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Also by Senor Barborito 02/09/2003, 8:58pm PST
Senor Barborito wrote:

Zebco Fuckface wrote:

Oh yeah, what's this commander keen clock independence thing?


From here:

some goddamn article wrote:

After a few nights of experimentation, Carmack figured out how to emulate the side-scrolling action on a PC. In the game, the screen image was drawn, or rendered, by assembling an array of 16-by-16-pixel tiles. Usually the on-screen background took over 200 of these square tiles, a blue sky tile here, a cloud tile there, and so on. Graphics for active elements, such as Mario, were then drawn on top of the background.

Any attempt to redraw the entire background every frame resulted in a game that ran too slowly, so Carmack figured out how to have to redraw only a handful of tiles every frame, speeding the game up immensely. His technique relied on a new type of graphics card that had become available, and the observation that the player's movement occurred incrementally, so most of the next frame's scenery had already been drawn.

The new graphics cards were known as Enhanced Graphics Adapter (EGA) cards. They had more on-board video memory than the earlier Color Graphics Adapter (CGA) cards and could display 16 colors at once, instead of four. For Carmack, the extra memory had two important consequences. First, while intended for a single relatively high-resolution screen image, the card's memory could hold several video screens' worth of low-resolution images, typically 300 by 200 pixels, simultaneously, good enough for video games. By pointing to different video memory addresses, the card could switch which image was being sent to the screen at around 60 times a second, allowing smooth animation without annoying flicker. Second, the card could move data around in its video memory much faster than image data could be copied from the PC's main memory to the card, eliminating a major graphics performance bottleneck.

Carmack wrote a so-called graphics display engine that exploited both properties to the full by using a technique that had been originally developed in the 1970s for scrolling over large images, such as satellite photographs. First, he assembled a complete screen in video memory, tile by tile—plus a border one tile wide [see illustration]. If the player moved one pixel in any direction, the display engine moved the origin of the image it sent to the screen by one pixel in the corresponding direction. No new tiles had to be drawn. When the player's movements finally pushed the screen image to the outer edge of a border, the engine still did not redraw most of the screen. Instead, it copied most of the existing image—the part that would remain constant—into another portion of video memory. Then it added the new tiles and moved the origin of the screen display so that it pointed to the new image .

In short, rather than having the PC redraw tens of thousands of pixels every time the player moved, the engine usually had to change only a single memory address—the one that indicated the origin of the screen image—or, at worst, draw a relatively thin strip of pixels for the new tiles. So the PC's CPU was left with plenty of time for other tasks, such as drawing and animating the game's moving platforms, hostile characters, and the other active elements with which the player interacted.

Hall and Carmack knocked up a Mario clone for the PC, which they dubbed Dangerous Dave in Copyright Infringement. But Softdisk, their employer, had no interest in publishing what were then high-end EGA games, preferring to stick with the market for CGA applications. So the nascent Id Software company went into moonlight overdrive, using the technology to create its own side-scrolling PC game called Commander Keen. When it came time to release the game, they hooked up with game publisher Scott Miller, who urged them to go with a distribution plan that was as novel as their technology: shareware.


As far as I know, this one was a clean bolt out of the blue that caught a lot of people by surprise - I can't remember if it was Sweeney or Abrash (or someone else of similar stature and relatively close relationship to Carmack) but I do know that people who would know far better than anyone here cite this as the most interesting and truly innovative thing Carmack did (the interview I read was circa Quake 2 release and Quake 3 is in many ways the least interesting thing he's done technologically speaking). Prior to this side-scrollers on the PC were insanely clunky to the point of unplayability - boom, problem solved for everyone.

--SB


So interested, I was, in the algorithm that I glossed over the bit about this being a technique for sattelite imagery.

Fortunately, this sort of serves to enhance my point while coloring me in error on a factoid that I held as an exception to it.

Hard to judge whether this is the most innovative thing he's done, then - anyone remember the vis algorithm for Ultima Underworld?

