> Alain wrote:
>> May be worth looking at your media. Do you have intervals set to
>> anything larger than 1? Bring back to 1 and adjust samples as needed.
>> intervals 10 samples 5 is much slower than samples 100 intervals 1.
>>
>> How many dispersion_samples?
>>
>> It don't looks like a memory isue, unless you have a ridiculously low
>> amount in your computer, as you use less than 500 Mb.
>
> Yeah the media's one thing I need to fix and save back to the library...
>
> Really, the thing that's making it slow is the refractive objects. I
> could slap no_image on them and get the nice media/photon effects in a
> few minutes. Turn off the media and photons and have the tetrahedra on
> and it takes a few days.
>
> Is there any way to speed that up? How do commercial renderers compare
> speedwise for refractives? What do they do differently?
>
> --
> Tim Cook
> http://empyrean.freesitespace.net

Then, what is your max_trace_level and adc_bailout?

Often, adc_bailout 0.01 is good enough.
Your main problem looks to be many total internal reflections. With 
dispersion, you can get total internal reflection for blue, but not for 
red. This leads to partial doubling of the rays, blue is reflected but 
cyan to red goes through with some added reflection, and the spawning of 
still more dispersion rays.

What's the value for dispersion_sample? A somewhat smaller value could 
be enough.

One other thing that you can try, rotate the tetrahedra a small bit. It 
could be all that's needed to prevent extremely long internal paths.

Some comercials products seems to have quicker bailouts. Other may skip 
on the dispersion, or fake it even more than POV-Ray does, or only apply 
it for the first or last refractive surface encountered before hiting an 
opaque surface. Some don't even support dispersion.


Alain

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