Re: A86: Scrolling starfield question
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Re: A86: Scrolling starfield question
Actually the quickest way to create a good asm scrolling technique would be to
randomly fill the last bit of VIDEO_MEM
...
ld a,1
ld ($ffff),a
...
about every twenty or thirty rotates and then rotate like this (please note
this is by far not optimized..... but it works and that is what is important)
(keep reading....more at the end!!!)
...
push hl
push de
ld hl,$ffff
ld de,(VIDEO_MEM)
RotateLoop:
ld a,(hl)
rla
ld (hl),a
CompareHL_DE:
ld a,h
cp d
jr nz,SkipCompare
ld a,l
cp e
jr z,StopRotateLoop
SkipCompare:
dec hl
jr RotateLoop
StopRotateLoop:
pop de
pop hl
...
this routine rotates once, but it wraps the screen around, so stars will go
off the left side and enter on the right one pixel higher. The number of
rotates between each pixel draw (to the last bit of VIDEO_MEM) needs to be
somewhat random.... but you knew you would have to get a random number routine
already...
Hope this helps
-Tim-
honoriam2@aol.com