Cycles: Add half precision float support for volumes with NanoVDB

This patch makes it possible to change the precision with which to
store volume data in the NanoVDB data structure (as float, half, or
using variable bit quantization) via the previously unused precision
field in the volume data block.
It makes it possible to further reduce memory usage during
rendering, at a slight cost to the visual detail of a volume.

Differential Revision: https://developer.blender.org/D10023

5 files changed, 44 insertions, 7 deletions

diff --git a/intern/cycles/scene/image.cpp b/intern/cycles/scene/image.cpp
index c61ad1f1d71..2aa9a6bc1a1 100644
--- a/intern/cycles/scene/image.cpp
+++ b/intern/cycles/scene/image.cpp
@@ -64,6 +64,10 @@ const char *name_from_type(ImageDataType type)
       return "nanovdb_float";
     case IMAGE_DATA_TYPE_NANOVDB_FLOAT3:
       return "nanovdb_float3";
+    case IMAGE_DATA_TYPE_NANOVDB_FPN:
+      return "nanovdb_fpn";
+    case IMAGE_DATA_TYPE_NANOVDB_FP16:
+      return "nanovdb_fp16";
     case IMAGE_DATA_NUM_TYPES:
       assert(!"System enumerator type, should never be used");
       return "";
@@ -378,7 +382,9 @@ void ImageManager::load_image_metadata(Image *img)
   metadata.detect_colorspace();
 
   assert(features.has_nanovdb || (metadata.type != IMAGE_DATA_TYPE_NANOVDB_FLOAT ||
-                                  metadata.type != IMAGE_DATA_TYPE_NANOVDB_FLOAT3));
+                                  metadata.type != IMAGE_DATA_TYPE_NANOVDB_FLOAT3 ||
+                                  metadata.type != IMAGE_DATA_TYPE_NANOVDB_FPN ||
+                                  metadata.type != IMAGE_DATA_TYPE_NANOVDB_FP16));
 
   img->need_metadata = false;
 }
@@ -796,7 +802,8 @@ void ImageManager::device_load_image(Device *device, Scene *scene, int slot, Pro
     }
   }
 #ifdef WITH_NANOVDB
-  else if (type == IMAGE_DATA_TYPE_NANOVDB_FLOAT || type == IMAGE_DATA_TYPE_NANOVDB_FLOAT3) {
+  else if (type == IMAGE_DATA_TYPE_NANOVDB_FLOAT || type == IMAGE_DATA_TYPE_NANOVDB_FLOAT3 ||
+           type == IMAGE_DATA_TYPE_NANOVDB_FPN || type == IMAGE_DATA_TYPE_NANOVDB_FP16) {
     thread_scoped_lock device_lock(device_mutex);
     void *pixels = img->mem->alloc(img->metadata.byte_size, 0);
 
diff --git a/intern/cycles/scene/image_oiio.cpp b/intern/cycles/scene/image_oiio.cpp
index 3f825afbe90..1b7f8f49696 100644
--- a/intern/cycles/scene/image_oiio.cpp
+++ b/intern/cycles/scene/image_oiio.cpp
@@ -199,6 +199,8 @@ bool OIIOImageLoader::load_pixels(const ImageMetaData &metadata,
       break;
     case IMAGE_DATA_TYPE_NANOVDB_FLOAT:
     case IMAGE_DATA_TYPE_NANOVDB_FLOAT3:
+    case IMAGE_DATA_TYPE_NANOVDB_FPN:
+    case IMAGE_DATA_TYPE_NANOVDB_FP16:
     case IMAGE_DATA_NUM_TYPES:
       break;
   }
diff --git a/intern/cycles/scene/image_vdb.cpp b/intern/cycles/scene/image_vdb.cpp
index b6f0911fa2c..d0b41a239df 100644
--- a/intern/cycles/scene/image_vdb.cpp
+++ b/intern/cycles/scene/image_vdb.cpp
@@ -44,14 +44,30 @@ struct ToDenseOp {
 #  ifdef WITH_NANOVDB
 struct ToNanoOp {
   nanovdb::GridHandle<> nanogrid;
+  int precision;
 
