Hi Paul,
Just an addition to the above. This works as long as the transparent
object consists of a fully closed shape (which is the case here). If it
weren't you'd introduce new artifacts by culling transparent faces that
should be visible.
As an addition to the above, even with a manifold object, culling back
faces is not correct because the back faces should be visible through
the front faces, and should also affect objects behind the transparent
object. Imagine a glass jar where the part facing you is transparent
(untinted, say (1,1,1,0.2) ) and the part facing away is tinted red (say
(1,0,0,0.2) ), then objects behind the jar should be tinted red because
you're seeing them through the red-tinted glass, but if you cull away
the back faces they will not be.
A more correct solution is to render the object twice, once with front
faces culled, then with back faces culled. But in general, the only
fool-proof solution is to sort faces back to front, which is not
generally feasible in a realtime application given the tradeoffs it
involves (see Real-Time Rendering 2nd ed. by Akenine-Möller and Haines,
pages 101-106).
Real-time graphics is often based on approximation, so you must decide
which approximation is acceptable for your application. It could be that
culling the back faces is good enough.
Hope this helps,
J-S
--
______________________________________________________
Jean-Sebastien Guay [EMAIL PROTECTED]
http://www.cm-labs.com/
http://whitestar02.webhop.org/
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