kenjennings

Are you done yet? Anything more?

Super kewl. I was not aware of that. There's always another trick.

I don't completely understand this question. The multi-plexing point suggests to me this question pre-supposes the capabilities of some other non-Atari, computer graphics hardware. ( ? ) Do you simply mean page flipping between two screens for each video frame? This would be easy to do on the Atari, but it could also be done on any other computer that can monitor frame start, and switch screen registers/pointers. The end result is simply the math of how many colors are present on each separate screen. That math would multiply out the colors the same way on any computer that supports the page flipping method.

Most of the time the palette is 128 colors, 8 shades of each base color. Using the GTIA option for 16 shades of one color, and interrupts to change the base color at different locations on the screen this becomes a possible 256 colors.

The Atari hardware has several things than can be combined that can add/vary colors, so the simple answer to this is "it depends". The "Per Scanline" designation is important here, because all color options, and even graphics modes can be changed on each scan line. Few games use only a full screen of a single graphics mode. Multiple graphics modes mixed on screen is the norm. Also, for the sake of the question this answer covers only what can be done strictly through inherent hardware capabilities that once set up requires no further CPU support to maintain. First, is the "normal" 14 graphics modes. Depending on the display mode there could be two, or four, or five colors (per scanline). However, Player/Missile graphics are separate color registers from the playfield and can add four more colors to this, so there could be up to nine colors (per scanline). The Atari has nine color registers, so this would be the limit of colors created purely by color indirection (using the color registers.) (per scan line). BUT, different GTIA options provide other color interpretation possibilities beyond the "normal" modes. This allows 9 colors as playfield graphics (using color registers), or 16 colors (all the same brightness), or 16 shades of one single color. So, the answer can be sixteen colors (per scanline). HOWEVER, (there's always some other trick going on the Atari) color merging options in GTIA can mix playfield and player/missile graphics colors together, and the total number of colors possible doing this is 23 colors. Nine of those come from color registers. The rest of the colors are done by overlapping Player/Missile objects with each other and overlapping Playfield pixels with Player/Missiles pixels. This would be a fairly contrived situation and has limitations, but it is do-able, and it is an inherent capability of the hardware. So, the complete answer is the hardware can produce up to 23 colors (per scan line).

Right, the marketing stuff was never very accurate about what the machine could actually do. In the marketing war with Commodore they let Commodore get away with saying the Atari could only display 192 scan lines. Atari never weaponized the fact of the built-in horizontal/vertical overscan capability :-).

There's tons of information about the hardware here on the Altirra site: http://www.virtualdub.org/altirra.html And the Altirra hardware reference manual: www.virtualdub.org/downloads/Altirra%20Hardware%20Reference%20Manual.pdf And wikipedia has pretty much the same info... https://en.wikipedia.org/wiki/CTIA_and_GTIA https://en.wikipedia.org/wiki/ANTIC

Six text modes (ANTIC 2 through 7) Eight Map modes (ANTIC 8 through F) So, 14 graphics modes. Then there are four possible color interpretations by GTIA. 14 * 4 == 56 graphics modes. Though many of these combinations may not have a practical use. So, so somewhere in the ballpark of 17 "easy to use modes" (the base 14 modes plus 3 GTIA color interpretations on mode F ) up to around 20 to 26 usable configurations depending on your creativity. Not including DLI gymnastics that game vertical scrolling to cut down text mode heights or to stretch map modes.

Mine seems to be superglued or outright melted closed. If I had extra copies of this cart and was curious I'd try carefully scoring the side seams with a boxcutter, hopefully without stabbing myself or removing useful fingers.

You're far too generous with your praise. Thanks. There is only one lousy sprite in the game. I don't think it will get much better than it is right now in the sound department. I'm not much for programming audio. The original game was written in 1983 for the CBM Pet by someone in high school with not a lot of programming experience and he did an altogether stand up job on it considering the limitations.

THANKS! Weeeell. Learned something new... Between Altirra, Atari800, and PAL equipment out of the five possible blues looks like there's only two that do appear as blue for everyone. huh. Shame. I was rather attached to Aqua. Also, I forgot I was using artifact colors to make green labels for the score lines. (Residue left over from Version 2 of the game based on ANTIC text mode 2.) Now that I think about it the way I set up the characters I should be using ANTIC text mode 4 for those lines, too, and get the color result I was looking for. (Derp. Head slap.) THANKS AGAIN!

Hi lo. Would someone with real equipment like to playtest something for me? My Ataris are at the bottom of the keep the wife or keep the Atari closet. https://github.com/kenjennings/Atari-Pet-Frogger/tree/master/Frogger03 Run the Frogger03.xex. Let me know if the Title and Game displays are stable on real hardware, and no goofy flickering or dancing DLIs. It seems to be working OK on Atari800 and Altirra emulators. The game is only set for one life to make it faster to trigger the game over display. Yes, I know the graphic on the Game Over display is incomplete. Yes, the sound is very lame. Thanks.

Well, now, this is weird. I tried this on the new Atari 800 emulator, and the mouse-as-a-touch-tablet feature is working like the virtual tablet is upside down. Weird. It worked fine in older versions.

I'm having a problem with GTIA artifacts. Running 4.1.0 on linux, opensuse 15.0. After setup and configuration for GTIA I'm getting the blue/red artifacts from a program I wrote. Same program on atari800 3.x on linux does the green/purple artifacts. Same program on Altirra in Windows is getting green/purple artifacts. Is there some hidden voodoo in the config file to coerce this?

Ranger03: Some simple utilities in assembly language for Atari BASIC: http://atariage.com/forums/blog/576/entry-13175-part-1-of-11-simple-assembly-for-atari-basic-introduction/