Thomas Jentzsch wrote:
> > 1 - assimilated all of Thomas' superior knowledge and put it
> > straight into the kernel
> Well, you almost did, but i think it's my fault. I'll try to exlain my tip #3 by example.
I tried my best :-)
> tya
> ; CLC ; i think you already eliminated this
> SBC verPos
> ADC #$13
> BCC SkipDraw
> LDA (playerpointer),Y
> STA GRP0
> ...
> dey
> BNE nextLine
> Notice that i didn't change Y, i'm directly using the line counting value. You "just" have to change the pointer variables and realign your data ;-)
> The example only saves 2 cylces (you're doing this twice), but it frees X for something else.
Ok I try again to fully understand you this time.
During VBlank for example I'd say playerpointer = shapestartoffset -
verPos, right?
And since verPos might have values from $C0-$13 (or $60-$14 in a 2LK),
all my shape data has to start higher than $C0 ($60) in the data pages.
Did I get it this time? :-)
Brilliant - again! Having X back is very valuable, even more than the
cycles :-)
> For your missile problem, i'd suggest the following trick, which can be found in the Combat listing:
Guess _which_ source I started to read yesterday? :-)
> ldx #ENAM1
> txs
> ...
> cpy M0line
> php
> cpy M1line
> php
> You can use this for the ball too.
Unfortunately my missiles need to be higher than a line, but I can use
this definitely for the ball.
I found something very interesting regarding quick/clever missile
enabling/disabling in the archive:
http://www.biglist.com/lists/stella/archives/199704/msg00056.html
I goes like this:
Do this before the display loop:
LDX #$1E ;for ENAM1 - could also be used for ENABL or ENAM0
TXS
And in the loop:
LDA MissileY
SEC
SBC Scanline ;A has (MissileY - Scanline). If it is >=0 but <4,
;we want the carry clear.
CLC
ADC #252 ;If 0 <= A <= 3, the carry will now be clear.
LDA #00
ADC #00 ;If the carry was clear, A now = 0, so Z is set.
PHP ;Plug it into ENABL.
I think it can be optimised here & there. Besides the carry especially
the last part. Wouldn't...
ROL
ROL
PHP
...do the the trick way shorter & quicker than
LDA #00
ADC #00 ;If the carry was clear, A now = 0, so Z is set.
PHP ;Plug it into ENABL.
????
But still... wouldn't it be best to make the missile yellow like the
background, where there is no gun? The only other object actually
crossing that *invisible* missile would be the ball. Can't the ball just
have a higher priority than the misslie?
Greetings,
Manuel
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