Ron Parker wrote:
[ ... ]
> The problem is, those triangles cause division by zero errors
> on Alpha processors.  There is no way to have the normal go
> from "positive" to "negative" without going through zero, so
> there is always a curve on such a triangle where the normal
> is undefined.  Since POV always needs a valid normal to compute
> shading, that's a bad thing.


Hmmmm, I just assumed that POV was rotating the normals from one 
triangle corner to the next, in which case I don't see any 'zero' 
normal. 
Your comment makes me believe that what POV does is interpolate the 
vector coefficients independently.
(ie, n1.x -> n2.x, n1.y -> n2.y, n1.z -> n2.z linearly, not rotating
the normal).
(or does this question just demonstrate my complete misunderstanding)

Post a reply to this message