Ptex is a new format for texture maps. With Ptex there is no need to generate texture coordinates. It performs high quality filtering between polygons/patches, has subdivision support, and is open source.
Ptex allows you to apply separate textures for each face of a subdivisions or polygon mesh, and can store thousands of texture images in a single file. Houdini has support for Ptex files in a few places.
The environment function only recognizes Houdini filters and maps these to the ptex filters. The current mapping of Houdini filters to Ptex filters is:
The gptex program allows you to take individual maps for every polygon in your model and generate a .ptx texture for the model.
gptex [-f maplist] geofile ptexfile [mapfiles...]
Create a Ptex map for a geometry file and all the matching texture maps. Texture maps can either be read from a file (using the -f option) or specified on the command line.
Text file containing a texture map per face
All maps must have power of 2 resolution. All maps must have the same number of color channels. All maps must have the same storage type. All polygons must be quadrilaterals.
% gptex box.geo box.ptx face0.rat face0.exr face1.pic face2.tif face3.pic face4.pic face5.pic
Will generate the box.ptx texture file from the box and the corresponding 6 texture maps.
isixpack can generate .ptx files for reflection/environment maps. These maps provide better filtering when there’s lots of blurring when compared to using .rat files.
There are new VOPs to access ptex files, such as ptexture.
3D coat is a 3rd party paint package which has ptex support, eliminating the need for gptex.