When using uv-mapping is it possible to specify different uv-coordinates for
different textures on the same mesh, other than matrix transforms?

What I want is something like what OpenGL does where you can specify for one
vertex different texture coordinates for each texture unit.

Imagine an airplane. One would use one texture for the overall paint scheme
and use another higher resolution texture only for those areas that carry
markings, etc. By restricting the second texture to certain areas of the
mesh it could be high resolution an still small in overall size.

Hence, one would require two different sets of texture coordinates at each
vertex.

Is such an approach feasable with POV-Ray?

Regards,
Uwe

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I know the OpenGL technique you're talking about. It's very useful in the 
limited memory, pixel based texturing world of realtime graphics, but in POV 
there's not much need to have low res textures, and you can have infinite 
res if you use pov's internal patterns.

Anyway, as far as I know you can only have 1 set of uv coords on a mesh, so 
your only option is to make layered textures and use transforms to place the 
higher res textures where you want.

It wouldn't be too hard for pov's syntax to support it, so each set of 
uv_coords could specify a number, and then you could do layered textures 
specifying which set of uv's you're using (if any) on each layer, maybe one 
of the unofficial pov versions supports it?

In fact if you're feeling adventurous you could do it with #macros: write a 
macro to independently matrix transform each texture layer for each polygon, 
based on a set of input vertex uvs... but that would possibly be slow and 
certainly be a bit OTT.
-- 
Tek

"uwe" <nomail@nomail> wrote in message 
news:web.454908cf8aed7920a6d1183e0@news.povray.org...
> When using uv-mapping is it possible to specify different uv-coordinates 
> for
> different textures on the same mesh, other than matrix transforms?
>
> What I want is something like what OpenGL does where you can specify for 
> one
> vertex different texture coordinates for each texture unit.
>
> Imagine an airplane. One would use one texture for the overall paint 
> scheme
> and use another higher resolution texture only for those areas that carry
> markings, etc. By restricting the second texture to certain areas of the
> mesh it could be high resolution an still small in overall size.
>
> Hence, one would require two different sets of texture coordinates at each
> vertex.
>
> Is such an approach feasable with POV-Ray?
>
> Regards,
> Uwe
>
>

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