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42% faster HGR per-pixel fizzle fade

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4am 2020-09-03 14:16:54 -04:00
parent 8c98fbf544
commit 6ae0509874
1 changed files with 41 additions and 42 deletions
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83
src/fx/fx.hgr.1bit.fizzle.a
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@ -5,51 +5,39 @@
!to "build/FX/BIT.FIZZLE",plain
*=$6000
copymask=$ff
rnd1=$fe
rnd2=$ff
;init RNG
ldx #1
stx @rnd1+1
dex
stx @rnd2+1
ldy #1
sty rnd1
dey
sty rnd2
;iterate
@loop
ldy @rnd1+1
ldx @rnd2+1
lsr @rnd2+1
ror @rnd1+1
lda rnd1
eor #$ff
sta $26
sta $3c
ldx rnd2
lsr rnd2
ror rnd1
bcc +
;feedback polynomial forms #$8016 for period of 65535
lda @rnd1+1
lda rnd1
eor #$16
sta @rnd1+1
lda @rnd2+1
sta rnd1
lda rnd2
eor #$80
sta @rnd2+1
sta rnd2
;little hack to avoid missing offset zero
;screen hole at $xxFF is missed instead
+ tya
eor #$ff
sta $26
sta $3c
lda #%00000001
sta copymask
+
txa
and #$e0
beq +
- asl copymask
adc #$e0
bne -
+ txa
and #$1f
;target page 1
@ -61,25 +49,36 @@ copymask=$ff
;copy pixel from other page to this page
ldy #0
lda ($26), y
eor ($3c), y ; merge source and destination bits
and @copymasks, x ; isolate the bits to replace, zero the rest
eor ($26), y ; unmerge source and destination bits, leaves "to keep" destination bits intact
sta ($26), y ; write the result
lda ($26),y
eor ($3c),y ; merge source and destination bits
and copymask ; isolate the bits to replace, zero the rest
eor ($26),y ; unmerge source and destination bits, leaves "to keep" destination bits intact
sta ($26),y ; write the result
;exit condition 1
ldx rnd2
bne @loop
;wait while checking for keypress
@wait lda $c000
ldx $c000
bmi @exit
;and exit condition
;exit condition 2
@rnd2 lda #0
bne @loop
@rnd1 lda #0
cmp #1
ldx rnd1
dex
bne @loop
@exit rts
@copymasks
!byte 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1
!byte 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2
!byte 4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4
!byte 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8
!byte 16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16
!byte 32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32
!byte 64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64
!byte 128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128