In article <3890BD85.E7A95150@istar.ca>, sde### [at] istarca wrote:

> But a right solution for another problem.
> 
> I was looking at a test tube in my Chem lab yesterday, and noticed the
> ribbons of variable refraction streaming through the liquid.
> 
> It would also be nice to simulate heat lines, and mirages in the desert...

I have often noticed this, and have been wondering how it could be 
done...
Probably the best way would be to follow the ray a short 
distance(specified by a parameter) into the object, sample the ior at 
that point(or actually, the rate and direction it is changing), and 
repeat this process. It would probably be as slow as media, and would 
slow media down(since the path media is sampled over would have to 
change due to the variable ior). It might not be extremely difficult to 
implement, but I don't have the math knowledge to do it.

The syntax would be something like this:
variable_ior {sample_spacing, max_sample_depth, PATTERN}

I also think there should be some kind of float_map_wave waveform 
modifier for patterns(like sine_wave, triangle_wave, etc), it would act 
similar to the slope_map. This would allow a high degree of control over 
the values of a pattern, and would almost be necessary for this 
variable_ior thing to be useable. This is one I might be able to 
handle...

-- 
Chris Huff
e-mail: chr### [at] yahoocom
Web page: http://chrishuff.dhs.org/

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