[Radiance-dev] Errors in ambient calculation in 3R7P1?

[Mark Stock]

I am testing a new benchmark scene to replace the old "mirror 
pyramid" scene, and I came across some strange behavior in the 
3R7P1 release.

The benchmark scene and spase table is at:
http://mark.technolope.org/pages/rad_bench.html

The 3R7P1 image in question is:
http://mark.technolope.org/radmisc/bench4_02.png

The same commands, under 3R6P1, created this:
http://mark.technolope.org/radmisc/bench4_01.png

So, neither of the images are perfect, but the large black areas 
in the 3R7P1 image worry me. I have tried very similar scenes 
with nearly similar parameters, and every other time I run it, 
those dark spots appear on the fractal object in the middle. I am 
still running more tests on every Radiance install that I can 
find.

Some notes about the benchmark scene: I tried to include a 
greater variety of commonly-used Radiance objects and modifiers. 
The majority of the time spent, though, is still in the ambient 
calculation---the forte of our favorite software. But I included 
a large colorpict/mixpict, an obj2mesh object (with normals), 
plastic, interface, glass and metal, daylight and electric light, 
and large and small features. The render takes long enough that 
parallel machines of 2010 still won't be able to finish it in 
less than a minute. The bench2 scene saw speed improvements of 
nearly 100-fold over it's 5-year history. Any comments about the 
benchmark scene are also welcome.

Thanks!

Mark