glTF exporter: Draco compression

Note that blender must use this patch to use Draco compression: https://developer.blender.org/D4501
Currenlty, this patch is not merged yet into master

io_scene_gltf2/__init__.py

@@ -14,7 +14,7 @@
 
 bl_info = {
     'name': 'glTF 2.0 format',
-    'author': 'Julien Duroure, Norbert Nopper, Urs Hanselmann, Moritz Becher, Benjamin Schmithüsen',
+    'author': 'Julien Duroure, Norbert Nopper, Urs Hanselmann, Moritz Becher, Benjamin Schmithüsen, Jim Eckerlein',
     "version": (0, 0, 1),
     'blender': (2, 80, 0),
     'location': 'File > Import-Export',
@@ -26,6 +26,7 @@ bl_info = {
     'category': 'Import-Export',
 }
 
+
 #
 # Script reloading (if the user calls 'Reload Scripts' from Blender)
 #
@@ -33,6 +34,7 @@ bl_info = {
 def reload_package(module_dict_main):
     import importlib
     from pathlib import Path
+
     def reload_package_recursive(current_dir, module_dict):
         for path in current_dir.iterdir():
             if "__init__" in str(path) or path.stem not in module_dict:
@@ -56,6 +58,7 @@ from bpy.props import (StringProperty,
                        IntProperty)
 from bpy.types import Operator
 from bpy_extras.io_utils import ImportHelper, ExportHelper
+from io_scene_gltf2.io.exp import gltf2_io_draco_compression_extension
 
 
 #
@@ -64,9 +67,11 @@ from bpy_extras.io_utils import ImportHelper, ExportHelper
 
 
 class ExportGLTF2_Base:
-
     # TODO: refactor to avoid boilerplate
 
+    def __init__(self):
+        self.is_draco_available = gltf2_io_draco_compression_extension.dll_exists()
+
     bl_options = {'UNDO', 'PRESET'}
 
     export_format: EnumProperty(
@@ -114,6 +119,44 @@ class ExportGLTF2_Base:
         default=True
     )
 
+    export_draco_mesh_compression_enable: BoolProperty(
+        name='Draco mesh compression',
+        description='Compress mesh using Draco',
+        default=False
+    )
+
+    export_draco_mesh_compression_level: IntProperty(
+        name='Compression level',
+        description='Compression level (0 = most speed, 6 = most compression, higher values currently not supported)',
+        default=6,
+        min=0,
+        max=6
+    )
+
+    export_draco_position_quantization: IntProperty(
+        name='Position quantization bits',
+        description='Quantization bits for position values (0 = no quantization)',
+        default=14,
+        min=0,
+        max=30
+    )
+
+    export_draco_normal_quantization: IntProperty(
+        name='Normal quantization bits',
+        description='Quantization bits for normal values (0 = no quantization)',
+        default=10,
+        min=0,
+        max=30
+    )
+
+    export_draco_texcoord_quantization: IntProperty(
+        name='Texcoord quantization bits',
+        description='Quantization bits for texture coordinate values (0 = no quantization)',
+        default=12,
+        min=0,
+        max=30
+    )
+
     export_tangents: BoolProperty(
         name='Tangents',
         description='Export vertex tangents with meshes',
@@ -309,11 +352,21 @@ class ExportGLTF2_Base:
         export_settings['gltf_texcoords'] = self.export_texcoords
         export_settings['gltf_normals'] = self.export_normals
         export_settings['gltf_tangents'] = self.export_tangents and self.export_normals
+
+        if self.is_draco_available:
+            export_settings['gltf_draco_mesh_compression'] = self.export_draco_mesh_compression_enable
+            export_settings['gltf_draco_mesh_compression_level'] = self.export_draco_mesh_compression_level
+            export_settings['gltf_draco_position_quantization'] = self.export_draco_position_quantization
+            export_settings['gltf_draco_normal_quantization'] = self.export_draco_normal_quantization
+            export_settings['gltf_draco_texcoord_quantization'] = self.export_draco_texcoord_quantization
+        else:
+            export_settings['gltf_draco_mesh_compression'] = False
+
         export_settings['gltf_materials'] = self.export_materials
         export_settings['gltf_colors'] = self.export_colors
         export_settings['gltf_cameras'] = self.export_cameras
         export_settings['gltf_selected'] = self.export_selected
-        export_settings['gltf_layers'] = True #self.export_layers
+        export_settings['gltf_layers'] = True  # self.export_layers
         export_settings['gltf_extras'] = self.export_extras
         export_settings['gltf_yup'] = self.export_yup
         export_settings['gltf_apply'] = self.export_apply
@@ -385,6 +438,17 @@ class ExportGLTF2_Base:
         col.prop(self, 'export_colors')
         col.prop(self, 'export_materials')
 
