CreeD wrote:
> 
> I guess what I'm looking for is an increase in caustics around the base,
> but without messing up the prism effect too much.

Generally speaking, the higher the IOR of your sphere, the tighter the caustics. 
Dispersion is also effected by this, so you might have to tweak the dispersion
amount as you change the IOR.

> 
> Which do I need to raise the nelems on to eliminate it (I've gone up to 20 so > far)
and how high should it be to look nice at, say, 640x480?

I've gone up to 50. Your mileage may vary.

> 
> Lastly, the ground surface is flat, but I get all sorts of tiny, regular
> streaks in the
> dispersion highlight.

I'm guessing these streaks are just aliasing artifacts of the photon map. You
might try increasing the number of photons or gather radius. But if it doesn't
bother you, let it be.

-- 
Margus Ramst

Personal e-mail: mar### [at] peakeduee
TAG (Team Assistance Group) e-mail: mar### [at] tagpovrayorg

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