Re: A86: Tile based games
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Re: A86: Tile based games
On Thu, 18 Jun 1998 12:07:49 -0500 sampablo@juno.com (Samuel P Camp)
writes:
>
>>Anyway, since I am working on a tile based game,
>>you will in the future find tutorials on my web
>>site about tile based techniques, smooth scrolling
>>and page scrolling, and the like.
>
>
>Please help:
>I know that in order for a tile\sprite to scroll every pixel in that
>sprite must be shifted (SLA=left, SRA=right, ???=up, ???=down) to
>which ever direction that it is supposed to move, multiple times. But
>what
>about the pixels that get bumped off the sides.
>But what about the missing column?
rl shifts carry into the low bit and shifts the high bit into carry.
sla shifts 0 into the low bit and the high bit into carry
do "sla low byte, rl high byte" for each bit/pixel you want to
shift/scroll
>Is this how to scroll?
that will allow you to place a sprite not on a byte boundary, i guess
that's what you wanted.
>If it is, then how do I scroll up or down?
subtract 16 from the address for up, add 16 for down.
-josh
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