norlin@uokmax.ecn.uoknor.edu (Norman Lin) (06/03/91)
mmiller@isis.cs.du.edu (Mark Miller) writes: >> Some interesting trivia, but I have one correction: Atari finally DID >>release a lightpen (I used to have one). I think they did so in '84. It >>came with its own special cartridge drawing program, which was really >>quite nice (IMHO). I was impressed at the time that they hadn't merely >>repackaged Koala Paint, as they had done for the Atari Touch Tablet. >>Speaking of light pens, you can make your own: There was an article on >>the subject in a very early issue of Creative Computing (now defunct). >>It may have been 1981. Then there was the Atari Paint program, which used >>a joystick for input. >I believe I know which article you're talking about. I have that Creative >Computing issue. It is March 1983, in the "Outpost: Atari" article. It >mainly talks about how to make a home-made Atari light pen, and gives a >couple sample BASIC programs you can use with it. >What is surprising is this is an issue of Creative Computing that I just >happened to look at and pick up one day. You are the second person I have >heard refer to this article (I think you were referring to this one) after >all these years. I built this lightpen. You mention that you "just happened to look at and pick up" this issue of Creative Computing; similarly, I was browsing through back issues at the library. What was a bit annoying was that the pinouts given for the lightpen were REVERSED; this was not mentioned until a few months later in another issue. But since I was looking through back issues at the library anyway, it wasn't until about 2 years later that I happened to stumble upon that correction article, during which time the lightpen had been scrapped, rebuilt a few months later exactly as per (incorrect) instructions, failed again, scrapped, rebuilt, failed... When I finally found the correction article and got the lightpen working, though, it was less than impressive. The vertical resolution was perhaps fine enough for vertical discrimination among the 24 different graphics 0 lines; horizontal resolution was nowhere near being able to pinpoint which of the 40 columns you had the pen pointed at. And for drawing, the pen was pretty much useless. They included a sample drawing program in graphics 7. Vertical resolution was almost acceptable, but the horizontal resolution was so poor that you would get a point +/- about 40 pixels from where you were, which in graphics 7 is abysmal. The article did mention that horizontal resolution was poor, but I didn't expect it to be that poor. Did anyone else have better results with this lightpen? Ah, the days when you could build your own computer peripherals and easily interface them... what memories... >Mark Miller >mmiller@isis.cs.du.edu ---|\-#-/_|-------/|-------,*.----||---Norman Lin, University of Oklahoma---- ---|/-----|------/-|---,"--|---,"-||------norlin@uokmax.ecn.uoknor.edu------- --/|------------/-*'---|/------|--||-----(IP addr: 129.15.[20|22|24].2)------ -|/|\---/_|-----|-----------------||-"I gazed in your eyes, and saw the moon- --\|/-----|----*'-----------------||------------and the skies"---------------
Chris_F_Chiesa@cup.portal.com (06/05/91)
For what it's worth, I picked up some third-party commercial light-pen at a local user-group flea market a couple of months ago, got it to work, and had the SAME experience of totally useless horizontal resolution: "picking a pixel +/- 40 pixels away from where you were pointing" sounds about right... Must be the Atari hardware. :-(
lanmaint@nssdcb.gsfc.nasa.gov (Dave Yoest) (06/05/91)
In article <42968@cup.portal.com>, Chris_F_Chiesa@cup.portal.com writes... >For what it's worth, I picked up some third-party commercial light-pen at >a local user-group flea market a couple of months ago, got it to work, and >had the SAME experience of totally useless horizontal resolution: "picking >a pixel +/- 40 pixels away from where you were pointing" sounds about right... > >Must be the Atari hardware. :-( I don't think it's the atari hardware because I got the atari "light gun" from a friend and wrote a little c program to "shoot" at the screen machine gun style. The gun IS a light pen and seems pretty accurate (+-2 or 3 pixels) even from a distance of 15 feet away! There a small algorithm necessary to map the light pen coordinates to screen coordinates, it can be found in the technical reference manual. If anyone needs it I would be happy to look it up and post it. Also I would also be willing to post the C source for MACHINE GUN (DEEP BLUE C). It's not very good from a game standpoint, or from a C progamming standpoint (kludgey code), but it does work and could be used to test the accuracy of your light pen hardware. I also (once upon a time) had a KOALA lightpen with KOALA paint for pen. When you started KOALA for pen, it would have you "calibrate" the pen by pointing at a horizontal and then a vertical line. It also was quite accurate once calibration was completed. Dave Yoest LAN M&O Section Supervisor NASA/Goddard Space Flight Center Greenbelt, Md. USA DYOEST@128.183.43.16 DYOEST@zaphod.gsfc.nasa.gov