On Wed, 3 Mar 2004 18:50:46 +0100, "Tim Nikias v2.0" <tim.nikias (@)
nolights.de> wrote:

>Perhaps I'll just do some research on raytracing to find out why one would
>need more intersections. Thanks for the tutoring! :-)

IIRC the main need for storing an intersection stack arises from the
way CSG works. Basically to find out the intersection with a CSG
object you need to find the intersections with all its children (and
theirs... recursively). Once you have them, the intersection point of
the CSG objects is the first one among those of its children that is
inside all of them, the one in belongs to is not checked for precision
reasons. The inside test itself is either based on Jordan's theorem
(based on the evenness of the number of intersections from the ray's
origin to the point in question) or is object-specific, whichever is
faster.

Another use is object media. POV needs to know the point(s) of entry
and exit of a media container in order to be able to correctly perform
media sampling in the object's interior.

I hope I'm not talking rubbish, but IIRC at least CSG worker that way
in a raytracer I wrote a few years ago.


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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