There's an example of it's use in the Patterns.htm file which is packaged with
MegaPOV patch.
It's basically a texture_map using a image as guidelines for the texture index.

Bob

"Fabian Brau" <fab### [at] umhacbe> wrote in message
news:388F30B7.B024EBDD@umh.ac.be...
|
| > > someone can tell me the difference between image_pattern and
| > > material_map? What can image_pattern do that material_map cannot?
| > > A simple example would be cool :)
| > >
| > > Thanks
| > >
| > > Fabian.
| >
| > That was the very first question asked in this group when it was new.
| > I know because I asked it :)
| >
| >  The answer that Nathan gave me was -
| >
| > This was made for Thomas Baier for use with 3DS to POV conversions.  Let's
| > say you have two textures, and you want to use a black and white image
| > to fade between the two textures.  Now lets say all you have to work with
| > is material_map.  That would be a lot of work.  If you only wanted to use
| > two textures (no fading between), that would be easy, but since material_map
| > uses indices and single textures, fading would be very difficult and you'd
| > have a lot of "average{ texture_map { [0.5 t1] [0.4 t2] }}" statements.
| > You could put it in a while loop, but that would still be a lot of extra
| > work.
| >
| > Now, on the other hand, if you have image_pattern, you can use texture_map
| > instead of material_map, and just use the image as your image_pattern.
| > Simple.  Fast.  Saves memory (no need for 256 textures for those 256
| > shades of grey).
|
| Yes but one can use a gif with only 2 color define in the palette.
| But I feel that I don't understand yet this feature. I certainly need
| an example to see the advantage of this :)
|
| Thanks!
|
| Fabian.

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