Guerilla Render includes a Ptex support in version 0.13.
It supports Catmull Clark subdivision surfaces (any kind of polygons),
triangle meshes and quad meshes.
It works like with any other textures, except that the "st" input is
ignored.
The Ptex textures are also visible in the OpenGL viewports, but in low
quality.
Cyril
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http://www.guerillarender.com