Wasn't it Christopher James Huff who wrote:

>Alpha maps...I've long wanted transparency separated from color. Making 
>transparency controllable by a pattern or function would be incredibly 
>powerful.

It's already achievable in POV 3.5. This is a texture I've used for
importing transparency maps from Poser. "transmap.jpg" is used to
control the transparency and "texture.jpg" is used to control the
colour. Obviously, the two image_maps could be replaced by any pattern
or function.

texture {
  pigment_pattern {image_map {jpeg "transmap.jpg" interpolate 2}}
  texture_map {
     [0 pigment {rgbt <0,0,0,1>}]
     [1 pigment {image_map {jpeg "texture.jpg" interpolate 2}}]
  }      
}

I guess the same technique could be used to manage specularity mapping,
but I've not tried it.

-- 
Mike Williams
Gentleman of Leisure

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