'Dixel' scrolling... Ghosts 'n' Goblins

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5MinuteRetro
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Re: 'Dixel' scrolling... Ghosts 'n' Goblins

Post by 5MinuteRetro » Sat Dec 09, 2017 3:18 pm


Can you tell what is what? I suppose no. Now imagine that you have such tiles and have to build a level with them in some level map editor. It's a nightmare.
The 8x8 sure looks like a confusing mess. But that's to me, not the programmer. I would've thought to the programmer these are just hex (or whatever) references that need to be called in a particular order. The programmer wouldn't be looking at the raw content of the 8x8 grids, surely?
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Wall_Axe
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Re: 'Dixel' scrolling... Ghosts 'n' Goblins

Post by Wall_Axe » Sat Dec 09, 2017 3:51 pm

the altered beast game probly has repeatable blocks that are made up of these smaller ones
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C.Born
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Re: 'Dixel' scrolling... Ghosts 'n' Goblins

Post by C.Born » Sat Dec 09, 2017 5:28 pm

Code: Select all

; your sinclair issue 19 page 74
; it stll needs a full loop

org 32000
        di
        ld bc,6144
        ld hl,22527
loop:   srl (hl)
        call c,sub1
        srl (hl)
        call c,sub2
        dec hl
        dec bc
        ld a,b
        or c
        jr nz,loop
        ei
        ret
sub1    inc hl
        set 6,(hl)
        dec hl
        ret
sub2    inc hl
        set 7,(hl)
        dec hl
        ret
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Wall_Axe
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Re: 'Dixel' scrolling... Ghosts 'n' Goblins

Post by Wall_Axe » Sat Dec 09, 2017 6:36 pm

i see the srl which i assume is the rotation
why are bits being set in the 2 subroutines though?
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Joefish
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Re: 'Dixel' scrolling... Ghosts 'n' Goblins

Post by Joefish » Sun Dec 10, 2017 12:06 am

The 'carry' bits dropping off the end of the rotations trigger bits to be set in the previously rotated byte. This method must be shockingly slow though. It must be quicker just to do two passes of a single pixel scroll!
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Wall_Axe
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Re: 'Dixel' scrolling... Ghosts 'n' Goblins

Post by Wall_Axe » Sun Dec 10, 2017 1:57 am

oops yeah

yeah you've got a call to a sub twice instead of just jumping over the set command if no pixel needs to be set

I assume the advantage of dixel techniques would be if you are storing pre-rotated bytes, you only need half the amount
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