Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!lll-winken!uunet!mcsun!hp4nl!charon!edwin From: edwin@cwi.nl (Edwin Blake) Newsgroups: comp.graphics Subject: Re: Viewer-Centered Graphics (nee Psycho-, nee Subjective-,nee Turing Test) Summary: maps != perspective Keywords: perception, perspective, maps, realism, physics Message-ID: <3124@charon.cwi.nl> Date: 7 Mar 91 09:05:12 GMT References: <3118@charon.cwi.nl> <1991Mar6.220940.8400@nas.nasa.gov> Sender: news@cwi.nl Organization: CWI, Amsterdam Lines: 32 In article <1991Mar6.220940.8400@nas.nasa.gov> eugene@wilbur.nas.nasa.gov (Eugene N. Miya) writes: >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. I think maps and perspective pictures serve very different functions. Moving, or stereo, perspective projected images are a good source of information about the world. But in terms of the title of this thread, perspective projection is viewer-centered while maps are object (or world) centered. A lot of processing is needed to turn a series of perspective images into maps. This difference was one of the reasons Plato called artists liars: the real nature of objects does not change with your point of view, reality persists, appearances change. Maps are true, pictures are lies. Computer graphics is more to do with the `lying' than the objective truth. >And look what we get from them: a little model of the world in orthogonal, >synopic view (these big words from my remote sensing classes). You can >adding the distances, figure out how long the drive tapes There are maps of Amsterdam which try to superimpose pictures of the buildings on a map of the city, this results in strange contortions to preserve the truth of the map and the conviction of the appearances. Perspective is largely thrown away and replaced by parallel projection. In the space of projected pictures it is very difficult to measure distance (no metric). Edwin Blake, edwin@cwi.nl Phone: +31 20 5924009 Centre for Mathematics and Computer Science (CWI) Department of Interactive Systems, Kruislaan 413, 1098 SJ Amsterdam, The Netherlands