[Radiance-general] Affine Transformations in Rcalc?

[Greg Ward]

You can use an appropriate rotation matrix a la:

	http://en.wikipedia.org/wiki/Rotation_matrix

Once you figure out the coefficients, you can apply them in dot products to your origins in rcalc.  For example, rotating about the Y-axis by 41.7 degrees:

	rcalc -e '$3=$3;$4=$4;$5=$5' \
		-e 'th:41.7*PI/180' \
		-e 'c11:cos(th);c12:0;c13:sin(th)' \
		-e 'c21:0;c22:1;c23:0' \
		-e 'c31:-sin(th);c32:0;c33:cos(th)' \
		-e '$1=c11*$1+c12*$2+c13*$3' \
		-e '$2=c21*$1+c22*$2+c23*$3' \
		-e '$3=c31*$1+c32*$2+c33*$3' input.ray | rtrace ...

Hope this helps.
-Greg

> From: "Randolph M. Fritz" <RFritz at lbl.gov>
> Date: August 15, 2011 2:44:25 PM PDT
> 
> I have a series of rays intended for input to rtrace.  I would like to be able to rotate the starting point and direction of these around the origin.  Is there any simple way to do this with rcalc ro some other Radiance tool, or do I have to find another way?
> 
> -- 
> Randolph