"Bald Eagle" <cre### [at] netscapenet> wrote:

>
> But the information that I need to do that is:
> POV-ray shoots a ray in the direction specified by `inside_vector` _FROM_ ---
> where?

That's something I've wondered about as well.

From newsgroup comments years ago, my own understanding about inside_vector is
currently this (and I could be wrong):

1) it isn't used until the mesh is CSG'd with some other object.

2) Perhaps the 'shoot-from point' (or from *multiple* points) is actually the
surface of the other intersecting object. That would *seem* to make sense--
because a successful vector direction should naturally point toward the inside
of the now-partial 'hull' (of the mesh object), *as seen from* the other
object's surface.  And if the mesh isn't a completely CLOSED one-- if there's a
'hole' in the mesh somewhere-- then the chosen inside_vector direction (if not a
'good' one) could conceivably point at that hole, with NO surface triangle being
detected there... resulting in that particular part of the CSG construct not
being rendered at all. (Possibly an example of the 'odd/even' rule that Clipka
mentioned?-- a hole returning 'ZERO intersections', which is 'even'.)

It's also my understanding that each and every triangle of the 'partial CSG'd
hull' is tested with the inside_vector. In other words, it isn't just a one-time
affair.

That's about as far as I've gotten ;-)

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