4 ms·

Strange question; why didn't many games in this era exploit this? I'd guess that the knowledge just wasn't as easily shared? Seems these systems were capable of

by tibbon 12y ago

Strange question; why didn't many games in this era exploit this? I'd guess that the knowledge just wasn't as easily shared? Seems these systems were capable of pretty amazing things, but those things were frequently overlooked.

sounds 12y ago
I think if you asked most game makers of that time, they would simply say, "You're crazy. You're planning to exploit the exact CGA chips and the exact mux and the exact nature of the monitor's response to the horizontal porch. The failure mode is that the whole screen goes wavy and maybe lets out a puff of smoke and dies. You're crazy!" But also, the reality is that the demoscene didn't even figure any of this out until 2013-ish.
sehugg 12y ago
Some did use the 160x100x16 graphics mode (using some of the same techniques in the OP) but one drawback is that they didn't always look 100% correct on clones, and some eventually broke when VGA cards came out. http://nerdlypleasures.blogspot.com/2014/09/cga-16-color-rgb-graphics-modes.html http://nerdlypleasures.blogspot.com/2014/09/cga-16-color-rgb...
- cardiffspaceman 12y ago
  My Columbia MPC clone didn't have the right character shape in the text-mode character rom, but I used the method for preview images of ray tracing code I experimented with in the '80's.
jerf 12y ago
If I'm reading correctly between the lines, they are pouring a ton of CPU into this effect. I wouldn't be surprised if you told me what we saw in the demo is literally almost all this effect can do, and there's not a lot of power left over for actually running a game. Same thing for all the things you see Commodore 64 demos do... by the time you're creating the awesome graphical effect there's often not a lot left over for the game itself. (Though there are some interesting exceptions... there appear to be some surprisingly high-quality side-scrolling platformers now based on "bad lines", which are both explained and then the platformers shown at https://www.youtube.com/watch?feature=player_detailpage&v=fe1-VVXIEh4#t=2900 https://www.youtube.com/watch?feature=player_detailpage&v=fe... . Though the entire presentation is fascinating and shows a few other demoscene effects in real programs.)
- ajenner 12y ago
  The CPU usage isn't that bad compared to some of the other things we did in the demo - with some help from interrupts it could be done with maybe 20% of CPU. There is also a much easier ~500 colour variant which doesn't take any CPU time at all once set up. I think the real reason it wasn't discovered earlier is that most CGA PCs were not connected to composite monitors or TVs (people who could afford the big expensive IBM machine could generally afford a dedicated digital monitor as well). A few games used 160x200x16 composite but even those generally had modes for RGBI monitors as well (which wouldn't work so well with the 500/1K colour modes, though I guess there are the dithering characters 0xb0 and 0xb1 which might have worked). These +HRES modes also suffer from CGA snow, which might have been a deal-breaker.
  - jerf 12y ago
    Cool, thanks for the details!
- bitwize 12y ago
  Well they were able to use the leftover CPU slop to transform, shade, and rasterize a crude 3D model in real time, so it couldn't have been all that bad...
  - ajenner 12y ago
    The 3D part used a more conventional 16-colour mode. Though it's a testament to how well Scali's code and VileR's palettes work, if they can be mistaken for the 1K colour mode!
thought_alarm 12y ago
Early games did take advantage of CGA composite color hacks to achieve 16 color graphics. E.g.: http://en.wikipedia.org/wiki/File:Microsoft_Decathlon_RGBvsComposite.png http://en.wikipedia.org/wiki/File:Microsoft_Decathlon_RGBvsC... http://en.wikipedia.org/wiki/File:KQ_CompVsRGB.png http://en.wikipedia.org/wiki/File:KQ_CompVsRGB.png However, the era of CGA composite color graphics was very short-lived. By the time the IBM-PC started to become a popular home computing platform, 16-color Tandy/EGA graphics and RGB monitors were the norm. Any composite color hacks would be rendered obsolete and unusable on these later machines.

by tibbon 12y ago

sounds 12y ago

I think if you asked most game makers of that time, they would simply say, "You're crazy. You're planning to exploit the exact CGA chips and the exact mux and the exact nature of the monitor's response to the horizontal porch. The failure mode is that the whole screen goes wavy and maybe lets out a puff of smoke and dies. You're crazy!" But also, the reality is that the demoscene didn't even figure any of this out until 2013-ish.

sehugg 12y ago

Some did use the 160x100x16 graphics mode (using some of the same techniques in the OP) but one drawback is that they didn't always look 100% correct on clones, and some eventually broke when VGA cards came out. http://nerdlypleasures.blogspot.com/2014/09/cga-16-color-rgb-graphics-modes.html http://nerdlypleasures.blogspot.com/2014/09/cga-16-color-rgb...

cardiffspaceman 12y ago
My Columbia MPC clone didn't have the right character shape in the text-mode character rom, but I used the method for preview images of ray tracing code I experimented with in the '80's.

jerf 12y ago

If I'm reading correctly between the lines, they are pouring a ton of CPU into this effect. I wouldn't be surprised if you told me what we saw in the demo is literally almost all this effect can do, and there's not a lot of power left over for actually running a game. Same thing for all the things you see Commodore 64 demos do... by the time you're creating the awesome graphical effect there's often not a lot left over for the game itself. (Though there are some interesting exceptions... there appear to be some surprisingly high-quality side-scrolling platformers now based on "bad lines", which are both explained and then the platformers shown at https://www.youtube.com/watch?feature=player_detailpage&v=fe1-VVXIEh4#t=2900 https://www.youtube.com/watch?feature=player_detailpage&v=fe... . Though the entire presentation is fascinating and shows a few other demoscene effects in real programs.)

ajenner 12y ago
The CPU usage isn't that bad compared to some of the other things we did in the demo - with some help from interrupts it could be done with maybe 20% of CPU. There is also a much easier ~500 colour variant which doesn't take any CPU time at all once set up. I think the real reason it wasn't discovered earlier is that most CGA PCs were not connected to composite monitors or TVs (people who could afford the big expensive IBM machine could generally afford a dedicated digital monitor as well). A few games used 160x200x16 composite but even those generally had modes for RGBI monitors as well (which wouldn't work so well with the 500/1K colour modes, though I guess there are the dithering characters 0xb0 and 0xb1 which might have worked). These +HRES modes also suffer from CGA snow, which might have been a deal-breaker.
- jerf 12y ago
  Cool, thanks for the details!
bitwize 12y ago
Well they were able to use the leftover CPU slop to transform, shade, and rasterize a crude 3D model in real time, so it couldn't have been all that bad...
- ajenner 12y ago
  The 3D part used a more conventional 16-colour mode. Though it's a testament to how well Scali's code and VileR's palettes work, if they can be mistaken for the 1K colour mode!

thought_alarm 12y ago

Early games did take advantage of CGA composite color hacks to achieve 16 color graphics. E.g.: http://en.wikipedia.org/wiki/File:Microsoft_Decathlon_RGBvsComposite.png http://en.wikipedia.org/wiki/File:Microsoft_Decathlon_RGBvsC... http://en.wikipedia.org/wiki/File:KQ_CompVsRGB.png http://en.wikipedia.org/wiki/File:KQ_CompVsRGB.png However, the era of CGA composite color graphics was very short-lived. By the time the IBM-PC started to become a popular home computing platform, 16-color Tandy/EGA graphics and RGB monitors were the norm. Any composite color hacks would be rendered obsolete and unusable on these later machines.