Description

Draco is used to compress and decompress 3d geometry data and point clouds. 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.

Draco is released as C++ source code that can compress and decompress 3d geometry data and point clouds. The package also contains Javascript decoders for the encoded data.

Note: This is not an official Google product.

Building

For all the platforms first you need to generate the project files, then you need to compile the examples.

CMake Basics

To generate project/make files for the default toolchain on your system simply run cmake in the root of the Draco repo:

$ cmake .

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 the -G parameter is added to the cmake command line. 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.

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

$ cmake . -G Xcode

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

$ cmake . -G "Visual Studio 14 2015"

To generate 64-bit Windows Visual Studio 2015 projects:

$ cmake . "Visual Studio 14 2015 Win64"

CMake Makefiles: 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 build flags containing neither optimization nor debug flags:

$ cmake .

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

$ cmake . -DCMAKE_BUILD_TYPE=release

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

$ cmake . -DCMAKE_BUILD_TYPE=relwithdebinfo

And your standard debug build will be produced using:

$ cmake . -DCMAKE_BUILD_TYPE=debug

Android Studio Project Integration

To include Draco in an existing or new Android Studio project it simply needs to be referenced 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} )
   

Examples

Commandline Applications

The default target create 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 the 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 parameters 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.

E.g. ./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 on 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 parameter turns on/off different compression features. In general the highest setting, 10, will have the worst compression ratio but best decompression speed. And 0 will have the best compression ratio, but worst decompression speed.

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. E.g.:

$ ./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

Javascript Decoder

The Javascript decoder is located in javascript/draco_decoder.js. The Javascript decoder can currently only decode mesh geometry. In order to use the decoder you must create DecoderBuffer and WebIDLWrapper objects. Set the encoded data in the DecoderBuffer. Then call DecodeMeshFromBuffer(), which will return a Mesh object. E.g.

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

var wrapper = new WebIDLWrapper();
var outputMesh = wrapper.DecodeMeshFromBuffer(buffer);

destroy(outputMesh);
destroy(wrapper);
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

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

Support

For questions/comments please email draco-3d-discuss@googlegroups.com