+        # Add Draco compression option only if the DLL could be found.
+        if self.is_draco_available:
+            col.prop(self, 'export_draco_mesh_compression_enable')
+
+            # Display options when Draco compression is enabled.
+            if self.export_draco_mesh_compression_enable:
+                col.prop(self, 'export_draco_mesh_compression_level')
+                col.prop(self, 'export_draco_position_quantization')
+                col.prop(self, 'export_draco_normal_quantization')
+                col.prop(self, 'export_draco_texcoord_quantization')
+
     def draw_object_settings(self):
         col = self.layout.box().column()
         col.prop(self, 'export_cameras')

io_scene_gltf2/blender/exp/gltf2_blender_export.py

@@ -23,6 +23,7 @@ from io_scene_gltf2.blender.exp import gltf2_blender_gather
 from io_scene_gltf2.blender.exp.gltf2_blender_gltf2_exporter import GlTF2Exporter
 from io_scene_gltf2.io.com.gltf2_io_debug import print_console, print_newline
 from io_scene_gltf2.io.exp import gltf2_io_export
+from io_scene_gltf2.io.exp import gltf2_io_draco_compression_extension
 
 
 def save(context, export_settings):
@@ -66,6 +67,11 @@ def __get_copyright(export_settings):
 
 def __gather_gltf(exporter, export_settings):
     scenes, animations = gltf2_blender_gather.gather_gltf2(export_settings)
+
+    if export_settings['gltf_draco_mesh_compression']:
+        gltf2_io_draco_compression_extension.compress_scene_primitives(scenes, export_settings)
+        exporter.add_draco_extension()
+
     for scene in scenes:
         exporter.add_scene(scene)
     for animation in animations:

io_scene_gltf2/blender/exp/gltf2_blender_gltf2_exporter.py

@@ -135,6 +135,15 @@ class GlTF2Exporter:
         if is_glb:
             return self.__buffer.to_bytes()
 
+    def add_draco_extension(self):
+        """
+        Register Draco extension as *used* and *required*.
+
+        :return:
+        """
+        self.__gltf.extensions_required.append('KHR_draco_mesh_compression')
+        self.__gltf.extensions_used.append('KHR_draco_mesh_compression')
+
     def finalize_images(self, output_path):
         """
         Write all images.

