Rafal 'Raf256' Maj wrote:

> Micha Riser <mri### [at] gmxnet> wrote in news:3d3ae686@news.povray.org
> 
>> Rafal 'Raf256' Maj wrote:
>> 
>>> Micha Riser <mri### [at] gmxnet> wrote in news:3d3a6e8b@news.povray.org
>>> 
>>>> sphere{<-1,0,0>,2 pigment{rgbt 0.8} finish{ior 1.5}}
>>>> sphere{<1,0,0>,2 pigment{rgbt 0.8} finish{ior 1.2}}
>>>> How does POV-Ray handle this? In the intersection of the spheres
>>>> there are two ior values defined. Which one does POV use?
>>> 
>>> If You have i.e. big box (A) and small (B) placed like :
>>> 
>>> aaaaa
>>> abbba
>>> abbba
>>> abbba
>>> aaaaa
>> 
>> This case is clear as B is compleatly inside A. But what happens if A
>> and B only partly overlap?
> 
> They should not overlap. At least - they can overlap in some not-connected
> points, like sphere { y*0 1 } sphere { y*2 1 }. Point <0,1,0> is inside A
> _OR_ inside B, the result is quite random - it deppends on implementation,
> but if this is 1 separate pint - this artfact probably will not be
> visible.
> 
> If the overlap area is bigger, like
> cone { y*0 1 y*1 1 }
> cone { y*1 1 y*2 1 }
> 
> then area with shape of cone { y*1 1 y*1 1 }will have random artefacts (it
> can be i.e. black pixels)
> 

I think we are talking of different things. With 'overlap' I do not mean 
that big parts of the *surface* overlap. Obviously this has undefined 
result. What happens if the objects have a partly common interior. Maybe 
csg intersection is better to make you clear what I mean:

intersection{
  box{0,5 interior{ior 1.1}}
  box{2,6 interior{ior 1.2}}
}

This results in a box{2,5} but what ior is used?

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