Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!agate!eos!jbm
From: jbm@eos.UUCP (Jeffrey Mulligan)
Newsgroups: comp.graphics
Subject: Re: viewing terminology
Message-ID: <2916@eos.UUCP>
Date: 16 Mar 89 03:37:43 GMT
References: <4400032@m.cs.uiuc.edu>
Organization: NASA Ames Research Center, California
Lines: 27

From article <4400032@m.cs.uiuc.edu>, by shirley@m.cs.uiuc.edu:
 
 
 
< I use the following to specify a view in my programs:
 
< lookfrom (x, y, z)
< lookat (x, y, z)
< view-up-vector (x, y, z)
< field-of-view (angle)
 
 
< This is umambiguous for a square viewport, but when the width and height
< are different, field-of-view could be left/right or up/down.  Is one
< correct, or if not, is one to be prefered?

Why not have the angle refer to the angle subtended by the diagonal of
the viewport?  This is unambiguous, although inconsistent with your
current interpretation for square viewports.  It is also consistent
with how tv screen sizes are specified.


-- 

	Jeff Mulligan (jbm@aurora.arc.nasa.gov)
	NASA/Ames Research Ctr., Mail Stop 239-3, Moffet Field CA, 94035
	(415) 694-6290