Add ext/openvdb for nanovdb

.gitmodules

@@ -17,3 +17,7 @@
 [submodule "src/ext/filesystem"]
 	path = src/ext/filesystem
 	url = https://github.com/wjakob/filesystem.git
+[submodule "src/ext/openvdb"]
+	path = src/ext/openvdb
+	url = https://github.com/AcademySoftwareFoundation/openvdb.git
+	branch = feature/nanovdb

CMakeLists.txt

@@ -56,6 +56,7 @@ check_ext ("Ptex" "ptex/src" 82bd326)
 check_ext ("double-conversion" "double-conversion/cmake" 9a8e518)
 check_ext ("filesystem" "filesystem/filesystem" 4efd2628)
 check_ext ("stb" "stb/tools" 1034f5)
+check_ext ("OpenVDB" "openvdb/nanovdb" d5ea9808f)
 check_ext ("zlib" "zlib/doc" 54d591e)
 
 if (CMAKE_BUILD_TYPE MATCHES Release)
@@ -165,6 +166,7 @@ if (CMAKE_CUDA_COMPILER)
         # FIXME. Sigh. I'm not sure how else to pass this through to cuda_compile_ptx...
         include_directories (src)
         include_directories (${CMAKE_BINARY_DIR})
+        include_directories (${NANOVDB_INCLUDE})
 
         # from Ingo's configure_optix.cmake (Apache licensed)
         find_program (BIN2C bin2c DOC "Path to the CUDA SDK bin2c executable.")
@@ -656,6 +658,7 @@ target_include_directories (pbrt_lib PUBLIC
   ${FILESYSTEM_INCLUDE}
   ${PTEX_INCLUDE}
   ${DOUBLE_CONVERSION_INCLUDE}
+  ${NANOVDB_INCLUDE}
   ${CMAKE_CURRENT_BINARY_DIR}
 )
 

src/ext/CMakeLists.txt

@@ -96,3 +96,7 @@ set (DOUBLE_CONVERSION_INCLUDE ${CMAKE_CURRENT_SOURCE_DIR}/double-conversion PAR
 
 set_property (TARGET double-conversion cctest PROPERTY FOLDER "ext")
 
+###########################################################################
+# nanovdb
+
+set (NANOVDB_INCLUDE ${CMAKE_CURRENT_SOURCE_DIR}/openvdb/nanovdb PARENT_SCOPE)