"Mick Hazelgrove" <mic### [at] mhazelgrovefsnetcouk> wrote in message
news:3be536c2@news.povray.org...
>
> "JRG" <jrg### [at] hotmailcom> wrote in message
> news:3be53443@news.povray.org...
> > Instead of using a color_map to define transparent and non-transparent
> areas
> > use a texture_map.
>
> I'm using an image map with the transparent areas defined by the alpha
> channal attached to the image map - so I can't really do this.
>
> Mick

JRG and Tony have it right. Finish maps would be useful here but the only two
ways I've discovered to vary the finish across a surface with bitmaps are using
either a material_map or 3.5's image_pattern. Image_pattern is the friendlier of
the two, from both usability and system memory consumption, standpoints.

Just declare your pigment{} (and possibly normal{}) using your image_map and
then declare two textures that use these with different finish statements.
Finally create a grayscale image from your original image_map and use the map
part of the image_pattern statement to control the blend between the two
textures.

For perspective, a material_map would employ basically the same technique only
you would have to pre-declare up to 255 textures differing only in finish
(yech!).

I can't say at the moment whether the alpha will work better in the
image_pattern or is best left in the original image_map, since I haven't tried
that yet.

Good Luck!

Batronyx ^"^

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