prog8/examples/plasma.p8

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%target c64
%import syslib
%import textio
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; converted from plasma test program for cc65.
; which is (w)2001 by groepaz/hitmen
;
; Cleanup and porting to C by Ullrich von Bassewitz.
; Converted to prog8 by Irmen de Jong.
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main {
const uword SCREEN1 = $E000
const uword SCREEN2 = $E400
const uword CHARSET = $E800
const ubyte PAGE1 = ((SCREEN1 >> 6) & $F0) | ((CHARSET >> 10) & $0E)
const ubyte PAGE2 = ((SCREEN2 >> 6) & $F0) | ((CHARSET >> 10) & $0E)
sub start() {
txt.color(1)
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txt.print("creating charset...\n")
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makechar()
ubyte block = c64.CIA2PRA
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; ubyte v = c64.VMCSB
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c64.CIA2PRA = (block & $FC) | (lsb(SCREEN1 >> 14) ^ $03)
repeat {
doplasma(SCREEN1)
c64.VMCSB = PAGE1
doplasma(SCREEN2)
c64.VMCSB = PAGE2
}
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; restore screen (if you want)
;c64.VMCSB = v
;c64.CIA2PRA = block
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;txt.print("done!\n")
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}
; several variables outside of doplasma to make them retain their value
ubyte c1A
ubyte c1B
ubyte c2A
ubyte c2B
sub doplasma(uword screen) {
ubyte[40] xbuf
ubyte[25] ybuf
ubyte c1a = c1A
ubyte c1b = c1B
ubyte c2a = c2A
ubyte c2b = c2B
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ubyte @zp x
ubyte @zp y
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for y in 24 downto 0 {
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ybuf[y] = sin8u(c1a) + sin8u(c1b)
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c1a += 4
c1b += 9
}
c1A += 3
c1B -= 5
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for x in 39 downto 0 {
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xbuf[x] = sin8u(c2a) + sin8u(c2b)
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c2a += 3
c2b += 7
}
c2A += 2
c2B -= 3
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for y in 24 downto 0 {
for x in 39 downto 0 {
; using a temp var here to enable expression optimization that can't be done on a 'problematic' ROM/RAM memory location
ubyte cc = xbuf[x] + ybuf[y]
@(screen) = cc
; this is the fastest way to do this inner part:
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; %asm {{
; ldy i
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; lda xbuf,y
; ldy ii
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; clc
; adc ybuf,y
; ldy #0
; sta (screen),y
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; }}
screen++
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}
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}
}
sub makechar() {
ubyte[8] bittab = [ $01, $02, $04, $08, $10, $20, $40, $80 ]
ubyte c
for c in 0 to 255 {
ubyte @zp s = sin8u(c)
ubyte i
for i in 0 to 7 {
ubyte b=0
ubyte @zp ii
for ii in 0 to 7 {
; use 16 bit rng for a bit more randomness instead of the 8-bit rng
if lsb(rndw()) > s {
b |= bittab[ii]
}
}
@(CHARSET + i + c*$0008) = b
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}
}
}
}