I have -almost- finished my scrollroutine...
It scrolls in all directions and it has got a screensplit at the bottom.
It uses sprites to mask the borders and takes about 50% of your VDP-time,
but with some modifications it will probably also be possible not to use
sprites.
It is based on 8x8 patterns, and it scrolls all 16 pixels (8 seemed to be
too slow). This means that your screen will be 16 pixels smaller (240x212),
but that's not a real disadvantage.
However, one problemo...
When I set the adjust while a VDP-command is executing, there appear some
'noise'-pixels on the screen. I can avoid that to happen by exact timing of
my COPY's (execute them right after the V_BLANK-interrupt), but I would like
that different (because it will also decrease the time left for other
copies, i.e. the displaying of the character).
Does anyone know a solution for that???
For example, during the screensplit I disable the screen, and at the end I
enable it again. This however gave a white line at the lowest (second) line
of the screensplit. I was able to solve this problem by making sure the
screen was enabled during the H_BLANK-period...
Is there some solution like this for the VDP_18-problem too???
Thanks in advance,
~Grauw
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