io_scene_gltf2/io/exp/gltf2_io_draco_compression_extension.py

+import bpy
+import sys
+from ctypes import *
+from pathlib import Path
+
+from io_scene_gltf2.io.exp.gltf2_io_binary_data import BinaryData
+
+
+def dll_path() -> Path:
+    """
+    Get the DLL path depending on the underlying platform.
+    :return: DLL path.
+    """
+    lib_name = 'extern_draco'
+    blender_root = Path(bpy.app.binary_path).parent
+    python_lib = Path('2.80/python/lib')
+    paths = {
+        'win32': blender_root/python_lib/'site-packages'/'{}.dll'.format(lib_name),
+        'linux': blender_root/python_lib/'python3.7'/'site-packages'/'lib{}.so'.format(lib_name),
+        'darwin': blender_root.parent/'Resources'/python_lib/'python3.7'/'site-packages'/'lib{}.dylib'.format(lib_name)
+    }
+
+    path = paths.get(sys.platform)
+    return path if path is not None else ''
+
+
+def dll_exists() -> bool:
+    """
+    Checks whether the DLL path exists.
+    :return: True if the DLL exists.
+    """
+    exists = dll_path().exists()
+    print("'{}' ".format(dll_path().absolute()) + ("exists, draco mesh compression is available" if exists else
+                                                   "does not exist, draco mesh compression not available"))
+    return exists
+
+
+def compress_scene_primitives(scenes, export_settings):
+    """
+    Handles draco compression.
+    Invoked after data has been gathered, but before scenes get traversed.
+    Moves position, normal and texture coordinate attributes into a Draco compressed buffer.
+    """
+
+    # Load DLL and setup function signatures.
+    # Nearly all functions take the compressor as the first argument.
+    dll = cdll.LoadLibrary(str(dll_path().resolve()))
+
+    dll.createCompressor.restype = c_void_p
+    dll.createCompressor.argtypes = []
+
+    dll.setCompressionLevel.restype = None
+    dll.setCompressionLevel.argtypes = [c_void_p, c_uint32]
+
+    dll.setPositionQuantizationBits.restype = None
+    dll.setPositionQuantizationBits.argtypes = [c_void_p, c_uint32]
+
+    dll.setNormalQuantizationBits.restype = None
+    dll.setNormalQuantizationBits.argtypes = [c_void_p, c_uint32]
+
+    dll.setTexCoordQuantizationBits.restype = None
+    dll.setTexCoordQuantizationBits.argtypes = [c_void_p, c_uint32]
+
+    dll.compress.restype = c_bool
+    dll.compress.argtypes = [c_void_p]
+
+    dll.compressedSize.restype = c_uint64
+    dll.compressedSize.argtypes = [c_void_p]
+
+    dll.disposeCompressor.restype = None
+    dll.disposeCompressor.argtypes = [c_void_p]
+
+    dll.setFaces.restype = None
+    dll.setFaces.argtypes = [c_void_p, c_uint32, c_uint32, c_void_p]
+
+    dll.addPositionAttribute.restype = None
+    dll.addPositionAttribute.argtypes = [c_void_p, c_uint32, c_char_p]
+
+    dll.addNormalAttribute.restype = None
+    dll.addNormalAttribute.argtypes = [c_void_p, c_uint32, c_char_p]
+
+    dll.addTexCoordAttribute.restype = None
+    dll.addTexCoordAttribute.argtypes = [c_void_p, c_uint32, c_char_p]
+
+    dll.copyToBytes.restype = None
+    dll.copyToBytes.argtypes = [c_void_p, c_char_p]
+
+    dll.getTexCoordAttributeIdCount.restype = c_uint32
+    dll.getTexCoordAttributeIdCount.argtypes = [c_void_p]
+
+    dll.getTexCoordAttributeId.restype = c_uint32
+    dll.getTexCoordAttributeId.argtypes = [c_void_p, c_uint32]
+
+    dll.getPositionAttributeId.restype = c_uint32
+    dll.getPositionAttributeId.argtypes = [c_void_p]
+
+    dll.getNormalAttributeId.restype = c_uint32
+    dll.getNormalAttributeId.argtypes = [c_void_p]
+
+    dll.setCompressionLevel.restype = None
+    dll.setCompressionLevel.argtypes = [c_void_p, c_uint32]
+
+    dll.setPositionQuantizationBits.restype = None
+    dll.setPositionQuantizationBits.argtypes = [c_void_p, c_uint32]
+
+    dll.setNormalQuantizationBits.restype = None
+    dll.setNormalQuantizationBits.argtypes = [c_void_p, c_uint32]
+
+    dll.setTexCoordQuantizationBits.restype = None
+    dll.setTexCoordQuantizationBits.argtypes = [c_void_p, c_uint32]
