Takuya Arai <tim### [at] stratosnet> wrote:
: 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.

  Povray only handles (mathematical) surfaces, not solid 3D objects.
  The algorithm for refraction is pretty simple: First the ray is "outside".
When the ray hits the surface, another ray is shot from there (varying its
direction depending on the ior) and this ray will be "inside". When the
ray hits the surface of the same object again, the new ray will be again
"outside".

  New users often don't realize that objects are only surfaces and nothing
more.

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

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