Bryan Valencia <no### [at] waycom> wrote:
> Shaders are widely used in game engines.

  They are used in all kinds of renderers. 3D hardware just happens to
have their own standardized (but somewhat limited) shader languages.

>  They quicken the process of 
> shading without the accuracy of actual raytracing.

  That's not actually the purpose of shaders. The purpose of shaders is
to offer a more flexible and powerful way of creating surface texturing.
In other words, instead of having a fixed set of hard-coded texturing
algorithms, a more flexible shader language is offered for creating new
types of texturing.

  As I said, shaders are not used exclusively in 3D hardware. They have
been used for quite a long time in many rendering software.

> it's a major component in the ability to render 60fps instead of 1fpd.

  Not really. It's just a major component in getting nice texturing
effects. 3D hardware just happens to support a (somewhat limited) shader
language which you can use to create some nice texturing effects, and
naturally they render it quite fast.

  However, the images do not render fast *because* of shaders (as you seem
to imply). They render fast *regardless* of shaders. The shaders simply
provide nice texturing effects.

> It's completely out-of place in POV-Ray because:
> 1. The math is very mesh-centric

  Incorrect. Shaders are not necessarily at all related to triangle meshes.
I fact, AFAIK, for example renderman shaders are quite independent of the
rendering model used.

  Intersection points, normal vectors, texture colors, etc. are not
dependent on the object type used.

> 2. There are more photorealistic ways to accomplish the same thing using 
> radiosity, ambient, and local lighting.

  You can't achieve everything with those, which you can achieve with
shaders. Besides, shaders can sometimes "fake" things so that they look
convincing but with the advantage of rendering much faster.

> I may be wrong, but how would you mathematically apply a shader to the 
> surface of say a blob, or an isosurface?

  Easily. Everything a shader needs is information about the intersection
point, normal vector, texture, etc. Nothing of this is dependent on the
type of object used.

-- 
                                                          - Warp

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