At 18.55 21/08/98 -0000, you wrote:
>Thanks for the help. And not to look a gift horse in the mouth, but
>(that might seem really really weird to someone not from the US, huh? Or
>does it have international appeal? ;)...
It's very international I think, here the meaning is exactly the same :)
At 03.13 22/08/98 GMT, Erik Mooney wrote:
>I'd suggest changing the kernel so that the same
>WSYNC counts off every line of screen, as follows:
>
> ldy #0
>DoScreen:
> STA WSYNC
> ldx #0
> tay ;using Y to count scanlines
> sec ;
> sbc $80 ;A now has the distance between current line and object
> cmp #7 ;7=height of object
> bcs DontDraw ;branch if (scanline-$80)>7
> ldx #2 ;if (scanline-$80) was <= 7, enable the object
>DontDraw:
> stx ENAM0
> iny
> cpy #192
> bne DoScreen
>
>This is a decent amount more streamlined and flexible. Much easier to add
>more objects, and it's less prone to error - you're always simply counting
>lines from 0 to 191 instead of from 0 to x, eight lines to display the
>object, then 0 to 191-8-x.
Why not count backwards..:
(top of the screen)
.
.
100 let's say.. sprite height = 4; sprite y-pos=48
99 sprite must be drawn in scanlines 48,49,50,51
98
.
52 52-48 = 4 >= 4, don't draw
51 51-48 = 3 < 4, draw
50 50-48 = 2 < 4, draw
49 49-48 = 1 < 4. draw
48 <- y-pos; note: last scanline! 48-48=0 <4, draw
47 47-48 = $FF = 255 >=4, don't draw
.
.
2
1
0
(bottom of the screen )
I hope this helps. Also, remember that this technique takes a lot of
processor time, and it may be not suitable for a single scanline resolution
kernel. But please first this first.. and don't forget to study the Combat
source carefully, it's all done this way, plus the PHP trick.
Ciao,
P.
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