"Bruno Cabasson" <bru### [at] alcatelaleniaspacefr> wrote:

>
> Try this code. It is some kind of nebula, which is more accurate for comparison
> between renders than simple spheres...
> PS: I just hope that I am not mislead by something so obvious I can't see it!

Sorry I haven't been timely with my comments; I got kind of 'stuck' while
testing out this version of your nebula code--specifically the version with the
light_groups, the example using just the spheres again. I ran across a
light_group problem that I haven't been able to understand or work around.

Given that your light_group code, as-is, has two groups of spheres, each group
in its OWN light_group (and each with its own light): If I comment-out the
light_group container for the UnionSpheres group...while retaining its light..
suddenly *those* spheres appear to be lit by BOTH lights! Yet the
DistinctSpheres group does not (which is correct behavior.) I don't understand
why the light in the DistinctSpheres light_group is now illuminating BOTH
groups of spheres. Aarrgghh, now I'm hoping that *I* am not being mislead by
something obvious!  :-) Looks like some kind of problem with lights_groups...to
add to the scattering media problems!

BTW, I haven't yet said how much I like your nebula(s). Nice work! I've even
learned a few things; thanks!

Ken W.

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