Subject: Re: [stella] 12 chars/line!? (was: re: optimizations; Call for suggestions) From: Greg Troutman <mor@xxxxxxx> Date: Wed, 24 Sep 1997 10:48:30 -0700 |
Piero Cavina wrote: > > At 16:05 +0200 23-09-1997, Eckhard Stolberg wrote: > > >>Playfield graphics for the text, variable width font to maximize how much > > ...a variable width font seems a bit too much for the 2600... :-) I thought about doing this with Dark Mage, but the cycle usage is pretty great to do more than one line per frame. The routine to load a RAM area with a new line of text would produce fairly large spaces between lines. I doubt one could preload very many lines for quick tightly spaced text with the limited RAM in a normal cart, but perhaps if SC RAM were used, ~15-20 proportional characters could be done in good resolution with the Stellar Trak method. > > >>text can be displayed. 4K standard cart should do it, no Supercharger > >>required. > > > >I don't know, if the 12 sprites text modes in Dark Mage and Bob Colbert's > >scrolling demo require SC RAM, but they would allow better output and > >more text on the screen, than a playfield routine could provide. Dark Mage does not require SC RAM, but it does use a large hunk of standard memory to build a list of pointers for each line of text (24 bytes). > > The "classic" score routine can draw 6 digits, that is 6*8=48 pixels/line. > Could it be modified to display 2x4-bits wide charachters for each digit? > > Let me explain... > > digit 1 digit 2 > 00000000001111111111... > 01234567890123456789... > > XX...X..XXX.XX...X.. > X.X..X..X...X.X.X.X.... etc etc.. > XX...X..XXX.XX..X.X. > X....X..X...X.X.X.X. > X....X..XXX.X.X..X.. > > That would allow 48/4=12 charachters per line (without flicker)! > > Can it be done? You mean a half-width font, instead of hard-coded graphics? Sure. Very problematic though. There is not enough time within the six-digit trick to read and combine the 4 bit parts into one graphics register. So, it has to be done in RAM beforehand, and that means 30 bytes for one 5 scanline high line of text. You can't very easily re-use that RAM area for drawing multiple lines of text in the same frame, because the loop that would combine 12 4-bit characters into 6 one byte graphics data, five scanlines high, would take well over a thousand cycles, I think, producing as many as 20 blank scanlines while you busily reload that RAM area... You might use VBLANK to pre-load 3 lines of text using 90 bytes of RAM if you have them (unlikely for a game, but maybe possible in some special project like Jim is doing)... Now, for a one-liner thing, like a 12-digit score, it's no big deal if you've got 30 bytes of RAM just lying (or is it laying?) around... -- mor@xxxxxxx http://www.crl.com/~mor/ -- Archives updated once/day at http://www.biglist.com/lists/stella/archives/ Unsubscribing and other info at http://www.biglist.com/lists/stella/stella.html
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