[Radiance-general] splitting a render by light sources - rtcontrib

[Gregory J. Ward]

Hi Will,

The spotlight type is designed to make the calculation more efficient  
by avoiding testing for light sources that don't stand to make a  
contribution.  If you used the regular "light" type with a narrow  
spot fixture, it would check for source visibility at all angles,  
only finding out the contribution was zero afterwards.  Using the  
spotlight source, you can preempt this test for angles past the  
normal cut-off of the fixture.

This is less important since the introduction of adaptive shadow ray  
testing way back in 1991, but it was left in there for legacy reasons  
and because the code is handy for the virtual light source handling,  
anyway.  (Long story.)

-Greg

> From: william reynolds <william.reynolds at oriel.ox.ac.uk>
> Date: January 29, 2006 11:11:38 AM PST
>
> Greg
> Thanks for your help. I will play with the -dj settings to get a  
> better picture.
>
> as for the spotlight type light, i am still at the "pretty basic"  
> stage with my model - i will hopefully use real lighting fixture  
> specs to model real instruments in the not too distant future!  
> having said that, i dont really follow waht you mean by "set the  
> cut-off past the natural cut- off of the fixture". could you  
> explain a bit more please.
>
> thanks once again
> will