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

1 files changed, 49 insertions, 0 deletions

diff --git a/build_files/cmake/Modules/FindNanoVDB.cmake b/build_files/cmake/Modules/FindNanoVDB.cmake
new file mode 100644
index 00000000000..95d76fb39af
--- /dev/null
+++ b/build_files/cmake/Modules/FindNanoVDB.cmake
@@ -0,0 +1,49 @@
+# - Find NanoVDB library
+# Find the native NanoVDB includes and library
+# This module defines
+#  NANOVDB_INCLUDE_DIRS, where to find nanovdb.h, Set when
+#                         NANOVDB_INCLUDE_DIR is found.
+#  NANOVDB_ROOT_DIR, The base directory to search for NanoVDB.
+#                     This can also be an environment variable.
+#  NANOVDB_FOUND, If false, do not try to use NanoVDB.
+
+#=============================================================================
+# Copyright 2020 Blender Foundation.
+#
+# Distributed under the OSI-approved BSD 3-Clause License,
+# see accompanying file BSD-3-Clause-license.txt for details.
+#=============================================================================
+
+# If NANOVDB_ROOT_DIR was defined in the environment, use it.
+IF(NOT NANOVDB_ROOT_DIR AND NOT $ENV{NANOVDB_ROOT_DIR} STREQUAL "")
+  SET(NANOVDB_ROOT_DIR $ENV{NANOVDB_ROOT_DIR})
+ENDIF()
+
+SET(_nanovdb_SEARCH_DIRS
+  ${NANOVDB_ROOT_DIR}
+)
+
+FIND_PATH(NANOVDB_INCLUDE_DIR
+  NAMES
+    nanovdb/NanoVDB.h
+  HINTS
+    ${_nanovdb_SEARCH_DIRS}
+  PATH_SUFFIXES
+    include
+)
+
+# handle the QUIETLY and REQUIRED arguments and set NANOVDB_FOUND to TRUE if
+# all listed variables are TRUE
+INCLUDE(FindPackageHandleStandardArgs)
+FIND_PACKAGE_HANDLE_STANDARD_ARGS(NanoVDB DEFAULT_MSG
+    NANOVDB_INCLUDE_DIR)
+
+IF(NANOVDB_FOUND)
+  SET(NANOVDB_INCLUDE_DIRS ${NANOVDB_INCLUDE_DIR})
+ENDIF(NANOVDB_FOUND)
+
+MARK_AS_ADVANCED(
+  NANOVDB_INCLUDE_DIR
+)
+
+UNSET(_nanovdb_SEARCH_DIRS)