In article <glb09ucfqm2gani7cmill9q035608e2rtg@4ax.com>,
 Peter Popov <pet### [at] vipbg> wrote:

> You know, I've never done it that way. Doesn't make much sense unless
> some tangents are involved. A normal is, after all, a vector. The only
> thing you might want to do is to normalize the result if you need a
> unit-length normal. So I don't get the transpose idea.

Try unevenly scaling a sphere. A vector from the center to a point on 
the surface (the normal of an unscaled sphere) goes one way, but the 
normal goes the opposite direction. And how about shearing a box? You 
will end up slanting the normal of the sides which don't change 
orientation.
I don't really understand the reason the transpose does what it does, 
but it is needed. This was discussed in some of the old Ray Tracing News 
articles.

-- 
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/

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