CCGSubSurf - Catmull-Clark Gridding Subdivision Surface Library
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CCGSubSurf is a public domain library for working with Catmull-Clark subdivision
surfaces. It is based on a novel algorithm for computing the subdivision surface
that I have developed and refined over several years. Some details of the
algorithm are available below and I hope to provide a detailed article at some
point. For the time being the source is the definitive reference.

Features
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 * Easy-to-use: The library has been designed to make integration into existing
   3D modelling applications as simple as possible without sacrificing
   functionality or performance.

 * Incremental: CCGSubSurf uses an incremental algorithm to only recalculate the
   portions of the subsurf that change in response to edits. For dense meshes
   this gives a potentially unbounded improvement in interactivity.

 * Lightweight: Efforts have been made to keep the memory footprint of the
   subdivision data structures as small as possible. For high levels of
   subdivision the memory use is close to minimal (although supporting
   incremental recalculation does have a certain cost).

 * Fast: Even disregarding the speed improvement from incremental calculation
   the library is still very fast, especially at higher subdivision
   levels. Although primarily intended for interactive (editing) applications,
   it is fast enough to be a viable alternative for applications that merely
   need to compute a subdivided surface.

Missing Features
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 * Creasing: There is currently no support for creasing. In my mind this is the
   largest problem with the library as stands and I hope to correct it sometime
   in the future.

 * Interactivity Improvements: There is a bit of room for more improvements
   targetted at interactive applications, for example providing hooks for
   progress reporting or allowing the subdivision to be aborted and then
   restarted (after mutating the mesh) in order to support zero-lag editing.
   Adaptive: The library does not support adaptive subdivision. I believe that I
   can integrate it efficiently into the algorithm but have not spent a
   considerable amount of time or thought on the issue. At the moment it is on
   the wishlist, but since I have qualms about adaptive subdivision in general
   it is not near the top of the list.  Download

Releases
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CCGSubSurf v0.01: An alpha release, just contains the source code and a glut
demo as well as a compiled win32 version of the demo. After integration with
Blender I made a few refinements to the API and added vertex normal calculation,
but these changes have not been merged back yet. There is also no documentation
in this release, although I hope the demo is fairly self-explanatory.