Sorry, I think I see what you're getting at and I didn't before.  If I
understand it correctly a 'material_map' does not allow for manipulation of the
indices the way 'image_pattern' does.
You can specify a [value texture] format instead of just list textures out 0 to
255.

#declare IPp=
  texture {
    image_pattern { tga "belinda.tga" use_alpha}
    texture_map {
      [0 pigment {rgb <1,0,0>} ] // index 0
      [.5 pigment {rgb <0,1,0>} ] // index 127
      [1 pigment {rgb <0,0,1>} ] // index 255
    } translate -.5 scale 1.5  // transformations
  }

Where as 'material_map' goes like this:

#declare IPm=
texture {
 material_map { tga "belinda.tga"
  texture { pigment {rgb <1,0,0>}} // index 0
  texture { pigment {rgb <0,1,0>}} // index 1
  texture { pigment {rgb <0,0,1>}} // index 2
 }}

That is if I understand any of it right.  You can include image_patterns inside
of image patterns apparently (nesting), material_maps don't seem to be capable
of that.

Bob

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