In article <3A61158D.9D409B1B@online.no>, Tor Olav Kristensen 
<tor### [at] onlineno> wrote:

> Hmmm ... Are you sure about this ?

The normal to the -x side of a box is -x. The top of the box is then 
sheared +x so the -x and +x faces are at a 45 degree angle...but points 
still remain in the same xz plane as they were before, the -y and +y 
faces remain perpendicular to the y axis. The normal should be at a 45 
degree angle now, <-sqrt(2)/2, sqrt(2)/2, 0> to be precise, but since 
the two sample points were in the same xz plane, their position relative 
to each other is the same, and the normal is still -x.


> If so, then how would you define a 
> normal of a surface at a given point ?

The vector perpendicular to the surface at that point.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

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