Jim Charter <jrc### [at] msncom> wrote:
> I think you have the correct concept that the image_map texture is
> indeed "extruded" along the z axis.
> However to POV the box is just six defined surfaces, so it only
> evaluates the texture where it intersects with any of those six surfaces.

I would add that textures, by definition, are only "surface" things.  What
you were expecting would be considered the "interior" of the object...the
extrusion *through* the box. Normally, when you carve away an object,
you still see the texture on the new surface. But here, the alpha-channel
transparency is, I believe, "altering" or overriding that (though that
may not be a proper explanation for what's happening.)

Awhile back, I posted an experiment using MEDIA to get what looks like a
solid extrusion from an alpha-channel image_map, same as your idea.
It would do what you're looking for, I believe. Coding it is a bit
complex, though.  Here's the link...

 http://news.povray.org/povray.binaries.images/thread/%3Cweb.4436e54a72fe66658ad7a9060%40news.povray.org%3E/

It appears that my test image is no longer showing there as a thumbnail, but
you can still download it.

An alternate idea would be to make a height_field from your image (though it
would have an open "back," since a heightfield is just a surface or shell.)

Ken W.

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