🚀 go-pugleaf

bbs.brienv@tsoft.sf-bay.org (Brien Voorhees) writes:
>
>  I've been working on some graphics routines for VGA mode 13h to handle
>animating sprites while retaining the background and have managed to get
> 'em goin' pretty fast (about 25-35 fps on a 486) but that's without 
>much other overhead.  Once I add collision detection, sound, music, etc.
>I don't think I'm going to have enough cpu time to spare.

>    mov   cx,ywidth  // Set outer loop to run <ywidth> times
>rowloop:             // once per row (duh)
>    push  cx         // save what row we're on
>    mov   cx,xwidth  // Set inner loop to run for each pixel on this line
>subloop:  // There are actually two loop instructions that goto this 
>label
>    lodsb            // grab a pixel
>    cmp   al,0
>    je short itsblank  // if it's 0, skip it
>    stosb              // otherwise, write it
>    loop  subloop
>    jmp short endsubloop  // Jump outta' here. Don't wanna' fall thru to  
>                          // the other subloop section!
>itsblank:
>    inc   di              // Keep the destination index in sync
>    loop  subloop         // Ready for the next pixel
> 
>endsubloop:             
>    add   di,nextlineoffset  // Set destination pointer to proper offset 
>                             // for beginning of next image line
>    pop   cx              // Where were we?
>    loop  rowloop         // Ready for next line

loop instruction lose on '386 and better CPUs, and you're going to a bit of
trouble to use them.  The stosb instruction isn't much of a win either.
Try this:

	mov dx,ywidth
	mov bx,xwidth
loop1:
	mov cx,bx
loop2:
	lodsb
	or al,al
	je skip
	mov [es:di],al
skip:
	inc di
	dec cx
	bne loop2
	add di,nextlineoffset
	dec dx
	bne loop1

It's probably faster on 8086's too if your sprites don't have many
zero's in them.

							Ross Ridge

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