On Sun, 05 Dec 1999 14:05:34 -0800, Ken wrote:
>
>
>Margus Ramst wrote:
>
>> 
>> Glad to hear you solved the problem. But I'm not sure I understand. You have two
>> light sources, in line with the camera, and the spot light in the background was
>> causing the media to display as white spots, right?
>> But why is it 'a silly mistake' to expect this spot light to work correctly with
>> scattering media? Why should the media display as white spots?
>> 
>> Margus
>
>  Your guess is as good as mine. Media is a tricky beast and I will be the
>first to admit that I am not a master with it.
>
>  This should be enough for you to recreate it for yourself. For the two
>point light sources turn media interation = on and you should see the
>problem immediately.

The spotlight isn't necessary to get this effect.  The problem, as I had 
suspected, is that the sampling interval for the point lights is essentially
infinite, so the chance of getting a sample that scatters the light from the
point sources is vanishingly small.  If you add a backstop like

 plane {-z,-500 pigment {rgbt 1}}                     

to the scene, it renders as expected (though it's all white.)  Notice the 
lack of the hollow keyword.  Since I didn't expect significant contributions
from the media beyond 500 units, I elected to remove it from consideration and
speed up the render a tad.  (indeed, if you add hollow it's still all white,
as expected.)

-- 
These are my opinions.  I do NOT speak for the POV-Team.
The superpatch: http://www2.fwi.com/~parkerr/superpatch/
My other stuff: http://www2.fwi.com/~parkerr/traces.html

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