"Chris B" <c_b### [at] btconnectcomnospam> wrote in message 
news:447373ce$1@news.povray.org...
> Hi Sean,
>
> Technically, yes it is possible, though I'm not sure I'd cite it as a 
> particularly 'newuser' thing to do.
>

Here's a short example, but be warned it uses some fairly complex notions so 
it might be very difficult to follow.
I've tried to use some fairly explicit names, but if you don't understand 
something, just ask and I'm sure someone will be happy to explain.


light_source { <0, 50, -50> color 1}
light_source { <20, 40, -10> color 1}

#declare InternalObject = cylinder {0,1,0.2}
#declare InternalObjectCentre = (min_extent(InternalObject) + 
max_extent(InternalObject))/2;

#declare CameraLocation = <2,2,-4>;
camera {location CameraLocation look_at InternalObjectCentre}

// Build an object for the object pattern
#declare DistanceFromObjectToCamera = 
vlength(InternalObjectCentre-CameraLocation);
#declare I = 0;
#declare Slices = 400;
#declare ShadowObject = merge {
  #while (I<Slices)
    #declare DistanceFromObject = DistanceFromObjectToCamera*I/Slices;
    object {InternalObject
      translate -InternalObjectCentre  // Move to origin
      scale 1.04*(Slices-I)/Slices          // Scale
      translate  InternalObjectCentre  // Move back
      translate 
DistanceFromObject*vnormalize(CameraLocation-InternalObjectCentre)
    }
    #declare I = I + 1;
  #end
}

// The inner object
object {InternalObject pigment {color rgb <1,1,0>}}

// The outer object
object {box
  {-1,2
    pigment {
      object {
        ShadowObject
        color rgbt <0,1,1,0.5>
        color rgbt 1
      }
    }
  }
}

Higher values for 'Slices' will give a smoother 'hole'.
The scale factor (1.04) gives a hole slightly bigger than the object. Use a 
scale factor of 1 to get a snuggly fitting hole.


Regards,
Chris B.

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