From: broehl@coulomb.uwaterloo.ca (Bernie Roehl) To: sci-virtual-worlds@math.uwaterloo.ca Subject: Re: REV-PROD: HMD Reviews Organization: University of Waterloo Date: Wed, 14 Dec 1994 09:44:23 -0500 In article <3clihv$kc9@nntp1.u.washington.edu>, SIR P/L wrote: >I and *sure* there's hundreds more people just like me, who are >tetering on the brink of buying one of the new HMDs... My advice: wait until the middle of next year, if you can. By then all three should be on the market (and possibly one or two others as well) and you can make your own comparisons. Anything else will inevitably be subjective. It'll also be clearer by then how much software support there'll be for each one, which is a *very* important (and possibly decisive) factor. > * Tech details (pixels, # screens, colours, CPU interface, tracking,....) They all use very similar (if not identical) 180,000-pixel LCD's; therefore, the resolution and color range will be identical. They all have two screens, one for each eye. They all have 3 DOF tracking (rotation only) using very similar sourceless tracking technology. Two of them (CyberMaxx and Virtual i/o) hook up externally, the other (Forte) has its own card. They have differing fields of view, so you get a tradeoff between field of view and image sharpness. > * Software details (what was supplied, what else can you get, how much $) Hard to say until they're all shipping. > * Programming details (Is tech prog info available? an SDK? how much ?) I can't speak for the companies, but my guess is that they'll be giving away their SDKs for free; they all need as much software support as they can muster. > * Price of HMD (eg: CyberMaxx = $799 I believe) Yes. Same for the Virtual i/o i-glasses. The VFX1 is more expensive, quoted as "under $1000". For that price you also get a CyberPuck input device, though. > * What you *think* after having bought it. Are you happy ? I haven't used all three extensively (yet). I'm most familiar with the CyberMaxx (they're the first to market) but I look forward to spending time with the others. So far, I've only used the i-glasses and the VFX1 at the Meckler conferences, for a few minutes at a time. Of course, you could just buy all three... :-) Oh, one other thing: because they're all fighting over the same market, each may try to attack the features of the others; be sure to take any rabid criticisms of any HMD with a grain of salt, since they may have originated from one of the other vendors. Caveat emptor, try before you buy, your mileage may vary, etc... -- Bernie Roehl University of Waterloo Dept of Electrical and Computer Engineering Mail: broehl@UWaterloo.ca Voice: (519) 888-4567 x 2607 [work] From randysh@pacifier.com Thu Dec 29 17:45:42 1994 Return-Path: Received: from mx5.u.washington.edu by stein2.u.washington.edu (5.65+UW94.10/UW-NDC Revision: 2.32 ) id AA18310; Thu, 29 Dec 94 17:45:42 -0800 Received: from hitl-new.hitl.washington.edu by mx5.u.washington.edu (5.65+UW94.10/UW-NDC Revision: 2.31 ) id AA25696; Thu, 29 Dec 94 17:45:41 -0800 Received: by hitl.hitl.washington.edu; id AA06588; Thu, 29 Dec 1994 17:41:59 -0800 Received: from pacifier.com by relay4.UU.NET with SMTP id QQxwlj14791; Thu, 29 Dec 1994 20:45:29 -0500 Received: (user randysh) by pacifier.com for sci-virtual-worlds@uunet.uu.net (Smail3.1.29.1 #6) id m0rNWPF-0008xKC; Thu, 29 Dec 94 17:45 PST To: sci-virtual-worlds@uunet.uu.net Path: pacifier!randysh From: randysh@pacifier.com (Randy Shedden) Newsgroups: sci.virtual-worlds Subject: Re: REV-PROD: HMD Reviews Date: 29 Dec 1994 17:45:22 -0800 Organization: Pacifier BBS, Vancouver, Wa. ((206) 693-0325) Lines: 377 Message-Id: References: <3dv178$rgg@nntp1.u.washington.edu> X-Newsreader: NN version 6.5.0 #4 (NOV) Status: OR broehl@coulomb.uwaterloo.ca (Bernie Roehl) writes: >Someone posted something to the homebrew list a while back that >discussed the whole issue in greater depth; perhaps they could re-post >it here (I thought I had saved their message, but apparently I >didn't). Here's a repost ========================================================================== Some of the following is announced figures from the manufacturers. A lot of it is guesstimations based on what little I can piece together. If anyone has any corrections or other information that will make this all make sense, please email me or the list. Randy Shedden ========================================================================== Head Mounted Display Liquid Crystal Display resolutions. by Randy Shedden (C) (November 7, 1994) With the introduction of competing Head Mounted Displays, it would seem natural that a new yardstick for comparison would be devised. The yardstick of the past for computer displays was Horizontal and Vertical