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Hi! I realize this is an old posting from the POV news sever, but you can
go here to see a new technique I created to make waterdroplets do what I
want them to do on a flat, glass surface, and am working on making it happen
on a curved surface. The piece is animated, but here are some screenshots
to look at. All the water droplets on this image are CG created.
http://www.actlab.utexas.edu/~arie/intersection/
Arie Stavchansky
"Per Rutquist" <per### [at] volvo com> wrote in message
news:web.3e43e6949320e9d02ce39a3a0@news.povray.org...
> Water-Glass-Air problem:
>
> I've given this problem a lot of thought while trying to accurately model
a
> glass of Champagne. I've come up with four non-solutions.
>
> Model with air-gap:
> -Doesn't work because it results in total reflection where
> there shouldn't be. (The air gap work the same way as the
> air gaps in optical fiber lines.)
> -Awful render times because of rays bouncing back and forth
> in the gap.
>
> Union with overlap:
> -Not as much total reflection, but still incorrect.
> -Still awful render times, because of the two surfaces.
>
> Merge with overlap:
> -Not really correct since merged objects shouldn't have different
> interiors.
> -The material is determined by the ray's point of entry, and
> doesn't change, because there is no surface at all where there
> were two surfaces before
>
> Union + clipping.
> -Correct number of surfaces (one) between water and glass.
> -Problem when ray reenters air. (It doesn't, because it
> misses the surface where it should leave the water.)
> -Example:
> 1st surface: Enter water (Ray is in water)
> 2nd surface: Enter glass (Ray is in glass in water)
> - Surface to leave water is clipped
> 3rd surface: Leave glass (Ray is in water, when it is actually in
air.)
>
> The only solution that I can think of would be to modify POV-ray itself.
> The feature we need is a half-merge. That is a method which takes the
> union of two objects, and keeps exactly one of the internal surfaces.
>
> /Per
>
>
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