Basic idea is to think of the surfaces of objects as being the ior
calculation point I think might be the way to describe it.  A plane will
refract like a box if you think about it yet not have another side, interior
yes.  Except for certain things like plane, polygon, triangle, bicubic
patch, the entrance and exit of a surface is considered solid up until
meeting another surface of same interior refraction (not other objects, same
object only).  The bicubic mesh from sPatch should be the same when another
part of its surface is met and exited.  Since there are always chances for
bugs with such things I do not know if all meshes work as expected.
I've heard many descriptions of the workings, I'm just not perfectly clear
on it.

--
/* Chimera */

Takuya Arai <tim### [at] stratosnet> wrote in message
news:37e97a7b@news.povray.org...
| In article <37E97191.A83EADD8@pacbell.net>, Ken <tyl### [at] pacbellnet>
wrote:
| > Think of it this way. If you have a standard POV-Ray box primitive and
| >apply an ior value to it Pov will treat it as a solid object. If we take
| >an example of a box created by six individual pieces, each with a known
| >thickness, then apply and ior value to it, Pov will handle the index of
| >refraction of each panel of the box but not the center of it. A good
| >example of this would be a drinking glass. It is a solid material where
| >the outer glass portion is, but the inside is hollow, where the liquid
| >goes. Pov will calculate the ior for the glass but not the hollow space
| >between it's walls.
|
| Hm...now is there a way to create an "inside" in a box made from six
| individual pieces?  I could see something like that if I made a more
complex
| shapes from primitives.
|
| >  In the case of your "sword in a stone" Pov appears to be handling it
| >as one solid object which I presume is what you want. If you
intentionally
| >hollowed out the inside of the stone and gave it's walls a finite
thickness
| >the sword itself would appear differently in different areas of the
stone.
|
| I forgot to meantion that I made the stone in sPatch.  Is it still
treating
| the stone as a solid object?  Since the stone itself is just made up of
unions
| of a buch of bicubic patches....or is the act of using a union make it a
solid
| object without a hollow inside?  Or am I missing the point entirely???
|
| Thanks for the insight though.  It does make sense that POV Ray would
treat a
| primitive as a solid rather than a thin walled hollow object.
|
| Tim

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