count of Picture Elements. Each "PixEl" was understood to be a logical point that could be any of the available colors for that screen resolution. For the Monochrome Display Adapter, this was either Black or White. For the Color Display Adapter, this was one of four available colors. With each improved standard, this vertical and horizontal count of pixels increased as well as the number of colors available. While there are expensive monitors with higher resolution, the current consumer price point display champ is 1280 (H) by 1024 (H) with 256 colors available. Each of these pixels is actually a grouping of three color elements. The "color" is composed of varying intensities of Red, Green and Blue. This is also how TV's work. Well, a new yardstick has been devised. Consider what happened in the Video Game market. While, everyone had been using the yardstick of the MegaByte to measure a video game cartridge size, one company started using the term MegaBit. The old form of 2 MegaBytes became 16 MegaBits. Currently all video game cartridges are measured in MegaBits of storage capacity. The new yardstick of LCD resolution is a total count of RGB color triads times three because each color triad has three elements. For comparison's sake. Here is a rundown of the old and new yardstick Adapter hor. vert. colors new yardstick CGA 320 200 4 192,000 EGA 640 350 16 672,000 VGA 640 480 16 921,600 SVGA 1024 768 256 2,359,296 SVGA 1280 1024 256 3,932,160 The new yardstick is disturbing because it hides information in a seemingly large number. If you are given just the new yardstick number, you can use formulas to work back to a ballpark figure of the old familiar yardsticks you have come to know and love. Ideal horizontal:vertical resolutions have an aspect ratio of 4:3 because of the shape of the monitor. Monitors (including TVs) have a aspect ratio of 4:3. Let's double-check this. CGA: 320/ 200 = 1.6 (not 4:3) EGA: 640/ 350 = 1.83~ (not 4:3) VGA: 640/ 480 = 1.3~ (4:3) SVGA: 1024/ 768 = 1.3~ (4:3) SVGA: 1280/1024 = 1.25 (not 4:3) As you can see, resolutions vary, but they try to stay near 4:3 aspect ratio (H/V = 4/3 = 1.3~) Using this information, we can assume that H / V = 4 / 3, SO H = V * 4 / 3 So the new yardstick formula becomes H * V * 3 = new yardstick H * V = (new yardstick) / 3 (V * 4 / 3) * V = (new yardstick) / 3 V * V = (new yardstick) / 4 V = SQRT(new yardstick) / 2 Let's try this out. Assume we are given a new yardstick of 120,000 (for example). V = SQRT(120,000) / 2 = 173 H = V * 4 / 3 = 173 * 4 / 3 = 231. Of course, if the aspect ratio isn't 4:3, then the only thing that these numbers have in common with the real numbers is that their product is one-third of the new yardstick number. Assume that you know the horizontal and vertical resolution in terms of individual RGB color elements. You then know that the product of these two numbers is the new yardstick number (120,000 in our example). So, NH (the new horizontal resolution number) and NV (the new vertical resolution number) NH * NV = 120,000 But how to you get from NH and NV to H and V. The screen can be represented by the following picture R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G This is a 30 pixel by 12 pixel screen, but the RGB color triad count is represented by each of the R G B color triad groupings. However, if we don't move the B pixels on the top row to a position below the bottom row, we will have unused B pixels on the top and unused R and G pixels on the bottom. R G R G R G R G R G R G R G R G R G R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B B B B B B B B B B So, if we just count the R pixels and designate those as the center of the RGB color triad grouping (the spacing between Rs is the same as the spacing between RGB centers), this becomes R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R Now we could refer to this as a 10 RGB color triad by 12 RGB color triad resolution, but the number of distinct columns is higher than that. It makes more sense to refer to this as 6 rows of a staggered line, that looks like this R R R R R R R R R R R R R R R R R R R R Now that we have assumed that for every two rows of "pixels" we have one row of RGB color triads, we have V = NV / 2 Now how do we solve for H. 1) NH * NV = new yardstick 2) H * V * 3 = new yardstick 3) H * V * 3 = NH * NV 4) H * (NV / 2) * 3 = NH * NV 5) H / 2 * 3 = NH (the NV's cancelled each other) 6) H = NH * 2 / 3 So, the formula becomes H = NH * 2 / 3 V = NV / 2 This makes the resolution 30 * 2 / 3 by 12 / 2 OR 20 triads by 6 triads. HOW THE PREVIOUS FORMULAS APPLY TO THE 120,000 CYBERMAXX LCD >From the CyberMaxx Developer's Manual, we now that NH = 505 "pixels" NV = 230 "pixels" (Note that the product of 505 