Path: utzoo!news-server.csri.toronto.edu!rutgers!usc!elroy.jpl.nasa.gov!jarthur!ucivax!honig From: honig@ics.uci.edu (David Honig) Newsgroups: comp.graphics Subject: Re: Viewer-Centered Graphics (nee Psycho-, nee Subjective-,nee Turing Test) Summary: notes on terminology: binoc disparity .ne. perspective projection Keywords: perception, perspective, Leonardo, realism, physics Message-ID: <27DAA30E.20679@ics.uci.edu> Date: 10 Mar 91 21:20:14 GMT References: <3118@charon.cwi.nl> <1991Mar6.220940.8400@nas.nasa.gov> Reply-To: honig@ics.uci.edu (David Honig) Organization: UC Irvine Department of ICS Lines: 33 In article <1991Mar6.220940.8400@nas.nasa.gov> eugene@wilbur.nas.nasa.gov (Eugene N. Miya) writes: >On a long drive back from the Sierra, I pondered this topic more. >Perspective does have uses. This is how we make maps, topographic maps, >and other maps. Is there any image more pervasive and full of more >useful information than a map? I don't think so. In the vision literature at least, perspective projection means something entyirely different from binocular stereo. Binoc stereo is used to make maps from images taken at two different positions, either two eyes on either side of a nose or a moving 'plane. Perspective projection, as opposed to orthographic (parallel) projection, (the fisheye effect more pronounced with short focal-length lenses) doesn't give ranges to objects unless the object's true size is known. Then, the fact that under perspective projection, the apparent (projected) size is inversely proportional to its distance can yield distance. You can look at stereopairs that are generated with parallel (not perspective) projection. And you can look at perspective images monocularly. They are separate issues. ******************** On a separate issue related to Eugene's comments about the information in maps, take a look at Edward Tufte's recent books on displaying quantitative information. They explain what makes a good graphic objectively and are excellent reading. -- David A. Honig Quotas are for files, not people.