Between five and seven octaves usually works well. Thresh is used to specify a lower bound on the output of the fBm function. Any value lower than thresh is set to zero. If a colormap is named, a 256-entry colormap is read from the named file, and the sample of fBm is scaled by 255 and is used as an index into the colormap. The resulting colormap entry is used to scale the ambient and diffuse components of the object's surface.
H octaves Similar to the fbm texture.
Rather than modifying the color of a surface, this texture acts as a bump map. Gives reflective surfaces a glossy appearance. 1. - glossiness . A value of 1 results in perfect mirror-like reflections, while a value of 0 results in extremely fuzzy reflections. For best results, jittered sampling should be used to render scenes that make use of this texture.