Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!CIS.OHIO-STATE.EDU!dnwiebe
From: dnwiebe@CIS.OHIO-STATE.EDU (Dan N Wiebe)
Newsgroups: comp.graphics
Subject: Re: World to Eye coordinate transforms
Message-ID: <8912152015.AA01911@frigate.cis.ohio-state.edu>
Date: 15 Dec 89 20:15:02 GMT
Sender: dnwiebe@tut.cis.ohio-state.edu
Lines: 19


	Is your eye at the xyz origin?  If it's not translate it there,
along with all the other points in your world space.
	Once the eyepoint is at the origin, rotate all your points so
that COI (center of interest--some point on your z' vector) is someplace
on the positive-z half of the yz plane (rotate around the y axis).  Then
rotate all your points once more around the x axis until COI lies on the
positive z axis (until z and z' coincide).  Finally, mirror in z (multiply
the z coordinate of all your points by -1).  Now, if you want a simple
parallel projection, you can just throw out your Z coordinate and plot
X and Y on the screen.  If you want perspective, you'll have to go through
a perspective transform first, shrinking the far-away stuff and stretching
the close-up stuff.  Multiplying your x and y coordinates by a something
containing a factor of 1/-z will work if you're not too picky; otherwise
you need to do a bunch of cotangent calculations.  But you probably know
all that...
	Hope this helps...

Dan Wiebe