Open Game Engine Exchange (OpenGEX)

The Open Game Engine Exchange (OpenGEX) format is a text-based file format designed to facilitate the transfer of complex scene data between applications such as modeling tools and game engines. The OpenGEX format is built upon the data structure concepts defined by the Open Data Description Language (OpenDDL), a generic language for the storage of arbitrary data in human-readable format.

Download OpenGEX specification, version 2.0 (OpenGEX.2.0.pdf) The specification is also available in print on Amazon.

The OpenGEX format was created because Collada, the open standard that we all hoped would provide a well-supported asset exchange format, has proven to be an unreliable mess. The most common source of problems has been the poor quality of the Collada export plugins available for software such as 3D Studio Max and Maya, and we attribute this to Collada’s over-engineered design and its mutating under-specified format.

Compare OpenGEX, Collada, and glTF

OpenGEX Export Plugins

Official OpenGEX export plugins for 3D Studio Max, Maya, and Blender can be downloaded here. The source code for these plugins is provided under the Creative Commons Attribution-ShareAlike 3.0 Unported License.

The export plugins posted here support the following features:

• Hierarchical scene organization (node trees).
• Factored node transforms where necessary (e.g., splitting into position, rotation, and scale).
• Object instancing (multiple nodes can reference the same object).
• Geometry objects, light objects, and camera objects.
• Multiple materials per mesh with independent binding per instance.
• Multiple vertex colors and texture coordinate sets per mesh.
• Skinned meshes (skeleton, bind-pose transforms, bone influence weighting data).
• Morphed meshes (also known as blend shapes or shape keys).
• Keyframe animation for all node transforms and morph weights.
• Linear, Bézier, and TCB animation curves.
• Material colors and textures (diffuse, specular, normal, emission, opacity, transparency).
• Texture coordinate transforms.

3D Studio Max

OpenGEX export plugin version 2.0
(Last updated 29-Jan-2017)

• Download export plugin for 3D Studio Max 2014. To install, drag the file OpenGex.dle into the 3D Studio Max plugins directory.
• Download the source code for the Max plugin. The plugin can be built from source with Visual Studio 2013.

This plugin may need to be recompiled from source for later versions of 3D Studio Max.

Maya

OpenGEX export plugin version 2.0
(Last updated 29-Jan-2017)

• Download export plugin for Maya 2014. To install, drag the file OpenGex.mll into the Maya bin/plug-ins directory.
• Download the source code for the Maya plugin. The plugin can be built from source with Visual Studio 2013.

This plugin may need to be recompiled from source for later versions of Maya.

Blender

Blender export script version 2.0
(Last updated 29-Jan-2017)

• Download export script for Blender 2.72. To install, run Blender, select User Preferences from the File menu, Click the Install from File button, choose the script OpenGex-Blender.py, and finally check the box next to "Import-Export: OpenGEX format (.ogex)".

OpenGEX Import Template

A free OpenGEX 2.0 import template can be downloaded through the following link. See the software license in the source code. This package includes project files for Visual Studio 2017, and the solution file can be found in the OpenGEX-Import/OpenGEX/ directory. This template is essentially the OpenGEX import plugin for the Tombstone Engine with the engine-specific parts stripped out. It reads an OpenGEX file and creates all of the structures necessary to construct a scene, but application-specific processing must be added in the appropriate places to support any other software.

Download OpenGEX Import Template
(Last updated 11-Apr-2017)

Revision History

Version 2.0. 29-Jan-2017

• The "forward" key was added to the Metric structure to specify the forward direction for models such as characters and vehicles.
• The exact calculations necessary for converting between y and z up directions was added to the specification for the Metric structure.
• The "fovx" and "fovy" parameters were added to the CameraObject structure.
• The Open Data Description Language was updated to version 2.0.

Version 1.1.2. 10-Dec-2014

• Expanded the Morph structure to have an optional base property.
• Added explanation of morphing calculations to the description of the MorphWeight structure.

Version 1.1.1. 1-Dec-2014

• Added the MorphWeight structure.
• Revised the usage of the Morph structure.

Version 1.1. 24-Nov-2014

• Added the Extension structure.
• Added the Clip structure.
• Allowed multiple Animation structures with the same clip index inside the same parent structure.
• Expanded the curve kinds accepted by the Value structure to include "constant".
• Expanded the attributes accepted by the Value structure to include "specular_power".
• Expanded the VertexArray structure to allow floating-point data of any bit width.
• Updated OpenDDL support to version 1.1.

Version 1.0.1. 26-Aug-2014

• Fixed math for Bézier time parameter in Track structure.

Version 1.0. 24-Sep-2013

• Initial specification.

Previous Specifications

• Download OpenGEX specification, version 1.1.2 (OpenGEX.1.1.2.pdf)
• Download OpenGEX specification, version 1.0.1 (OpenGEX.1.0.1.pdf)

About

OpenGEX was created by Eric Lengyel and is implemented in the art pipeline of the Tombstone Engine.

The OpenGEX file format is registered with the Internet Assigned Numbers Authority (IANA) as the model/vnd.opengex media type.

Copyright © 2013–2017 by Eric Lengyel

OpenGEX and the images on this page by Eric Lengyel are licensed under a
Creative Commons Attribution-ShareAlike 3.0 Unported License.
Based on a work at http://opengex.org/.