From albanycs!leah:rsb584 Thu Jan 28 01:24:20 1988 Received: by albanycs.albany.edu (5.54/4.8) id AA18991; Wed, 27 Jan 88 09:33:38 EST Date: Wed, 27 Jan 88 09:33:35 EST From: albanycs!leah:rsb584 (Raymond S Brand) Received: by leah.Albany.EDU (5.58/1.1) id AA23806; Wed, 27 Jan 88 09:33:35 EST Message-Id: <8801271433.AA23806@leah.Albany.EDU> To: albanycs:beowulf!rsbx >From ewhac@well.UUCP Mon Jan 25 04:02:44 1988 Path: leah!itsgw!nysernic!rutgers!rochester!bbn!uwmcsd1!ig!agate!ucbvax!hplabs!well!ewhac From: ewhac@well.UUCP (Leo 'Bols Ewhac' Schwab) Newsgroups: comp.graphics Subject: Re: Interactive Stereo Viewing Message-ID: <5063@well.UUCP> Date: 25 Jan 88 09:02:44 GMT References: <4615@tut.cis.ohio-state.edu> <146@rocky8.rockefeller.edu> <1396@pixar.UUCP> <5039@well.UUCP> <3005@watcgl.waterloo.edu> Reply-To: ewhac@well.UUCP (Leo 'Bols Ewhac' Schwab) Organization: Lt. Col. Oliver North, Overseas Shipping and Receiving. Lines: 102 First, some clarifications. I was working on a project to bring a piece of 3D technology to the consumer market. It never materialized. Howver, in the process, I spent about four months playing around with 3D on the Amiga under the tutelage of Michael Starks, who I am led to believe is one of the top five experts on 3D on the planet. He had at least three bookcases full of nothing but copies of patents on 3D processes from all over the world. And he's read all of them. He knows what looks good and what looks bad. After fiddling around for some time, I managed to get images which he pronounced as good-looking. Based solely on that, I presented my methods of achieving 3D. I never meant to imply that the gentleman from Pixar was totally wrong, but his approach seemed block-box-ish and non-intuitive. So I thought I'd present my approaches which, according to Michael, are the correct ways to go about things, and which I felt de-mystified things a bit. Keep in mind that there may be other approaches I don't know about. In article <3005@watcgl.waterloo.edu> drforsey@watcgl.waterloo.edu (Dave Forsey) writes: >By aiming the two cameras have you not forced the viewer to focus on >one specific part of the screen? If the viewers actual focus wanders >to another part of the CRT, won't the visual information presented to >each eye be incorrect? When viewing a 3D still or movie, the centre of >attention may wander all over the screen, not just the part that the >cameraman has decided to focus on. > This point has crossed my mind, too. Again, you should consider the human vision system. When looking at an object, your eyes converge to focus on that object. Your center of attention is focused on that one spot, and all other areas are more or less ignored. When the viewer wishes to shift his/her attention, the eyes refocus and re-converge on a different section of the world. This happens automatically. Hold a pencil at arm's length from you, and stare at a spot on a wall beyond the pencil. Notice that you see two images of the pencil when focused on the wall. Now focus on the pencil. Note that there are now two images of the spot on the wall, because your two eyes have reconverged. In either case, was the 3D effect diminished? By selecting the point of convergence, you are merely selecting which object will appear at the surface of the screen. The 3D effect will be no less striking, and if the viewer wishes to shift their attention, they simply refocus. If you were to shoot a scene in parallel, the convergence point would be at infinity, and everything in front of infinity (i.e. everything) would appear to leap off the screen. This is not always desireable. In article <20092@bbn.COM> cosell@bbn.com.UUCP (Bernie Cosell) writes: >I think that the current formulations (and transform matrices, etc) for >generating stereo pairs have it a bit wrong. You should **NOT** >converge the two views you generate -- they should be from offset >perspective origins to be sure, but the two primary sight axes should >be _parallel_. [ ... ] > >From "The world of 3D, a practical guide to stereo photography" by >J G Ferwerda: > Those without much experience with stereo often think that the lens > axes while shooting the left and right image, should be trained somewhat > `towards each other'. For instance, while shooting a flowering shrub > at a distance of 3 m, it seems obvious that in both cases a certain > flower should be kept in the centre of the viewfinder for each shot. > However, this is not the case. Even if the subject that is to be taken > is very near -- especially then -- the lens axes should not be > trained `towards each other'. > With all due respect, I feel that your source is very wrong, particularly with objects that are less than 1m away. Consider a flower that is six inches away from a 3D camera, with lenses 2.5 inches apart. If you develop the photos, you'll find the left eye photo is heavily clipped against the right side of the photo border, while the converse is true for the right image. Your eyes would need to cross very severely to see this image, which is uncomfortable, and it would also try to leap to your nose. However, since the images are clipped against the photos' edges, your brain gets confused, and the 3D effect is lost almost completely. Portions of the image that try to leap off the viewing media should be done very carefully. They should not be clipped against any edges. Parallaxes should be kept to a minimum, even if you've got an enormous screen. You don't need to hit the viewer over the head with 3D. You can be subtle, and still come off very well. An offshoot of the project I worked on should be appearing on the market for the Amiga Real Soon Now. Part of the package will be some images I digitized, using converging cameras, as well as an image created using Deluxe Paint II (an Amiga paint package). I think they look rather good, but then I'm biased.... _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_ Leo L. Schwab -- The Guy in The Cape ihnp4!ptsfa -\ \_ -_ Recumbent Bikes: dual ---> !{well,unicom}!ewhac O----^o The Only Way To Fly. hplabs / (pronounced "AE-wack") "Simplicity and clarity should be your theme in dress." -- A fortune cookie I got in LA's Atomic Cafe.