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Does PovRay support shader?
Why not?
Difficult?
or Unnessecary?
Thank you.
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> Does PovRay support shader?
A mutant of Povray called Povman, does. It's not yet an official part of
Pov.
> Why not?
I suppose the code is not good enough yet.
> Difficult?
> or Unnessecary?
Don't know.
Regards,
Hugo
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Difkvol hadani wrote:
> Does PovRay support shader?
If you mean shaders as in RenderMan, then answer is no. But unofficial
verion (POVMan) does it in limited way. It can be found there:
http://tofbouf.free.fr/clothray/download_en.html
> Why not?
>
Ask POVTeam. My speculations:
nobody really-really wanted it
nobody has time/knowledge/wish to implement it
legal problems with Pixar
portability considerations
shader paradigm does not fit into POV-Ray paradigm
> Difficult?
Depends. Implementing all the stuff from RenderMan shaders spex means
implementation of half of ray-tracer...
> or Unnessecary?
Probably. POV-Ray itself it quite powerful and in some cases same
outcome could be achieved with POV-Ray textures/pigments/functions.
One problem is different conepts: in RenderMan (all) surfaces
are parametric and have uv parameters and surface derivatives could
be calculated, this makes shaders really powerful. POV-Ray does not
have support for uv-surfaces
(MegaPOV and 3.5 beta have for some primitives) and using uv and their
derivatives can be done in very limited way. Thats why derivative support
is not yet implemented in POVMan (additionally I'm lazy and don't have
as much free time as I'd like to have.) For antialiasing in shader code
ray differentials could be used, but this probably means, that RenderMan
shaders could not be used without modifications.
Shaders are usually slower than 'native' textures/pigments, this is one
limiting factor. Additionally handling separate files and performing
separate compiling of shaders (as it is now in POVMan) seems to be too
much for some POV-Ray users.
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On Mon, 18 Mar 2002 19:36:39 +0200, Vahur Krouverk <vkr### [at] comtrade ee>
wrote:
> POV-Ray does not have support for uv-surfaces
> (MegaPOV and 3.5 beta have for some primitives)
With some workarounds all objects in 3.5 can be uv-mapped.
For sample of uv-mapped isosurface check:
http://news.povray.org/povray.binaries.images/19777/
ABX
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> With some workarounds all objects in 3.5 can be uv-mapped.
It's quite difficult to define uv-coordinates for some objects. For
triangles it's extremely trivial (and useful): Each vertex has its own
uv-coordinate. However, for some mathematical surfaces it can be quite
difficult to just decide where to put the uv-coordinates.
--
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -
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