In article <3a0f9ac9@news.povray.org>, "Mark Wagner" 
<mar### [at] gtenet> wrote:

> Wrong.  IOR is defined as the *ratio* of the speed of light in a 
> given material to a reference material (usually, the reference 
> material is a hard vacuum).

Ok, thanks for the info...I wasn't certain about there being a lower 
limit to ior. I dimly remember reading about the exact meaning of ior, 
but not reliably enough to claim only positive values are allowed.


> If an object has a negative IOR, it implies that light entering the 
> object will have a negative velocity -- it will enter the object, 
> stop, turn around, and head back the other direction!

Which would probably look like a reflection in most cases...possibly a 
useful effect.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

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