Hello.  Long time lurker, saw some of the same issues I have had to deal
with in the past:

"Anthony D. Baye" <ant### [at] sdsmtedu> wrote in message
news:40E99166.75AEBA73@sdsmt.edu...
>     I fixed the spray problem.  I had the particle distribution set way
> too high, so all I was getting was a fine mist.
> the Isonsurfaces, it turns out, aren't the culprits.  Most of the 36 hr
> render time was taken up by the water texture and the glass.

Unfortunately I missed what hardware you were using, even so that seems like
a long time for this scene.  What is the render time without photons?  Have
you tuned the scene for speed (ie added collect off as needed)?

>     The water is a difference (I cut out the shapes of sumberged objects
> to prevent co-incident surfaces and to keep the water out of places it
> wasn't supposed to be.

I am not sure that is required.  Co-incident surfaces are not an issue if
one object is completely within another.  Artifacts only appear where 2
surfaces are occupying the same space.  Intersections between objects and
objects inside of objects do not cause artifacts.

>     Additionally, I use an interior:
>
> interior {
>     fade_power 1001
>     fade_distance 17.5*ft // ft = 12
>     caustics 0.625
>     }

If you are using photons correctly, you should not use caustics.  Caustics
only simulates the same effect photons produce.  I highly reccomend adding
an ior of 1.33 for your water object.  The values for fade_distance and
fade_power are a little unusual, I prefer to use an absorption media to
simulate light attenuation in water, but what ever works.

>
>     Not surprisingly, the Spray is what takes the largest ammount of
> time to render. This may have something to do with the somewhat high
> max_trace_level I specified to avoid black spots (max_trace_level 10, I
> couldn't figure out what the default is.)

If the texture for the spray is partially transparent, it will take the
scene a lot longer.  I think the default max_trace_level is 5 or so.

> I get odd results when rendering with photons, though.  It seems to
> treat the transparent surfaces as though they were opaque (that is, the
> surfaces are still transparent, but the light doesn't seem to get
> through.  I get a solid shadow on the ground to the left instead of
> having a lighter area for the dome, and a colored shadow for the
> crystal.), and nothing I do fixes the problem.  If anyone has an Idea
> about what I can do to fix this, I'd appreciate suggestions.

Inside of transparent or reflective objects, you need to set the object
photon block, something like:
object{
    myobject
photons{
    target 1.0
    reflection on
    refraction on
    collect off // prevents caustics from being calculated onto the surface
of the glass
        }
}

This causes povray to calculate the photons for that object.  By default,
all objects in a given scene behave as though they will be lit by photons.
You can significantly speed rendering by putting collect off in objects that
will not be struck by photons.

// doesn't get hit by photons, speeds rendering by not calculating photons
for this object
object{
    myobject
photons{ collect off }
}



HTH,
Reactor

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