I posted this to comp.graphics.rendering.raytracing but I thought I'd post 
this here too.

I have a really basic question of how POVRay handles light going through a
transparent object.  For example, say I made a chunk of rock with some edges 
so it has a vaguely crystal look and made it into a reddish ruby color and 
transparent (or translucent...can't remember the proper term).
                     
Obviously POVRay will calculate the index of refraction of the light going in. 
I think you can change that too.  However, my question is, how does POVRay 
calculate the thickness?  If the rock is hollow in the middle then the light 
wouldn't bend as much when it shines through as it would if it was solid.  
Does POVRay assume it's a solid?  Is it dependent on something?  It's really 
not that big of a deal but I'd like to know more for the academic standpoint 
for now.
                     
I made a quick and dirty render.  Essentially a sword in a stone type thing 
and made the stone that ruby chunk so I can see the tip of the sword inside 
the rock.  Obvioulsy there's distortion because of the ridges on the outside 
of the ruby but I'm wondering just how accurate the bending of the blade is.  
If you want, it's at:
                     
http://members.stratos.net/tima/images
                     
and it's the file swordinstone.jpg
                     
Anyway, if any of you can shed some light on this subject, I'd really 
appreciate it.  If you reply to this, please also send me a copy via e- mail 
since I dont' read this group too often.
                     
Thank you in advance for any help.
                     
Tim

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