Implement KHR_draco_mesh_compression extension

CMakeLists.txt

@@ -6,6 +6,8 @@ set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
 
+set(CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
+
 # Find USD - only non-monolithic builds have been tested.
 find_package(pxr CONFIG REQUIRED)
 
@@ -14,9 +16,14 @@ find_package(pxr CONFIG REQUIRED)
 find_package(MaterialX 1.38.6 REQUIRED HINTS ${pxr_DIR})
 
 # We need to open PNG and JPEG files in order to read the number of channels
-# for shading node creation. OIIO should be provided by the USD installation.
+# for shading node creation. OIIO can be provided by the USD installation,
+# otherwise we fall back to stb_image.
 find_package(OpenImageIO HINTS ${pxr_DIR})
 
+# Optionally support draco. See Finddraco.cmake for more information.
+set(draco_ROOT ${pxr_DIR})
+find_package(draco)
+
 option(GUC_BUILD_EXECUTABLE "Build the guc executable." ON)
 option(GUC_BUILD_USDGLTF "Build the Sdf file format plugin." OFF)
 

README.md

@@ -69,6 +69,7 @@ An example asset conversion is described in the [Structure Mapping](docs/Structu
 Name                                | Status                        
 ------------------------------------|----------
 EXT_meshopt_compression             | ✅ Complete
+KHR_draco_mesh_compression          | ✅ Complete
 KHR_lights_punctual                 | ✅ Partial <sup>1</sup>
 KHR_materials_clearcoat             | ✅ Complete
 KHR_materials_emissive_strength     | ✅ Complete

cmake/Finddraco.cmake

@@ -0,0 +1,32 @@
+#
+# Finds draco and populates following variables:
+#   DRACO_FOUND (draco_FOUND)
+#   DRACO_INCLUDE_DIR
+#   DRACO_LIBRARIES
+#
+# The reason why we ship our custom Find* file is that the draco version
+# that USD uses, 1.3.6, has a broken CMake config file.
+#
+# This also caused trouble for USD, which is why it comes with a custom
+# Find* script similar to this one. However, the script has two issues:
+#   1) It specifies full file names, causing 'libdraco.1.dylib' to not
+#      be found on macOS.
+#   2) It only finds the main draco lib, but not the decoder-specific
+#      lib which we need in guc.
+#
+
+find_path(DRACO_INCLUDE_DIR NAMES "draco/core/draco_version.h")
+
+find_library(DRACO_LIBRARY NAMES draco PATH_SUFFIXES lib)
+find_library(DRACO_DEC_LIBRARY NAMES dracodec PATH_SUFFIXES lib)
+
+set(DRACO_LIBRARIES ${DRACO_LIBRARY} ${DRACO_DEC_LIBRARY})
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(draco
+  REQUIRED_VARS
+    DRACO_INCLUDE_DIR
+    DRACO_DEC_LIBRARY
+    DRACO_LIBRARY
+    DRACO_LIBRARIES
+)

src/libguc/CMakeLists.txt

@@ -62,6 +62,11 @@ else()
   list(APPEND LIBGUC_SHARED_LIBRARIES $<BUILD_INTERFACE:stb_image>)
 endif()
 
+if(draco_FOUND)
+  list(APPEND LIBGUC_DEFINES "GUC_USE_DRACO")
+  list(APPEND LIBGUC_SHARED_LIBRARIES ${DRACO_LIBRARIES})
+endif()
+
 #
 # libguc
 #
@@ -75,10 +80,15 @@ add_library(
 target_link_libraries(libguc PRIVATE ${LIBGUC_SHARED_LIBRARIES})
 
 target_include_directories(libguc
-  PUBLIC $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
-  PUBLIC $<INSTALL_INTERFACE:include>
+  PUBLIC
+    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
+    $<INSTALL_INTERFACE:include>
 )
 
+if(draco_FOUND)
+  target_include_directories(libguc PRIVATE ${DRACO_INCLUDE_DIRS})
+endif()
+
 set_target_properties(
   libguc
   PROPERTIES
@@ -156,6 +166,10 @@ if(GUC_BUILD_USDGLTF)
 
   target_include_directories(usdGlTF PRIVATE "${CMAKE_CURRENT_SOURCE_DIR}/include")
 
+  if(draco_FOUND)
+    target_include_directories(usdGlTF PRIVATE ${DRACO_INCLUDE_DIRS})
+  endif()
+
   target_compile_definitions(
     usdGlTF
     PRIVATE