Path: utzoo!attcan!uunet!ogicse!milton!greg@walt.cc.utexas.edu From: greg@walt.cc.utexas.edu (Greg Harp) Newsgroups: sci.virtual-worlds Subject: Re: Stereoglasses, active technology Message-ID: <7613@milton.u.washington.edu> Date: 15 Sep 90 04:05:53 GMT References: <7545@milton.u.washington.edu> <7571@milton.u.washington.edu> <1990S Sender: hlab@milton.u.washington.edu Organization: The University of Texas at Austin, Austin, Texas Lines: 64 Approved: hitl@hardy.u.washington.edu In article <1990Sep14.215405.2521@santra.uucp> jmunkki@hila.hut.fi (Juri Munkki) writes: >>For these to be effective you need a computer which can alternate >>between two graphic buffers at rates quicker than 10 times a second. >>30 times a second is of course great. > >30 times per second is merely adequate. If you have any amount of >backlighting, even 30 frames per second will flicker. I wouldn't >want to use the glasses if I only had a 10 frames per second rate. > >>This is not to tough for >>displaying a left eye frame and than a right eye frame of a static >>image. If you wish to animate, you need to compute a left eye frame >>and a right eye frame and display them at the above rates. This >>is not easy. Silicon Graphics, Stardent, RS6000, and other machines >>in this class can barely do it, especially as quantity of polygons >>grows. > >If you wish to animate, you can use two frame buffers or use palette >animation to do the switching. This method guarantees that you can >switch every time your monitor does a vertical blanking, so you get >the minimum amount of flicker. You need four buffers to do double- >buffered animation in stereo. If I divide my Macintosh II screen into >4 2-bit bitplanes, I can do stereo animation with four colors. If >you have a 32-bit frame buffer with a CLUT, it is quite probable that >you can have 256 color animation in stereo. A graphics accelerator >is recommended. :-) I planned to (and forgot) to say this earlier: Why do you have to _draw_ 30 (or more) frames a second? I agree that to achieve stereo effect, the left and right images must be displayed alternately every 30th of a second. HOWEVER, what keeps you from showing one frame, say, three times? Most graphics-oriented machines can display _some_ type of image every tenth of a second. (My Amiga certainly can handle filled polygons with "smart shading" at this rate and faster with only a 68000, and many consumer-level machines can at least do half that.) In order to trick the eye, a rate of >30 frames a second (about 33) must be used. When I used an interlaced video mode on my NTSC monitor, a 30 Hz flicker is apparent at high contrast. But we must accept that most VR junkies don't have SGI's. I don't think the major breakthroughs in VR come from the people with the SGI's, DataGloves, Eyephones, etc., anyway. Certainly affordable VR doesn't come from these people. For VR to become a reality, we must build up from the bottom. > / Juri Munkki / Helsinki University of Technology / Wind / Project / > / jmunkki@hut.fi / Computing Center Macintosh Support / Surf / STORM / > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Just my $0.02... _ _ Disclaimer: "What I _really_ meant was..." AMIGA! //// //// "Don't look so frightened. This is just a passing phase -- one of _ _ //// my bad days." --Roger Waters, Pink Floyd's The Wall, One of My Turns \\\\//// \\XX// Greg Harp greg@ccwf.cc.utexas.edu Stolen from an idea by es1@cunixb.cc.columbia.edu [Ethan Solomita]: execute (Saddam_Hussein);