[Radiance-general] Re: Ambient mess

[Greg Ward]

Hi Bruce,

Interesting problem.  I presume that you don't see this unless you run 
the image through pcond, which makes the darker areas visible.  Did you 
try applying the -h option of pcond?  This might reduce the appearance 
of these splotches considerably.

Getting at the heart of your errors, they are really due to the 
low-angle light coming in from the horizon on the outer perimiter of 
your model.  Your idea of placing a "mkillum fence" around the 
perimiter is a good one, and might well eliminate these splotches.  
Make your polygons out of "void" and completely surround your building 
with a fence as high as the top of the roof.  You might get another 
artifact from this, though, which will be the unexpected appearance of 
a bright line right near the mkillum fence, even though the fence 
itself will be otherwise invisible.  I'm not sure how to avoid this.

Do you really want to see the spill light on the surroundings?  
Typically, moonlight would drown this out.  If you added a moon, you 
might not even notice your splotches anymore.  You could also exclude 
the surrounding material using the -ae option.  You won't get the spill 
light anymore, but the splotches would be gone with it.

-Greg