I've been rendering quite a few illustrations for

http://news.povray.org/povray.off-topic/message/%3Cweb.5f3045d617b7b05f1f9dae300%40news.povray.org%3E/#%3Cweb.5f3045d61
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and have been mixing the very broad strokes with digging into the very detailed
bits.

At the moment, having some issues with smooth_triangles and want to verify a few
things, so I want to make sure everything is absolutely correct. Assume I'm
laying out a grid of squares made up of 2 triangles each.

All my flat triangles are fine, and I can see all of the individual triangles,
since all of the face normals are sufficiently different.

With smooth_triangles, even though the vertex coordinates are the same,
sometimes I get the degenerate triangle warning when working out the vertex
normal vectors.

When I use the corners of the square to calculate the normals, the edge between
the two triangles of the square softens/goes away, but the edges between all of
the squares are still pretty abrupt.
When I try to use a small dy or dx offset to calculate the normals, I get a lot
of the degenerate triangle warnings and few if any visible triangles.  Not sure
why.

So:

When calculating the normals, do I use the remaining two triangle vertices, or
the orthogonal edge vectors of the square?
Do I normalize the vectors before using vcross()?
Do I normalize the resulting vertex normal vectors?


Thanks

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