clh@tfic.bc.ca (Chris Hermansen) (03/22/91)
In article <3124@charon.cwi.nl> edwin@cwi.nl (Edwin Blake) writes: >In article <1991Mar6.220940.8400@nas.nasa.gov> eugene@wilbur.nas.nasa.gov (Eugene N. Miya) writes: [stuff about perspective deleted...] >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. Whoa, there - Schrodinger's cat might not agree with you on this one, let alone the existentialists among us! "Reality persists" - huh, imagine that! Anyway, in the tried-and-true fasion of changing the subject (I HAVE changed the subject line, BTW), I must cast down the gauntlet, and ask you to defend your statement that "maps are true" (never mind the bogus notions about reality). If maps are so true, then how do you explain different projections used to derive them? A UTM projection of an area will not "lie down" over an Albers; which is right? The answer, of course, is "neither". Similarly, that nice thick yellow line on my 1:200000 Michelin map labeled "D970" seldom agrees exactly with the real position of good old D970 (whatever THAT may be), and even more prosaically, the width is certainly not to scale. There's a temporal aspect to this; even if your map were an exact representation of somewhere, somewhen, sooner or later things will change, but the map won't. > >>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 Sometimes, Eugene; don't try it in Alaska with a Mercator map! > > 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). Yes, but measuring distance is not necessarily the only relevant parameter of reality that a map can represent; it's just one of the more common ones. I hope this digression proves of some value. Chris Hermansen Timberline Forest Inventory Consultants Voice: 1 604 733 0731 302 - 958 West 8th Avenue FAX: 1 604 733 0634 Vancouver B.C. CANADA clh@tfic.bc.ca V5Z 1E5 C'est ma facon de parler.
musgrave-forest@cs.yale.edu (F. Ken Musgrave) (03/26/91)
>In article <1991Mar6.220940.8400@nas.nasa.gov> eugene@wilbur.nas.nasa.gov (Eugene N. Miya) writes: > >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. From this argument it would follow that, in the practice of computer graphics, modelling is truth; rendering is lying. Draw your own conclusions. Ken -- "... this easy, indifferent sword must be chance--aye, chance, free will, and necessity--no wise incompatible--all interweavingly working together." -Herman Melville F. Kenton ("Ken") Musgrave musgrave@yale.edu (203) 432-4016
jeffry@bu-pub.bu.edu (Jeffry Nimeroff) (03/27/91)
In article <29686@cs.yale.edu>, musgrave-forest@cs.yale.edu (F. Ken Musgrave) writes: |> >In article <1991Mar6.220940.8400@nas.nasa.gov> eugene@wilbur.nas.nasa.gov (Eugene N. Miya) writes: |> > |> >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. |> |> From this argument it would follow that, in the practice of computer |> graphics, modelling is truth; rendering is lying. |> |> Draw your own conclusions. |> |> Ken |> -- |> "... this easy, indifferent sword must be chance--aye, chance, free will, |> and necessity--no wise incompatible--all interweavingly working together." |> -Herman Melville |> F. Kenton ("Ken") Musgrave musgrave@yale.edu (203) 432-4016 So radiosity is better than ray-tracing..... :-) -Jeff Nimeroff Boston University Computer Science Department soon to be... -Jeff Nimeroff University of Pennsylvania Computer and Information Sciences