and 230 is 116,150 and NOT 120,000) H = NH * 2 / 3 = 505 * 2 / 3 = 1010 / 3 = 337~ RGB color triads V = NV / 2 = 230 / 2 = 115 RGB color triads. Notice that the ratio of the LCD is not 4:3. In fact, it is 337/115 = 2.93 (almost 3:1) HOW THE PREVIOUS FORMULAS MIGHT APPLY TO THE ANNOUNCED 180,000 CYBERMAXX LCD Since there is no other information available on this, let's assume that the same horizontal:vertical ratio is kept. H * V * 3 = 180,000 H * V = 60,000 H / V = 2.93 H = V * 2.93 (V * 2.93) * V = 60,000 V * V = 60,000 / 2.93 V = SQRT(60,000/2.93) = 143 H = 143 * 2.93 = 419 So, It might have a 419 (H) by 143 (V) RGB color triad resolution. HOW THE PREVIOUS FORMULAS APPLY TO THE STUNTMASTER LCD The StuntMaster LCD has a 240 (H) by 86 (V) RGB color triad resolution. If we want to find the new yardstick figure, use the formula new yardstick = H * V * 3 new yardstick = 240 * 86 * 3 = 61,920. If we want to find the new horizontal figure, use the formula NH = H * 3 / 2 NH = 240 * 3 / 3 = 360 If we want to find the new vertical figure, use the formula NV = V * 2 NV = 86 * 2 = 172 Let's double-check NH * NV = new yardstick 360 * 86 = 61,920 Yes, it checks out. HOW THE STUNTMASTER AND THE 120,000 CYBERMAX LCDS COMPARE For comparison sake, the VictorMaxx StuntMaster has a RGB color triad resolution of 240 (H) by 86 (V). The CyberMaxx 120,000 resolution is a 40% increase in the horizontal resolution and a 34% increase in the vertical resolution over the StuntMaster. Just to double check our figures, let's work backwards. The StuntMaster has a 240 (H) by 86 (V) RGB color triad resolution. Using the reverse of the formula above, we find it has a 240 * 3/2 = 360 (H) and a 86 * 2 = 172 (V) "pixel" resolution. Again we find a 40% ((505 - 360)/360) horizontal increase and a 34% ((230 - 172)/172) vertical increase. This close corralation between "pixel" horizontal and vertical increases and RGB color triad horizontal and vertical increases lead me to a high confidence level in the figures below. 337~ (H) by 115 (V) RGB color triad resolution for the 120,000 LCDs. Since the StuntMaster would be classified as a 61,920 pixel resolution LCD, I'm not sure if you would round to 60,000 or round up to 70,000. When asked about how the CyberMaxx compares with the StuntMaster in resolution, I'm sure some marketing types will say that the resolution has been "doubled". 120,000 compared to 60,000. In actuality, the figure is 116,150/61,920 or 188% increase in RGB pixels. HOW THE PREVIOUS FORMULAS APPLY TO THE PERSONAL DISPLAY SYSTEMS The announced "pixel" count is 138,000. H * V * 3 = 138,000 H * V = 46,000 If the aspect ratio is 4:3, then it follows H / V = 4 / 3 H = V * 4 / 3 (V * 4 / 3) * V = 46,000 V * V = 46,000 * 3 / 4 V = SQRT(46,000 * 3 / 4) = 186~ H = 186 * 4 / 3 = 248 So, It might have a 248 (H) by 186 (V) RGB color triad resolution. If the aspect ratio is 3:1 (like CyberMaxx), then it follows H / V = 3 / 1 H = V * 3 (V * 3) * V = 46,000 V * V = 46,000 / 3 V = SQRT(46,000 / 3) = 124~ H = 124 * 3 = 372 So, It might have a 372 (H) by 124 (V) RGB color triad resolution. HOW THE PREVIOUS FORMULAS APPLY TO THE PERSONAL DISPLAY SYSTEMS "GAMER" The announced "pixel" count is 104,000. I won't bore you with the math this time, suffice it to say that If aspect ratio is 4:3, we have a RGB color triad resolution of 215~ by 161~. If aspect ratio is 3:1, we have a RGB color triad resolution of 321~ by 107~. CONCLUSION. I find the new yardstick for HMD LCDs to be a very confusing subject. It seems obvious to me to be another in the round of marketing numbers games. I hope that it will not continue to be practiced by HMD manufacturers. I fear that they will all adopt the practice to stay competitive. What I would like to see is the resolution announced in terms of RGB color triad horizontal and vertical figures. Toward that end, I have created the following chart Product LCDs Horiz. Vert. Aspect Ratio Most MS-DOS VGA games 1 320 240 1.3~ (4:3) StuntMaster LCD 1 240 86 2.8~ PDS "Gamer" LCD 1 215 161 assuming aspect ratio of 4:3 PDS "Gamer" LCD 1 321 107 assuming aspect ratio of 3:1 CyberMaxx 120,000 LCD 2 337 115 2.9~ CyberMaxx 180,000 LCD 2 419 143 2.9~ PDS i-glasses LCD 2 248 186 assuming aspect ratio of 4:3 PDS i-glasses LCD 2 372 124 assuming aspect ratio of 3:1 VFX-1 2 428 244 1.8~ (7:4) (1) Most MS-DOS VGA games, StuntMaster, and VFX-1 are firm RGB color triad resolution figures. (2) CyberMaxx 120,000 LCD figures are calculated from announced information (3) CyberMaxx 180,000 LCD figures are extrapolated from 120,000 information (4) PDS figures are all based on the only announced information. The new yardstick count of all pixels. These figures are just guestimates. Randy Shedden -- Randy Shedden