The above textures were created using tebVoronoi.sl with RIB files such as voronoi.rib. The shader randomly positions feature points in 3D space and calculates the nth nearest feature points. The four textures shown above are based off the distance between the point being shaded and the first nearest, second nearest, third nearest and fourth nearest feature points respectively. Notice how the first texture has the look of a Voronoi diagram. The second texture can sometimes show medial-axis based highlights.
The tebVoronoi.sl shader is based off of Steven Worley's SIGGRAPH 96 article: A Cellular Texture Basis Function. An accelerated PRMan 3.8 DSO version of the cell basis code works with PRMan's 3.8 DSO Shader Operation feature and more than doubles the performance.
This texture shows what a cell basis of F2-F1 looks like. The potential for a cell basis
to look like gravel, a stone bed, or reptile skin can be seen in this simple function of
a cell basis. Refer to tebVoronoi.sl and
tex1.rib. Use the DSO version
tex1DSO.rib with the
PRMan 3.8 DSO version of the shader to get a noticeable
performance boost usually around double the speed.
For the torus image shown, a shader with a filterstep to transition between
the red tile color and the gray mortar was used.