Your diagram is right on.  I had a problem with coincident surfaces
(although I'm at a loss as to how I managed to model a mesh at exactly
y0), so I moved the plane down a little bit.  I'll mess with it some
more to see if I can get rid of it.  

I really like how good this patch came out.  It's not really that slow
considering that half the time is spent rendering reflection and
refraction regardless of the photons.

The only problem I've run into is trying to render caustics from a plane
with a normal on it.  One thing that might be worth adding is a bounding
option to specify an area on infinite objects (or finite objects for
that matter) to shoot photons at.  That way instead of using the
object's bounding box, use one the user specifies.

I noticed that sometimes I would render once and then go to render again
and no photon gathering was done. Then it would only do it again if I
moved a light.  Are you caching the photon maps and reusing them?

-Mike

Nathan Kopp wrote:
> 
> I'm pretty sure I know why it is overly bright, but I'm not sure right now
> exactly how to fix it.  Here's the problem:
> 
>      |______________|    glass
> ------------------------ ground
> 
> If the glass is just above the ground, photons will get deposited on
> both surfaces.  But they are gathered independly from the scene geometry,
> so you end up getting double the photons that you should get.  If you
> set the "ignore_photons" flag in the glass, it shouldn't store photons
> on the glass, so that should work as a workaround for now (speeds the
> render time, too),
> 
> Sorry I didn't include any demo scenes.  Once you get a good shooting
> density & gather density combination, you can usually just reuse that code
> to get started with a new scene.
> 
> One way to get rid of artifacts is to increase the jitter amount.  If
> that doesn't fix it, it probably is because your glass is a mesh.
> 
> Looks great, by the way!
>

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