In article <slr### [at] fwicom>,
 Ron Parker <ron### [at] povrayorg> wrote:

> Transforming vectors is different from transforming points.  I think the
> transpose of the transformation matrix is involved somehow; I'd have to check
> the code to be sure.

For directions, you transform using the inner 3*3 portion of the matrix 
(basically dropping translation). For normals, you have to transform by 
the transpose of this matrix.

(I recently had to do exactly this, so it is fairly fresh in my mind)

-- 
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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