On Sat, 11 Dec 1999 23:17:40 -0500, Michael Paul wrote:
>"Jon S. Berndt" wrote:
>
>> I've been thinking about this one, too (non-linear transformations).
>> It's a difficult problem. It would be easy (relatively) to take a shape
>> and skew it based on some function. However, I think there would be a
>> lot of work to also take into account surface normal, textures and
>> everything else which dictates what an object would look like at a
>> skewed point. I don't think it is impossible at all, just a very tricky
>> and uncomfortable problem. I sure ain't the guy to take on that one!
>
>Transforming normals isn't too hard.  I don't remember the formula
>offhand for deriving the normal-transformation matrix from the
>point-transformation matrix, but it's in Andrew Glassner's "Graphics
>Gems".

There's a function (or perhaps a macro) for this in POV, too, but it assumes
that your transformation is a matrix, which a nonlinear transformatio isn't,
by definition.

-- 
These are my opinions.  I do NOT speak for the POV-Team.
The superpatch: http://www2.fwi.com/~parkerr/superpatch/
My other stuff: http://www2.fwi.com/~parkerr/traces.html

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