FelixKlein nous apporta ses lumieres en ce 2005-06-09 14:38:
> I have observed a curious difference in performance when rendering a scene
> after just changing the lights.  It's quite drastic:
> 
> Single point light at <0,0,8>:  320x240 renders full scene in 40 seconds
> Single point light at <1000,2000,10000>: 320x240 renders 3 rows in 11 hours
> 
> The scene contains one plane (the "ground") and a union of a little over 6
> million spheres with a "Polished_Chrome" texture.  The spheres are mostly
> very small... for example, there are about 50 of radius greater than 0.1.
> All are centered on the "ground plane".
> 
> Can anyone explain this drastic change in render time?  Better yet, can you
> suggest a way to simulate a distant point light without increasing the
> render time significantly?
> 
> Thanks!
> 
> 
A way to simulate a *very* distant light is to make it a parallel one. If using such a
light, you 
need to specify a point_at coordinate just like with a spot_light. Don't place it to
close if you 
want shadows, as anything behind it's plane will get light, but won't cast nor receive
any shadow.

Alain

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