Ptex

Ptex 3.10

The Ptex texture format provides a convenient way of texture mapping on non-parametric surface geometry like arbitrary triangle meshes. When used in conjunction with subdivision, the texture information can be painted on any location of the mesh in desired detail. The resulting data stored in a ptex file is able to keep the relation between individual mesh faces and the assigned texture without the need for a 2D parametric coordinate layout like traditional textures. On the other hand, a specific ptex texture is more closely related to the surface geometry it was created for.

Since the shader is utilizing third-party implementation that is delivered as a separate dynamic runtime the shader comes in its own binary package, which must be loaded into the mental ray rendering software before use. A .mi scene file may use the statements

link "ptex.so"
$include <ptex.mi>

Ptex Texture Lookup

Lookup of per-face texture data from a ptex file for mapping on ccmesh subdivision surface geometry. A ptex file stores texture information on a per face basis rather than by spatial 2D coordinates. Thus, it allows to assign colors to the mesh surface without the need of a 2D parametric UV space. On the other hand, a specific ptex texture is more closely related to the surface geometry it was painted for.

mib_ptex_lookup 3.10

shader color "mib_ptex_lookup" (
    string          "filename",
    scalar          "width",
    scalar          "blur",
    integer         "filtertype",
    boolean         "interpolate_level",
    scalar          "filter_sharpness")

filename

the .ptx file. May reside in any of the mental ray texture search path directories.

width

scale factor for filter width.

blur

blur amount in the range [0…1] in addition to filter width.

filtertype

0 - Point-sampled (no filtering)
1 - Bi-linear interpolation
2 - Box filter
3 - Gaussian filter
4 - General bi-cubic filter (uses sharpness option)
5 - BSpline (equivalent to bi-cubic w/ sharpness=0)
6 - Catmull-Rom (equivalent to bi-cubic w/ sharpness=1)
7 - Mitchell (equivalent to bi-cubic w/ sharpness=2/3)

interpolate_level

enables interpolation between mipmap levels.

filter_sharpness

sharpness value for general bi-cubic filter only.