OpenSubdiv is a set of open source libraries that implement high performance subdivision surface (subdiv) evaluation on massively parallel CPU and GPU architectures. This codepath is optimized for drawing deforming subdivs with static topology at interactive framerates. The resulting limit surface matches Pixar's Renderman to numerical precision.
OpenSubdiv is covered by the [Microsoft Public License](http://www.microsoft.com/en-us/openness/licenses.aspx#MPL), and is free to use for commercial or non-commercial use. This is the same code that Pixar uses internally for animated film production. Our intent is to encourage high performance accurate subdiv drawing by giving away the "good stuff".
The current version is "Release Candidate 1.0" (12/05/2012) and we hope to have "Release 1.0" ready by February 2013. Feel free to use it and let us know what you think.
- [Feature Adaptive GPU Rendering of Catmull-Clark Surfaces](http://research.microsoft.com/en-us/um/people/cloop/tog2012.pdf).
- New API architecture : we are planning to lock on to this new framework as the basis for backward compatibility, which we will enforce from Release 1.0 onward. Subsequent releases of OpenSubdiv should not break client code.
We have adopted the git flow branching model. It is not necessary to use the git-flow extensions, though you may find them useful! But it will be helpful to read about the git flow branching model in order to understand the organization of branches and tags that you will find in the repository.
Cmake will adapt the build based on which dependencies have been successfully discovered and will disable certain features and code examples accordingly.
OpenSubdiv may also be used for mobile app development.
Support for the CPU and GPU APIs used by OpenSubdiv is more limited on today's mobile operating systems. For example, the most widely support graphics API is OpenGL ES 2.0 which doesn't yet provide the support for tessellation shaders needed to fully implement GPU accellerated Feature Adaptive Subdivision.
OpenSubdiv can still be used to compute uniform refinement of subdivision surfaces for display on these platforms, realizing all of the benefits of a consistent interpretation of subdivision schemes and tags.
The easiest way to get started using OpenSubdiv for mobile is to use CMake's support for cross-compiling:
In order for us to accept code submissions (merge git pull-requests), contributors need to sign the "Contributor License Agreement" (found in the code repository or [here](https://github.com/PixarAnimationStudios/OpenSubdiv/blob/master/OpenSubdivCLA.pdf)) and you can either email or fax it to Pixar.
There are many things we'd love to do to improve support for subdivs but don't have the resources to. In particular, we would welcome contributions for the following items :
* John Lasseter loves looking at film assets in progress on an iPad. If anyone were to get this working on iOS he'd be looking at your code, and the apple geeks in all of us would smile.
* The precomputation step with hbr can be slow. Does anyone have thoughts on higher performance with topology rich data structures needed for feature adaptive subdivision? Maybe a class that packs adjacency into blocks of indices efficiently, or supports multithreading ?
