Posted By
Murphy
on 2018-09-01
18:04:34
|  Re: AGSP
Gaia: There is a problem with LineCrunching. You can increase the char pointer by one row in every pixel row. So you lost a 24 pixel high area on the top of the screen if you want upscroll the char pointer by 24 line.
On the Pinball Dreams C64 they put sprites to that area.
https://www.youtube.com/watch?v=NgcSN6e68jA
On C64 the only know solution to overcome this limitation is several precalculated colormap and bitmap (started from the first char row, started from the 6th char row, started from the 12th char row...). They scroll up to 5 line with LineCrunch and after the 6th line they switch the bitmap to the next one.
Clarence used this trick in the Rocketry.
https://youtu.be/yCxDzq0rFGo?t=1m39s
We have hardware scroll register for the bitmap, so only the precalculated colormaps required on plus/4.
But very hard to manage this on a game.
Maybe I found another solution. If you extend the screen height to 28 char, but you used the first 3 char row only for the LineCrunching you get a vertically moveable 25 char height screen. Maybe :) I've never tried this before.
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