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##OVERVIEW

COLLADA2JSON introduces a JSON format that aims to bridge the gap between COLLADA and WebGL.
As an initiative from the COLLADA Working Group, this project stands in Khronos repository.
Everyone is welcomed to contribute and provide feedback.

This is a work in progress and not an official Khronos-ratified specification.

JSON Format

The JSON format has been designed from the ground up with an eye towards the requirements of WebGL, and is intended to be the final step in a COLLADA to WebGL workflow. COLLADA is an interchange format created to allow information to easily be passed between authoring tools, but is not well suited for use in web or embedded device applications.

The JSON format is actually a hybrid format consisting of two files:

  • A JSON document describing the scene graph and its entities.
  • A separate binary blob containing all large data arrays (indices/vertices).

To satisfy WebGL constraints, the provided tool named COLLADA2JSON performs the following transformations: (Most of these are work in progress)

  • Unify index buffers with unique indices for all vertex attributes. (Known as "deindexing")
  • Split meshes into buffers that do not exceed 65535 indices to satisfy the WebGL's maximum index size of UNSIGNED_SHORT
  • Generate default GLSL shaders from the COLLADA materials.
  • Normalize the "Up" axis of all scenes to allow easy resource sharing.

Using an external binary blob has several advantages:

  • The JSON format references the buffers as opaque typed arrays.
  • The binary format provides opportunities for better data compression.

More details about the format in the wiki

Watch the GitHub issues tracker for updates on the status of these features.

What's provided in this repository:

  • viewer: A sample WebGL viewer (Chrome canary recommanded) that loads and displays a model asynchronously (vertex and index buffers loaded progressivly). The example model contains thousands of independant meshes and buffers (to show progressive loading).
  • converter: Source code for COLLADA2JSON converter based on OpenCOLLADA
  • loaders: Loader utilities for 3rd party WebGL libraries. Currently contains a Three.js loader, with support planned for other popular WebGL frameworks.

Workflow

COLLADA2JSON provides a reliable toolchain based on OpenCOLLADA. Starting from exporter plugins in major authoring tools to COLLADA parsing when converting to JSON, OpenCOLLADA is where all efforts to import/export COLLADA files are centralized.

Viewer setup

git clone https://github.com/KhronosGroup/collada2json.git
cd collada2json
git submodule update --init --recursive
git submodule foreach git pull origin master

Start a web server in collada2json/webgl which contains an index.html page linking to the demos.

Converter build instructions

Windows
  • Install CMake
  • cd collada2json/converter/dae2json
  • cmake CMakeLists.txt

open COLLADA2JSON.sln and build.

Mac OSX
  • Install CMake
  • cd collada2json/converter/dae2json
  • cmake -G Xcode

open COLLADA2JSON.xcodeproj and build, or if you installed xcode command line tools you can also build in the terminal: xcodebuild -target collada2json