In article <MPG.16c13f9478298a549896d4@news.povray.org> , Lutz-Peter Hooge
<lpv### [at] gmxde>  wrote:

> When a ray first enters an object of, say ior 1.5, and then one with ior
> 1.3 (without leaving the first object), is that IOR than regarded
> relative to the containing object, or absolute?
> And, when the ray than leaves the second object, does it "remember" that
> the outside has ior 1.5?
>
> The reason I ask is, I made a glass with a liqid inside.
> The common way to do this, is to scale the "liquid" by, .999.
> But this causes the render to become very slow, because of reflections
> between the liqid and the glass, because there are now two surfaces where
> in reality there should be only one. So I had the idea to clip the glass
> by a slightly bigger inverted copy of the liqid.
>
> This is much faster, but I'm not sure if it gives correct results?

Not sure if it is anywhere else, but the 4th paragraph of
<http://www.povray.org/working-docs/id000174.html#6_6_1>
explains how and where the ior is used.

    Thorsten

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

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