Screenmode questions


@jonne wikipedia article speak about 3d rendering engine. Not sure if it’s the tile mode you want to implement in pokitto.



Hmm. Can’t find decent articles

Goes sumthing like this:


Yeah, I read the docs. As far as I can tell it was mostly used for art and only occaisionally used for proper games. That and the C64 could (as far as I can tell) change screen mode while running so it could e.g. do the titlescreen using the multicolour mode and run the game itself in a different mode.

I could be wrong though, I only skimmed the docs because I’ve been busy today.


That article just reminded me of the SNES’s infamous Mode 7 and its GBA revival.


I don’t think that I am following the conversation fully. is @Pharap suggesting that tiled gfx modes on old systems was used mostly for still images and not ingame graphics? Is so, then nothing could be further from the truth. Tile modes were used for everything in the old days, not only that, it was the ONLY way for a lot of console/computers.
As for the C64 changing screen modes, not only could it do that between updates, it could do it during updates also, so the top half could be 1bpp 320 pixels wide, then a section could be 2bpp 160 pixels wide both at the same time. This effect was used a lot to show scores and other info using hi resolution text on a low resolution background.


It is the only way to do full screen graphics on a RAM limited system.

For example Maniac Mansion was done this way.

I need to show you guys how it works / find better articles on the topic.


If you search “C64 multicolour bitmap” the vast majority of results are showing off art rather than gameplay. There’s one or two adventure stories/point & clicks, but most of the focus seems to be on art.
I mean that C64 mode specifically, not tile modes in general.
I don’t know if that’s just because there’s some odd C64-themed art culture on the internet, but to paraphrase Darth Vader: I find the lack of game screenshots disturbing.

I know the extent of the use of tile modes in old consoles, I’ve dabbled a bit in NES, SNES and GBA emulation.

I brought up the dynamic screen mode changing to highlight the fact the Pokitto won’t do that, the screen mode is selected at compile time and then you’re stuck with it for the whole game. Those are exactly the kinds of cool tricks you won’t be able to do. Perhaps C64’s MCB mode is easier to use than it sounds, but going by what I’ve found about it I suspect it would mainly be used for point & clicks or adventure games.


Nah, almost all c64 games used mono or multicolour tiled modes. C64 multicolour bitmap used the screen as an actual bitmapped image, allowing indevidual pixels to be set at any time, rather than a full tile. Yes, bitmap mode would be used rarely as it would eat up a huge chunk of ram, What I initially meant would be a multicolour tiled mode, which would basically be a mono tiled mode, with a second tile buffer denoting how the 8x8 tiles would be displayed.
This explaines a little better than I am…


@spinal: I believe this was the original idea behind tiled mode (when we were working on the roguelike). Have 1bit sprites and assign a color to them. I think we were just working on black + 1 color, but I bet some code wizards here can make it possible to assign colors to both color 0 and 1.

I know both @adekto and @jonne were working on it, but we settled for a different mode to go with the CGA jam’s palette requirements.


@vonbednar that sounds like the ZX spectrum, a high res (for then!) 1 bit screen (256*192)
and an overlayed ‘attribute’ for each 8x8 block which contained 2 colours, paper and Ink. (background/foreground)

that would be quite a cool retro mode, especially to do the famous ‘attribute clash’ that the spectrum was famous for :slight_smile:

oddly, i’ve been trying to fake this restriction using modern shaders but it would be cool to be doing it properly on the hardware of the pokitto!


Ah, I thought you meant multicolour bitmap mode as opposed to multicolour tiled mode (which is called muliticolour character mode on the C64).


So in theory, would something like game boy colour tiles be possible. Having a 2bpp tiles and assigning a palette to them separately?


In terms of tile modes with 4 bits per pixel the best options are probably either:

  • 2 bit colour select, 2 bit palette select (4 colours, 4 palettes)
  • 3 bit colour select 1 bit palette select (8 colours, 2 palettes)

Or, you could have 8bits per two pixels and have them share a palette, which would grant you 3 colours per pixel and 4 palettes, but that might be getting a bit too complicated.