On Sun, 21 Mar 1999 18:47:47 -0500, david sharp <dsh### [at] interportnet> wrote:
>Now, my question is why does POV-Ray do that? What is wrong with
>one normal pointing 'up' while two point 'down' (or vice versa)?

I guess I should reply to this one, since I submitted the bug 
report that got these classified as degenerate triangles. :)
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.  

If you want to see the original discussion that caused this, 
you'll have to go back a few months on povray.programming.

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