Ken wrote:
> 
> If I have an object constructed using a CSG operation I get
> two different results in the rendered object if I apply the
> pigment and interior properties to the different pieces
> versus the CSG as a single object ( see example ).
> The difference is quite visible.
> 
> Why ?
> 
>  intersection{
>    cylinder{x*-3,x*3,1
>     pigment{rgbf<1,.7,.7,1>}
>      interior{ior 1.95}
>   }
> 
>   plane{-z,-0
>    pigment{rgbf<1,.7,.7,1>}
>     interior{ior 1.95}
>   }
>  }
> 
> vs.
> 
>  intersection{
> 
>  cylinder{x*-3,x*3,1}
> 
>  plane{-z,-0}
> 
>   pigment{rgbf<1,.7,.7,1>}
>    interior{ior 1.95}
>  }
> 
> --
> Ken Tyler
> 
> tyl### [at] pacbellnet

I'll take a wild guess.

Perhaps in the first case when a ray hits the plane within the cylinder,
it is considered to be entering the plane with ior 1.95 and also
entering the cylinder with ior 1.95, so POV does something like multiply
the
iors.

In the second case, which is done 'correctly', the ray enters a single
CSG object with one ior and so POV
knows how to deal with it.

I say that the second example is correct because if the iors were
different the result would not represent
any real world situation.  The ior would be different depending upon
which face of the object a ray entered.

Cheers, PoD.

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