I know exactly what you mean now.
It's the different-surface concept, such as the well known water in a glass 
type paradox.
Refraction has been put into the air, simply put, as was said. The sphere then 
is an intersecting surface despite its own composition where no refraction 
exists thus causing the bent rays at that surface. Still plane interior, as it 
were, encompassing the sphere.
Makes perfect sense too. Only wish I had thought of it before myself, but 
maybe others reading here will be enlightened as well.
And damn good thing I didn't send in a genuine bug report to the POV Team!

  :)

Message <36661D7A.C1C15D85@pacbell.net>, Ken  typed...
>
>  Forgetting your thoughts on the hollow key word instead
>lets look at the different objects here and their properties.
>If we took a box, instead of the plane, and assigned it
>a refractive ior value. Inside of this box we place a sphere
>with the value you ascribed of rgbf 1. As you have
>mentioned by itself floating in air the object is technicaly
>invisible. When you place the sphere inside the box on the
>other hand it would be treated as something akin to an air
>pocket inside a glass cube. The rays calculated for the space
>in the cube will be different than those for the rest of the box
>object. While technicaly this is an invalid model but it suffices
>to illustrate the point.
>  The hollow keyword is necessary for pov to understand
>exactly what is inside and what is out. If you wanted to
>place a media inside the box and not the sphere pov gets
>confused as to whose surface normal belongs to who. The
>hollow keyword sets this conditionaly but has no other effect
>on solid objects. In effect the object is really still solid. Only
>the way the objects interior is treated is different when media
>effects are being calculated.
>
>Ken Tyler
>
>=Bob wrote:
>
>> I think I get you.
>> Except for the fact that, what I'm thinking about is, since there is no csg
>> taking place and all the objects are set to hollow (meaning the sphere
>> hollowness should be unchanged regardless) why then isn't it still just a
>> totally invisible object? It ought to be as a container object should be 
for
>> media and not ever become visible when an external object encounters it.
>> I remind you of the fact that *all* objects are set to hollow and inversing
>> any would still make for all hollow (or is this the thing, hollow turns
>> off???). Reason of course being that the outside of any is already hollow
>> anyway, and setting them to hollow is like making the entire scene hollow.
>> Right? or am I still not convincing anyone?
>>
>> Message <36660FC3.9D17DED0@Kopp.com>, Nathan Kopp  typed...
>> >
>> >> // refraction seems to jump into an external object
>> >> // which itself does not have an ior
>> >> // 98.91, bob hughes
>> >>
>> >> // when 1 (inverse used) refraction jumps into sphere, 2 does not
>> >
>> >Actually, this is technically not true.  The sphere DOES have an IOR... it 
is
>> >1.0 by default.  Because this is the same as the air (empty space), when
>> >you don't use inverse, you don't see any effect.  However, when you do
>> >use the inverse, as Ken mentioned, the camera is inside the water plane, 
so
>> >there is a change in IOR values when the light beam passes from the water
>> >(ior 1.23) into the sphere (ior 1.0).  Therefore, POV calculates the
>> >refraction angle properly.
>> >
>> >-Nathan
>>
>> --
>>  omniVERSE: beyond the universe
>>   http://members.aol.com/inversez/POVring.html
>> =Bob
>
>
>

-- 
 omniVERSE: beyond the universe
  http://members.aol.com/inversez/POVring.html
=Bob

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