Talk:Perspective projection

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I have removed the redirect to perspective distortion because perspective projection is not perspective distortion. It is just a term given for technically drawing a perspective, need not necessarily be distorted. All the technical explanation has to come here- picture plane, vanishing point, statonary point, etc., KRS 18:04, 10 Mar 2004 (UTC)

'Suggest you err. All perspective projection is innately distorted per article Perspective projection distortion. Also Perspective projection distortion would seem a natural sub topic of Perspective projection. Have therefore restored Perspective projection distortion.
"...in a manner that duplicates actual visual perception." This is not correct. have taken the liberty of zapping....Pat Kelso 06:51, Mar 13, 2004 (UTC)
Giving an 'illusion of depth' is not correct, isometric and axonometric views also give an illusion of depth. What distinguishes perspective is that it tries to give an effect close to actual vision(the technique duplicates the effect of light rays falling on the eye), and that is what is correct and that is what I have written. I will wait for your counterargument for a couple of days before I make the changesKRS 03:38, 14 Mar 2004 (UTC)
... And in fact, if you take a one-point perspective of an object such as a cube standing in front of it at the middle, then you can't see its third dimension at all!...So it is incorrect to say that illusion of depth is given/ produced... such a situation merely duplicates what the eye sees.
Also, since we are talking of normal visual perception of humans, that is the standard of measure... that itself cannot be termed a distortion, abnormality only exists with reference to normality KRS 14:37, 15 Mar 2004 (UTC
  • Isometric projection is just one type of "axonometric" projection. I accept your statement that axonmetrics give the illusion of depth. It shares that phenomenon with Perspective projection.

re: "Perspective projection refers to a type of technical drawing that graphically approximates on a planar(two-dimensional) surface (paper) the images of three dimensional objects so as to duplicate actual visual perception. It is sometimes also referred to as Perspective view or Perspective drawing or simply Perspective.

Please note perspective cannot both "approximate" and also "duplicate". "Approximate" is correct.

  • One point perspective may show (an illusion of) depth if the complete Horizon line appears above or below the object. In the special case where it does not, then there is no good reason for the image to be a perspective projection - unless one shows hidden (dashed) lines, in which case depth is shown again.
  • One point perspective is the only case in which the projected image might duplicate the image that the eye beholds - the case where an object, planar surface is parallel to the plane of projection and the center of the cone of vision projects from the geometric center of the object plane.
  • "...normal visual perception of humans, that is the standard of measure... that itself cannot be termed a distortion." Since we know that parallel lines do not intersect in nature but do in normal vision, I would prefer to think that the distortion obviously present lies in the eyes and not in nature (Euclid?). Pat Kelso 01:47, Mar 16, 2004 (UTC)

The accompanying graphic for this article is confusing to me, and looks like it may have been originally designed to illustrate another purpose. It seems that choosing two triangles whose points happen to be exactly coincident along the rays being drawn to the camera/eye would only be confusing to somebody who wanted to understand perspective projection. Perhaps a similar image, but of a more easily parsed 3D object (e.g. a cube or two) would be more helpful. Kjl 00:15, 4 August 2006 (UTC)

[edit] Merge proposal

Perspective projection and Perspective (graphical) seem to basically be about the same subject, I think they should be merged (i.e. take what contents is useful from the shorter one and work into the longer one), and decide which name to keep. I also did some literature search and fixed some factual errors with proper references in some of the smaller projection pages (i.e. linked from that views template) recently, so likely there's also still mistakes in the bigger articles (perspective and orthographic projection) - hopefully this can all be cleaned up eventually. --Allefant 20:36, 4 July 2007 (UTC)

Agreed. I think the [Perspective projection]] should probably just be merged & redirected into Perspective (graphical), just as linear perspective was. They all discuss the exact same thing. The "projection" template actually seems to be the main thing that Perspective projection has that Perspective (graphical) does not. The template, however, seems less important than the information that is already at the head of the article (the diagram of perspective & the table of contents). Perhaps it should be slipped into the "basic concept" section?Sir Isaac Lime 14:47, 5 July 2007 (UTC)
Yes, I think there's actually no information in the current Perspective projection text which is not already here, also the figure doesn't seem to fit the paragraph besides it. The list of concepts likely isn't that useful either as they are already used in the article (I think they all are), and that external spanish link should go away anyway. So the merge should be rather trivial. Whether or not Template:Views is really needed is another question - I'd just place it on Perspective (graphical) initially, and if it's not liked, maybe it should eventually be phased out from all articles who currently have it. --Allefant 15:21, 5 July 2007 (UTC)