--SB
PREVIOUS NEXT REPLY QUOTE
 
Carmack's 'rocket' by Senor Barborito 02/05/2003, 5:41am PST NEW
    Re: Carmack's 'rocket' by Mischief Maker 02/05/2003, 11:58am PST NEW
    Sheesh by I need clarification 02/09/2003, 12:01am PST NEW
        Re: Sheesh by Cyrris 02/09/2003, 1:26am PST NEW
            That's telling me by I need clarification 02/09/2003, 2:11am PST NEW
        Well by Senor Barborito 02/09/2003, 6:06am PST NEW
    I don't get it! by Fussbett 02/09/2003, 1:11am PST NEW
        He's jealous. Duh. -nt- NT by Entropy Stew 02/09/2003, 3:22am PST NEW
        I'm not much of a programmer by Senor Barborito 02/09/2003, 4:58am PST NEW
            You're not much of anything by I need clarification 02/09/2003, 5:32am PST NEW
                Re: You're not much of anything by Zebco Fuckface 02/09/2003, 5:47am PST NEW
                    Re: You're not much of anything by I need clarification 02/09/2003, 6:29am PST NEW
                That's better than being unable to read by Senor Barborito 02/09/2003, 5:49am PST NEW
                    Also question for the moron by Senor Barborito 02/09/2003, 5:56am PST NEW
                        Oh, stop with the pretending you know math, already. by I need clarification 02/09/2003, 6:32am PST NEW
                    "You can't read." Brilliant. by I need clarification 02/09/2003, 6:28am PST NEW
                        Better than anything you've posted to the site, at least by Senor Barborito 02/09/2003, 12:43pm PST NEW
                            Holy crap, it just occurred to me. by I need clarification 02/09/2003, 2:31pm PST NEW
                                PS: by I need clarification 02/09/2003, 2:49pm PST NEW
                                    Hahahaha by Senor Barborito 02/09/2003, 3:18pm PST NEW
                                Thank you for proving my point. by Senor Barborito 02/09/2003, 3:17pm PST NEW
                                Tsk tsk, and you were almost making sense up until that point by Entropy Stew 02/09/2003, 4:55pm PST NEW
                                    You're both right and wrong. by Senor Barborito 02/09/2003, 5:45pm PST NEW
                                        Carmack: History's rocketeer or programmer? by Fussbett 02/09/2003, 6:08pm PST NEW
                                            Presumably by Senor Barborito 02/09/2003, 6:18pm PST NEW
                                        Also some anecdotal failures on these topics by Senor Barborito 02/09/2003, 6:16pm PST NEW
                                            Re: Also some anecdotal failures on these topics by Zebco Fuckface 02/09/2003, 7:10pm PST NEW
                                            Re: Also some anecdotal failures on these topics by Zebco Fuckface 02/09/2003, 7:13pm PST NEW
                                                Hell by Senor Barborito 02/09/2003, 8:51pm PST NEW
                                                    Also by Senor Barborito 02/09/2003, 8:58pm PST NEW
                                                        Hold up by mark 02/09/2003, 9:19pm PST NEW
                                                    Re: Hell by Zebco Fuckface 02/09/2003, 11:48pm PST NEW
                                                        Re: Hell by Senor Barborito 02/10/2003, 12:07am PST NEW
                                                            Re: Hell by Zebco Fuckface 02/11/2003, 7:08am PST NEW
                                            Lot of network talk over the past few days .. by bastage 02/09/2003, 7:48pm PST NEW
                                                Re: Lot of network talk over the past few days .. by Lufteufel 02/09/2003, 10:07pm PST NEW
                                                    Quake 1: 250-350ms ping over modem. Those were the days n/t NT by <-Nordic-> 02/11/2003, 9:48pm PST NEW
                                            Re: Also some anecdotal failures on these topics by mark 02/09/2003, 9:43pm PST NEW
                                                Re: Also some anecdotal failures on these topics by Senor Barborito 02/09/2003, 9:59pm PST NEW
                                                oops, should have read this first re: carmack [nt] NT by Lufteufel 02/09/2003, 10:08pm PST NEW
                                            Re: Also some anecdotal failures on these topics by Mysterio 11/23/2013, 6:46am PST NEW
                                                Re: Also some anecdotal failures on these topics by col.schickn 11/23/2013, 8:38am PST NEW
                                        This post should be stickied forever by This is what futurists actually bel 08/07/2017, 10:55am PDT NEW
                                            Long bets, and the futurists that love them NT by Voxels vs V-2s 08/07/2017, 3:00pm PDT NEW
                                            Rocket, stealing porn goggle tech, Futurism isn't an 'exact' science. NT by The Happiness Engine 08/08/2017, 6:26pm PDT NEW
                                    Yeah, exactly. by I need clarification 02/09/2003, 8:57pm PST NEW
                        A quick literature search by mark 02/09/2003, 1:26pm PST NEW
                            Thank you - this was exactly my point by Senor Barborito 02/09/2003, 1:49pm PST NEW
                    Re: That's better than being unable to read by Fat Autistic Fuck 06/11/2022, 12:27pm PDT NEW
            Re: I'm not much of a programmer by Zebco Fuckface 02/09/2003, 5:46am PST NEW
                Yeah, me too!! by I need clarification 02/09/2003, 6:19am PST NEW
            Re: I'm not much of a programmer by fanclub 02/10/2003, 4:36pm PST NEW
                You're right by Senor Barborito 02/10/2003, 4:45pm PST NEW
                    But I thought you wanted to weed out the imperfect... -nt- NT by Entropy Stew 02/11/2003, 1:28am PST NEW
    This whole thing. Bump. NT by Mysterio 11/22/2013, 4:57pm PST NEW
        I was going to snicker at the prediction of Doom 3 revolutionizing the industry by Lemoney Snick 11/22/2013, 7:55pm PST NEW
            Look, the technology was ready, but he was afraid he'd open a portal to hell by blackwater 11/22/2013, 10:20pm PST NEW
 
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