Thomas de Groot <tho### [at] degrootorg> wrote:
> Op 09/11/2021 om 20:02 schreef Kenneth:
> >
> > BTW, I did not realize that an object with ior could have inclusions (other
> > objects) with *different* ior's-- I thought such constructs would be an example
> > of 'variable' ior within an object, which cannot be accomplished in POV-ray,
> > AFAIU. I had a mistaken notion that the camera ray would 'see' the outer object
> > surface first, (...)
> >
> To tell the truth, I really do not know /how/ the different ior's are
> treated together. Afaik, this is not explained in the wiki pages. To
> keep on the safe side, I kept the inclusion's ior at 1.0 which is
> cheating of course, but at least I was not confronted to strange
> effects.

If I'm not mistaken, a ray evaluates all objects and their iors along its path
and changes its trajectory accordingly. So in a union, it is not really
'cheating' to have objects with an ior of 1 inside. They are treated as air
until the ray moves on. It's a reasonable alternative to using a difference
which - while not requiring objects with different iors - is very slow to trace.

Oh, and a while back, I found out that if you want to pretend that the camera is
inside some volume, say water, and you want to see air bubbles in that volume,
then for the air bubbles you would use the reciprocal of water's ior. So, the
bubbles would have an ior of 1/1.325, iinm.

Sam

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