"Kenneth" <kdw### [at] earthlinknet> wrote in message 
news:web.4a1503ebc981982af50167bc0@news.povray.org...
> "Chris B" <nom### [at] nomailcom> wrote:
>> If you add a real
>> spark plug into a cylinder block you'd normally have to cut a hole in the
>> cylinder block first.
>
> It seems to me that a
> way around this limitation would be: whatever individual object 'volume' 
> the
> camera ray hits at the cutaway surface, that's the color that should be
> returned. The color of the 'innermost' of any nested objects there, if 
> that
> makes any sense. (And I may not be thinking *this* idea through to its 
> logical
> core.)

In my example I showed the union of a cube and sphere. The middle of that is 

stick out at different places (they take it in turns to be the outermost 
object), so you could say that the ray really hits both object 'volumes' at 
once.  There are parallels in the real world, particularly with liquids, or 
solids that have solidified from overlapping liquids at which point you get 
a sort of average of the two colors. So a tub of striped ice cream where 
part of the junction between two colors has melted and refrozen gives you 



> But apparently, POV's ray-tracing process currently doesn't work on
> 'mathematically-created' objects this way (like a box or cylinder, etc.) 
> I.e.,
> there's no real internal 'structure' to such objects that a ray can look 
> at at
> a particular point in space.

Some of the POV-Ray media functions can provide certain forms of internal 
'structure' with the consequent processing overhead. The less processor 
intensive options mostly handle the surfaces of the objects.

Regards,
Chris B.

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