[comp.graphics] 3-D to 2-D projection

SML108@PSUVM.BITNET (11/19/89)

Hi, does anyone out there know of a 3-D to 2-D projection equation which does
not have the effect of inverting coordinates when given a -Z coordinate such
as the equation  x(2D)=x(3d)/z(3D)*z(viewpoint) does ?

Scott Le Grand aka SML108

ksbooth@watcgl.waterloo.edu (Kelly Booth) (11/20/89)

In article <89322.172426SML108@PSUVM.BITNET> SML108@PSUVM.BITNET writes:
>Hi, does anyone out there know of a 3-D to 2-D projection equation which does
>not have the effect of inverting coordinates when given a -Z coordinate such
>as the equation  x(2D)=x(3d)/z(3D)*z(viewpoint) does ?
>
>Scott Le Grand aka SML108

Clip.

bill@hpcvlx.cv.hp.com (Bill Frolik) (11/21/89)

Can't you just add some constant offset to all your Z values
(analogous to taking a step or two back from the object you're
viewing)?  Or don't display anything that's got all negative
Z values associated with it (the object's behind you anyway);
for objects that extend from the positive Z region into the
negative Z region, just clip the negative Z value back to 
the position of the screen (probably Z=0; you only see that
portion of the object that lies in front of you).

________________________________________

Bill Frolik	Hewlett-Packard Co.
hp-pcd!bill	Corvallis, Oregon