"Chris B" <nom### [at] nomailcom> wrote in message 
news:4826bf28$1@news.povray.org...
> ... snip ...
> You can work out the angles, one at a time, by taking the point that you 
> get by projecting point A onto the YZ-plane (project a line through A and 
> through the YZ-plane at right angles). This point will be at <0,A.y,A.z>. 
> You can now use trigonometry to work out the two angles you're interested 
> in, or you can use the VAngleD() function from math.inc (you'll obviously 
> need to take care over angles in the different quadrants).

Sorry. I got this a bit wrong.
To get the 'Y' rotation you need to drop point A down onto the XZ-plane. The 
'Y' rotation is therefore VAngleD(z,<A.x,0,A.z>). To get the 'X' rotation 
you need to rotate point A back onto the YZ-plane so that it lies in +Z. To 
do this, use vrotate() with point A and the negative of the Y-rotation you 
just calculated. This gives you a point B on the YZ-plane that you can use 
with VAngleD(y,B) to retrieve the first rotation angle.

> ... snip ...

Regards,
Chris B.

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