RE: [stella] FlipDraw...

Subject: RE: [stella] FlipDraw...
From: "Fred Quimby" <c9r@xxxxxxxxxxx>
Date: Thu, 11 Aug 2005 22:06:04 -0400
More comments about Flipdraw and why it's nice:

1.  You do not need to set a pointer every time you move your sprite.  
Actually, you only need to set it once.
2.  Graphics data need not be aligned carefully - no more worries about 
wrapping page boundaries for the whole vertical range of the sprite.  As 
long as the graphics data itself doesn't cross a page boundary, it will 
3.  If you aren't animating your sprites, I think you could use absolute 
indexed addressing for your sprite data and save a cycle and two bytes of 

>FWIW, the Alpha 0.1 and 0.2 bB kernel uses this too, mostly because of the
>pointer setup thing.  However, I will probably use a kernel rewritten with
>skip/switchdraw to get more on the screen, but I'm not looking forward to
>the pointer setup stuff.  Actually, I haven't figured out how to setup the
>pointers at all yet...
> >Hi there!
> >
> >How about...
> >
> >      DCP spriteOffset
> >      BCC FlipDraw
> >      LDY spriteOffset
> >      LDA (spritePtr),Y
> >Continue
> >      STA GRP0
> >
> >That's 2/3 cycles more than skip/switchdraw, but it neither requires a
> >line counter (save lotsa cycles here!) nor occupies a register.
> >
> >I'm currently working on a 4LK with 2LK sprites, and this seems to be by
> >far the most elegant way to do that :-)
> >
> >Also instead of the nightmarrish sprite/pointer setup for skip/switchdraw
> >it only requires a setup as simple as:
> >
> >      LDA spriteY
> >      STA spriteOffset
> >      SET_POINTER spritePtr, spritedata
> >
> >Greetings,
> >Manuel
> >Archives (includes files) at 
> >Unsub & more at
> >
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