+
+    for scene in scenes:
+        for node in scene.nodes:
+            __traverse_node(node, dll, export_settings)
+
+
+def __traverse_node(node, dll, export_settings):
+    if not (node.mesh is None):
+        print("Compressing mesh " + node.name)
+        for primitive in node.mesh.primitives:
+            __compress_primitive(primitive, dll, export_settings)
+
+    if not (node.children is None):
+        for child in node.children:
+            __traverse_node(child, dll, export_settings)
+
+
+def __compress_primitive(primitive, dll, export_settings):
+    attributes = primitive.attributes
+
+    # Begin mesh.
+    compressor = dll.createCompressor()
+
+    # Process position attributes.
+    dll.addPositionAttribute(compressor, attributes['POSITION'].count, attributes['POSITION'].buffer_view.data)
+
+    # Process normal attributes.
+    dll.addNormalAttribute(compressor, attributes['NORMAL'].count, attributes['NORMAL'].buffer_view.data)
+
+    # Process texture coordinate attributes.
+    for attribute in [attributes[attr] for attr in attributes if attr.startswith('TEXCOORD_')]:
+        dll.addTexCoordAttribute(compressor, attribute.count, attribute.buffer_view.data)
+
+    # Process faces.
+    index_byte_length = {
+        'Byte': 1,
+        'UnsignedByte': 1,
+        'Short': 2,
+        'UnsignedShort': 2,
+        'UnsignedInt': 4,
+    }
+    indices = primitive.indices
+    dll.setFaces(compressor, indices.count, index_byte_length[indices.component_type.name], indices.buffer_view.data)
+    indices.buffer_view = None
+
+    # Set compression parameters.
+    dll.setCompressionLevel(compressor, export_settings['gltf_draco_mesh_compression_level'])
+    dll.setPositionQuantizationBits(compressor, export_settings['gltf_draco_position_quantization'])
+    dll.setNormalQuantizationBits(compressor, export_settings['gltf_draco_normal_quantization'])
+    dll.setTexCoordQuantizationBits(compressor, export_settings['gltf_draco_texcoord_quantization'])
+
+    # After all point and connectivity data has been written to the compressor,
+    # it can finally be compressed.
+    if dll.compress(compressor):
+
+        # Compression was successfull.
+        # Move compressed data into a bytes object,
+        # which is referenced by a 'gltf2_io_binary_data.BinaryData':
+        #
+        # "KHR_draco_mesh_compression": {
+        #     ....
+        #     "buffer_view": Compressed data inside a 'gltf2_io_binary_data.BinaryData'.
+        # }
+
+        # Query size necessary to hold all the compressed data.
+        compression_size = dll.compressedSize(compressor)
+
+        # Allocate byte buffer and write compressed data to it.
+        compressed_data = bytes(compression_size)
+        dll.copyToBytes(compressor, compressed_data)
+
+        if primitive.extensions is None:
+            primitive.extensions = {}
+
+        tex_coord_ids = {}
+        for id in range(0, dll.getTexCoordAttributeIdCount(compressor)):
+            tex_coord_ids["TEXCOORD_" + str(id)] = dll.getTexCoordAttributeId(compressor, id)
+
+        # Register draco compression extension into primitive.
+        primitive.extensions["KHR_draco_mesh_compression"] = {
+            'bufferView': BinaryData(compressed_data),
+            'attributes': {
+                'POSITION': dll.getPositionAttributeId(compressor),
+                'NORMAL': dll.getNormalAttributeId(compressor),
+                **tex_coord_ids,
+            }
+        }
+
+        # Set to triangle list mode.
+        primitive.mode = 4
+
+        # Remove buffers from attribute, since the data now resides inside the compressed Draco buffer.
+        attributes['POSITION'].buffer_view = None
+        attributes['NORMAL'].buffer_view = None
+        for attribute in [attributes[attr] for attr in attributes if attr.startswith('TEXCOORD_')]:
+            attribute.buffer_view = None
+
+    # Afterwards, the compressor can be released.
+    dll.disposeCompressor(compressor)
+
+    pass
+