Re: [help-3dldf] Fwd: Re: button-hole problem

[L. Nobre G.]

> Nobre has
> explained that in FEATPOST, he uses the pyramids whose bases are the polygons
> and whose points are his equivalent of Focus::position for occlusion.  I
> believe the intersections of these polygons can be used to determine which one
> is in front, but I'm still trying to figure this out.

Take, for example, two parallel triangles.

                  A    B
                  /\  /\
                 /  \/  \
                /   /\   \
               /  C/__\___\D
              /________\
             E          F

If AEF is in front of BCD, then

                  A    B
                  /\  /\
                 /  \/g \
                /    \   \
               /      \h__\D
              /________\
             E          F

the plan containing A, F and Focus::position has cut BCD in two parts.
Cgh is occluded and BghD is not.

Greetings

Lu\'{\i}s Nobre Gon\c{c}alves - http://matagalatlante.org