::gridConstPtrCast<openvdb::Vec3IGrid>(grid)));
+#  endif
   }
   else if (grid->isType<openvdb::Vec3dGrid>()) {
     metadata.channels = 3;
+#  ifdef WITH_NANOVDB
+    nanogrid = nanovdb::openToNanoVDB(
+        openvdb::Vec3fGrid(*openvdb::gridConstPtrCast<openvdb::Vec3dGrid>(grid)));
+#  endif
   }
   else if (grid->isType<openvdb::MaskGrid>()) {
     metadata.channels = 1;
+#  ifdef WITH_NANOVDB
+    return false;  // Unsupported
+#  endif
   }
   else {
     return false;
   }
 
+#  ifdef WITH_NANOVDB
+  metadata.byte_size = nanogrid.size();
+  if (metadata.channels == 1) {
+    metadata.type = IMAGE_DATA_TYPE_NANOVDB_FLOAT;
+  }
+  else {
+    metadata.type = IMAGE_DATA_TYPE_NANOVDB_FLOAT3;
+  }
+#  else
   if (metadata.channels == 1) {
     metadata.type = IMAGE_DATA_TYPE_FLOAT;
   }
   else {
     metadata.type = IMAGE_DATA_TYPE_FLOAT4;
   }
+#  endif
 
   /* Set transform from object space to voxel index. */
   openvdb::math::Mat4f grid_matrix = grid->transform().baseMap()->getAffineMap()->getMat4();
@@ -113,7 +159,10 @@ bool VDBImageLoader::load_metadata(ImageMetaData &metadata)
 
 bool VDBImageLoader::load_pixels(const ImageMetaData &, void *pixels, const size_t, const bool)
 {
-#ifdef WITH_OPENVDB
+#if defined(WITH_NANOVDB)
+  memcpy(pixels, nanogrid.data(), nanogrid.size());
+  return true;
+#elif defined(WITH_OPENVDB)
   if (grid->isType<openvdb::FloatGrid>()) {
     openvdb::tools::Dense<float, openvdb::tools::LayoutXYZ> dense(bbox, (float *)pixels);
     openvdb::tools::copyToDense(*openvdb::gridConstPtrCast<openvdb::FloatGrid>(grid), dense);
@@ -183,6 +232,9 @@ void VDBImageLoader::cleanup()
   /* Free OpenVDB grid memory as soon as we can. */
   grid.reset();
 #endif
+#ifdef WITH_NANOVDB
+  nanogrid.reset();
+#endif
 }
 
 bool VDBImageLoader::is_vdb_loader() const
diff --git a/intern/cycles/render/image_vdb.h b/intern/cycles/render/image_vdb.h
index 4500cfbfb88..71d10cc39f5 100644
--- a/intern/cycles/render/image_vdb.h
+++ b/intern/cycles/render/image_vdb.h
@@ -20,6 +20,9 @@
 #ifdef WITH_OPENVDB
 #  include <openvdb/openvdb.h>
 #endif
+#ifdef WITH_NANOVDB
+#  include <nanovdb/util/GridHandle.h>
+#endif
 
 #include "render/image.h"
 
@@ -55,6 +58,9 @@ class VDBImageLoader : public ImageLoader {
   openvdb::GridBase::ConstPtr grid;
   openvdb::CoordBBox bbox;
 #endif
+#ifdef WITH_NANOVDB
+  nanovdb::GridHandle<> nanogrid;
+#endif
 };
 
 CCL_NAMESPACE_END