Description

Draco is a library for compressing and decompressing 3D geometric meshes and point clouds. It is intended to improve the storage and transmission of 3D graphics.

Draco was designed and built for compression efficiency and speed. The code supports compressing points, connectivity information, texture coordinates, color information, normals, and any other generic attributes associated with geometry. With Draco, applications using 3D graphics can be significantly smaller without compromising visual fidelity. For users, this means apps can now be downloaded faster, 3D graphics in the browser can load quicker, and VR and AR scenes can now be transmitted with a fraction of the bandwidth and rendered quickly.

Draco is released as C++ source code that can be used to compress 3D graphics as well as C++ and Javascript decoders for the encoded data.

Contents

• Building
  • CMake Basics
  • Mac OS X
  • Windows
  • CMake Build Configuration
    • Debugging and Optimization
    • Googletest Integration
    • Javascript Decoder
  • Android Studio Project Integration
• Usage
  • Command Line Applications
  • Encoding Tool
  • Encoding Point Clouds
  • Decoding Tool
  • C++ Decoder API
  • Javascript Decoder
  • Javascript Decoder Performance
  • three.js Renderer Example
• Support
• License
• References

Building

For all platforms, you must first generate the project/make files and then compile the examples.

CMake Basics

To generate project/make files for the default toolchain on your system, run cmake from a directory where you would like to generate build files, and pass it the path to your Draco repository.

$ cmake path/to/draco

On Windows, the above command will produce Visual Studio project files for the newest Visual Studio detected on the system. On Mac OS X and Linux systems, the above command will produce a makefile.

To control what types of projects are generated, add the -G parameter to the cmake command. This argument must be followed by the name of a generator. Running cmake with the --help argument will list the available generators for your system.

Mac OS X

On Mac OS X, run the following command to generate Xcode projects:

$ cmake path/to/draco -G Xcode

Windows

On a Windows box you would run the following command to generate Visual Studio 2015 projects:

C:\Users\nobody> cmake path/to/draco -G "Visual Studio 14 2015"

To generate 64-bit Windows Visual Studio 2015 projects:

C:\Users\nobody> cmake path/to/draco "Visual Studio 14 2015 Win64"

CMake Build Configuration

Debugging and Optimization

Unlike Visual Studio and Xcode projects, the build configuration for make builds is controlled when you run cmake. The following examples demonstrate various build configurations.

Omitting the build type produces makefiles that use release build flags by default:

$ cmake path/to/draco

A makefile using release (optimized) flags is produced like this:

$ cmake path/to/draco -DCMAKE_BUILD_TYPE=release

A release build with debug info can be produced as well:

$ cmake path/to/draco -DCMAKE_BUILD_TYPE=relwithdebinfo

And your standard debug build will be produced using:

$ cmake path/to/draco -DCMAKE_BUILD_TYPE=debug

Googletest Integration

Draco includes testing support built using Googletest. To enable Googletest unit test support the ENABLE_TESTS cmake variable must be turned on at cmake generation time:

$ cmake path/to/draco -DENABLE_TESTS=ON

When cmake is used as shown in the above example the Draco cmake file assumes that the Googletest source directory is a sibling of the Draco repository. To change the location to something else use the GTEST_SOURCE_DIR cmake variable:

$ cmake path/to/draco -DENABLE_TESTS=ON -DGTEST_SOURCE_DIR=path/to/googletest

To run the tests just execute draco_tests from your toolchain's build output directory.

Javascript Decoder

The javascript decoder can be built using the existing cmake build file by passing the path the Emscripten's cmake toolchain file at cmake generation time in the CMAKE_TOOLCHAIN_FILE variable. In addition, the EMSCRIPTEN environment variable must be set to the local path of the parent directory of the Emscripten tools directory.

# Make the path to emscripten available to cmake.
$ export EMSCRIPTEN=/path/to/emscripten/tools/parent

# Emscripten.cmake can be found within your Emscripten installation directory,
# it should be the subdir: cmake/Modules/Platform/Emscripten.cmake
$ cmake path/to/draco -DCMAKE_TOOLCHAIN_FILE=/path/to/Emscripten.cmake

Android Studio Project Integration

To include Draco in an existing or new Android Studio project, reference it from the cmake file of an existing native project that has a minimum SDK version of 18 or higher. To add Draco to your project:

1. Add the following somewhere within the CMakeLists.txt for your project before the add_library() for your project's native-lib:

   # Note "/path/to/draco" must be changed to the path where you have cloned
   # the Draco sources.
   
   add_subdirectory(/path/to/draco
                    ${CMAKE_BINARY_DIR}/draco_build)
   include_directories("${CMAKE_BINARY_DIR}" /path/to/draco)

2. Add the library target "draco" to the target_link_libraries() call for your project's native-lib. The target_link_libraries() call for an empty activity native project looks like this after the addition of Draco:

   target_link_libraries( # Specifies the target library.
                          native-lib
   
                          # Tells cmake this build depends on libdraco.
                          draco
   
                          # Links the target library to the log library
                          # included in the NDK.
                          ${log-lib} )

Usage

Command Line Applications

The default target created from the build files will be the draco_encoder and draco_decoder command line applications. For both applications, if you run them without any arguments or -h, the applications will output usage and options.

