🚀 go-pugleaf

In article <1991Apr8.181450.15309@cs.cornell.edu>, ressler@CS.Cornell.EDU (Gene Ressler) writes:
> In article <41021@cup.portal.com> Bobster@cup.portal.com (Robert Jules Shaughnessy) writes:
> >
> >     I also have had this problem. I think you should fallow what is said
ect...
> >yyou view an object more clearly as you pass through them.
> 
> To beat a dead horse ;-), what is really wanted (at least in concept) is to
> _clip_ to the perspective view volume in _3D_, then draw.  (There is
> no `behind the observer' for orthogonal projections.) This volume is the
> (infinite) double pyramid formed by projecting lines through
> the observer point to the corners of the viewport (think `screen').
 ect...
> Check out the 3D version of the Liang Barsky clipping algorithm.
> It nicely truncates 3d lines to just the viewport lobe
> of the pyramid.  Hence when you fly through objects, they
> 
> Happy landings, Gene

   Another way to do it is to transform the perspective (ie pyramid) into 
a parallel orthogonal canonical space.. clipping is extremely easy then.  Check
in Foley "Computer Graphics: Principles and Practice"  chapters 5 and 6.  Every
thing you always wanted to know about 3D projections onto a 2D view-reference-
plane.

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