   template<typename GridType, typename FloatGridType, typename FloatDataType, int channels>
   bool operator()(const openvdb::GridBase::ConstPtr &grid)
   {
     if constexpr (!std::is_same_v<GridType, openvdb::MaskGrid>) {
       try {
-        nanogrid = nanovdb::openToNanoVDB(
-            FloatGridType(*openvdb::gridConstPtrCast<GridType>(grid)));
+        FloatGridType floatgrid(*openvdb::gridConstPtrCast<GridType>(grid));
+        if constexpr (std::is_same_v<FloatGridType, openvdb::FloatGrid>) {
+          if (precision == 0) {
+            nanogrid = nanovdb::openToNanoVDB<nanovdb::HostBuffer,
+                                              typename FloatGridType::TreeType,
+                                              nanovdb::FpN>(floatgrid);
+            return true;
+          }
+          else if (precision == 16) {
+            nanogrid = nanovdb::openToNanoVDB<nanovdb::HostBuffer,
+                                              typename FloatGridType::TreeType,
+                                              nanovdb::Fp16>(floatgrid);
+            return true;
+          }
+        }
+
+        nanogrid = nanovdb::openToNanoVDB(floatgrid);
       }
       catch (const std::exception &e) {
         VLOG(1) << "Error converting OpenVDB to NanoVDB grid: " << e.what();
@@ -102,6 +118,7 @@ bool VDBImageLoader::load_metadata(const ImageDeviceFeatures &features, ImageMet
     openvdb::tools::pruneInactive(pruned_grid.tree());
     nanogrid = nanovdb::openToNanoVDB(pruned_grid);*/
     ToNanoOp op;
+    op.precision = precision;
     if (!openvdb::grid_type_operation(grid, op)) {
       return false;
     }
@@ -124,7 +141,15 @@ bool VDBImageLoader::load_metadata(const ImageDeviceFeatures &features, ImageMet
   if (nanogrid) {
     metadata.byte_size = nanogrid.size();
     if (metadata.channels == 1) {
-      metadata.type = IMAGE_DATA_TYPE_NANOVDB_FLOAT;
+      if (precision == 0) {
+        metadata.type = IMAGE_DATA_TYPE_NANOVDB_FPN;
+      }
+      else if (precision == 16) {
+        metadata.type = IMAGE_DATA_TYPE_NANOVDB_FP16;
+      }
+      else {
+        metadata.type = IMAGE_DATA_TYPE_NANOVDB_FLOAT;
+      }
     }
     else {
       metadata.type = IMAGE_DATA_TYPE_NANOVDB_FLOAT3;
diff --git a/intern/cycles/scene/image_vdb.h b/intern/cycles/scene/image_vdb.h
index a5fd51915ef..ea5f6b0b3d9 100644
--- a/intern/cycles/scene/image_vdb.h
+++ b/intern/cycles/scene/image_vdb.h
@@ -51,6 +51,7 @@ class VDBImageLoader : public ImageLoader {
 #endif
 #ifdef WITH_NANOVDB
   nanovdb::GridHandle<> nanogrid;
+  int precision = 0;
 #endif
 };
 
diff --git a/intern/cycles/scene/object.cpp b/intern/cycles/scene/object.cpp
index 8015be6393b..ddd89a16640 100644
--- a/intern/cycles/scene/object.cpp
+++ b/intern/cycles/scene/object.cpp
@@ -327,9 +327,11 @@ float Object::compute_volume_step_size() const
           /* Auto detect step size. */
           float3 size = one_float3();
 #ifdef WITH_NANOVDB
-          /* Dimensions were not applied to image transform with NanOVDB (see image_vdb.cpp) */
+          /* Dimensions were not applied to image transform with NanoVDB (see image_vdb.cpp) */
           if (metadata.type != IMAGE_DATA_TYPE_NANOVDB_FLOAT &&
-              metadata.type != IMAGE_DATA_TYPE_NANOVDB_FLOAT3)
+              metadata.type != IMAGE_DATA_TYPE_NANOVDB_FLOAT3 &&
+              metadata.type != IMAGE_DATA_TYPE_NANOVDB_FPN &&
+              metadata.type != IMAGE_DATA_TYPE_NANOVDB_FP16)
 #endif
             size /= make_float3(metadata.width, metadata.height, metadata.depth);