Encoding Tool

draco_encoder will read OBJ or PLY files as input, and output Draco-encoded files. We have included Stanford's Bunny mesh for testing. The basic command line looks like this:

./draco_encoder -i testdata/bun_zipper.ply -o out.drc

A value of 0 for the quantization parameter will not perform any quantization on the specified attribute. Any value other than 0 will quantize the input values for the specified attribute to that number of bits. For example:

./draco_encoder -i testdata/bun_zipper.ply -o out.drc -qp 14

will quantize the positions to 14 bits (default for the position coordinates).

In general, the more you quantize your attributes the better compression rate you will get. It is up to your project to decide how much deviation it will tolerate. In general, most projects can set quantizations values of about 14 without any noticeable difference in quality.

The compression level (-cl) parameter turns on/off different compression features.

./draco_encoder -i testdata/bun_zipper.ply -o out.drc -cl 8

In general, the highest setting, 10, will have the most compression but worst decompression speed. 0 will have the least compression, but best decompression speed. The default setting is 5.

Encoding Point Clouds

You can encode point cloud data with draco_encoder by specifying the point_cloud parameter. If you specify the point_cloud parameter with a mesh input file, draco_encoder will ignore the connectivity data and encode the positions from the mesh file.

./draco_encoder -point_cloud -i testdata/bun_zipper.ply -o out.drc

This command line will encode the mesh input as a point cloud, even though the input might not produce compression that is representative of other point clouds. Specifically, one can expect much better compression rates for larger and denser point clouds.

Decoding Tool

draco_decoder will read Draco files as input, and output OBJ or PLY files. The basic command line looks like this:

./draco_decoder -i in.drc -o out.obj

C++ Decoder API

If you'd like to add decoding to your applications you will need to include the draco_dec library. In order to use the Draco decoder you need to initialize a DecoderBuffer with the compressed data. Then call DecodeMeshFromBuffer() to return a decoded mesh object or call DecodePointCloudFromBuffer() to return a decoded PointCloud object. For example:

draco::DecoderBuffer buffer;
buffer.Init(data.data(), data.size());

const draco::EncodedGeometryType geom_type =
    draco::GetEncodedGeometryType(&buffer);
if (geom_type == draco::TRIANGULAR_MESH) {
  unique_ptr<draco::Mesh> mesh = draco::DecodeMeshFromBuffer(&buffer);
} else if (geom_type == draco::POINT_CLOUD) {
  unique_ptr<draco::PointCloud> pc = draco::DecodePointCloudFromBuffer(&buffer);
}

Please see mesh/mesh.h for the full Mesh class interface and point_cloud/point_cloud.h for the full PointCloud class interface.

Javascript Decoder

The Javascript decoder is located in javascript/draco_decoder.js. The Javascript decoder can decode mesh and point cloud. In order to use the decoder you must first create DecoderBuffer and WebIDLWrapper objects. Set the encoded data in the DecoderBuffer. Then call GetEncodedGeometryType() to identify the type of geometry, e.g. mesh or point cloud. Then call either DecodeMeshFromBuffer() or DecodePointCloudFromBuffer(), which will return a Mesh object or a point cloud. For example:

const buffer = new Module.DecoderBuffer();
buffer.Init(encFileData, encFileData.length);

const wrapper = new Module.WebIDLWrapper();
const geometryType = wrapper.GetEncodedGeometryType(buffer);
let outputGeometry;
if (geometryType == Module.TRIANGULAR_MESH) {
  outputGeometry = wrapper.DecodeMeshFromBuffer(buffer);
} else {
  outputGeometry = wrapper.DecodePointCloudFromBuffer(buffer);
}

Module.destroy(outputGeometry);
Module.destroy(wrapper);
Module.destroy(buffer);

Please see javascript/emscripten/draco_web.idl for the full API.

Javascript Decoder Performance

The Javascript decoder is built with dynamic memory. This will let the decoder work with all of the compressed data. But this option is not the fastest. Pre-allocating the memory sees about a 2x decoder speed improvement. If you know all of your project's memory requirements, you can turn on static memory by changing Makefile.emcc and running make -f Makefile.emcc.

three.js Renderer Example

Here's an example of a geometric compressed with Draco loaded via a Javascript decoder using the three.js renderer.

Please see the javascript/example/README file for more information.

Support

For questions/comments please email [email protected]

If you have found an error in this library, please file an issue at https://github.com/google/draco/issues

Patches are encouraged, and may be submitted by forking this project and submitting a pull request through GitHub. See CONTRIBUTING for more detail.

License

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

References

Bunny model from Stanford's graphic department https://graphics.stanford.edu/data/3Dscanrep/