On Tue, 12 Mar 2002 13:33:35 +0100, chaps wrote:
> Hi Bob,
> 
> Do you know the value of tangent before all rotation?
> 
> If yes, you only need the same transform to this tangent and you get the new
> value. (I'm not sure that it is true if scaling with non isotropic value,
> for example <1,2,1>. What doe's news group think about this.).

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.

-- 
#local R=rgb 99;#local P=R-R;#local F=pigment{gradient x}box{0,1pigment{gradient
y pigment_map{[.5F pigment_map{[.3R][.3F color_map{[.15red 99][.15P]}rotate z*45
translate x]}]#local H=pigment{gradient y color_map{[.5P][.5R]}scale 1/3}[.5F
pigment_map{[.3R][.3H][.7H][.7R]}]}}}camera{location.5-3*z}//only my opinions

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