[Radiance-general] Math Help Needed

[Mark de la Fuente]

Hi group,
 
I'm trying to write a tool for calculating the rotation angles necessary to aim a light fixture.  The tool will basically export a text file from AutoCAD containing xform rotation and transformation commands.
 
So far I've been approaching this problem using vectors (one at the fixture origin oriented down and one for the aiming direction based on the coordinate points of the source and target) and using the dot product to find the angles between the vectors. Unfortunately so far this only works for some cases.
 
Is there a better way to approach this?
 
Thanks for any input.
 
Mark

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