prog8/examples/c64/plasma.p8

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%import syslib
%import textio
%import math
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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.
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; See https://github.com/cc65/cc65/tree/master/samples/cbm/plasma.c
;
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; Optimized and 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.clear_screen()
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txt.print("creating charset...\n\nwhile running, press key to stop.\n\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)
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uword frames = 0
cbm.SETTIM(0,0,0)
while cbm.GETIN()==0 {
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doplasma(SCREEN1)
c64.VMCSB = PAGE1
doplasma(SCREEN2)
c64.VMCSB = PAGE2
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frames += 2
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}
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uword jiffies = cbm.RDTIM16()
; restore screen and displays stats
c64.VMCSB = v
c64.CIA2PRA = block
txt.print("time in jiffies: ")
txt.print_uw(jiffies)
txt.print("\nframes: ")
txt.print_uw(frames)
uword fps = (frames*60)/jiffies
txt.print("\nfps: ")
txt.print_uw(fps)
txt.print("\ndone!\n")
repeat {
}
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}
; several variables outside of doplasma to make them retain their value
ubyte c1A
ubyte c1B
ubyte c2A
ubyte c2B
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sub doplasma(uword @zp screen) {
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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 0 to 24 {
ybuf[y] = math.sin8u(c1a) + math.sin8u(c1b)
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c1a += 4
c1b += 9
}
c1A += 3
c1B -= 5
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for x in 0 to 39 {
xbuf[x] = math.sin8u(c2a) + math.sin8u(c2b)
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c2a += 3
c2b += 7
}
c2A += 2
c2B -= 3
for y in 0 to 24 {
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ubyte @zp @shared yvalue = ybuf[y]
for x in 0 to 39 {
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; @(screen+x) = xbuf[x] + yvalue
; max optimized asm is this: (achieving ~21 fps on the C64):
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%asm {{
lda p8_yvalue
ldy p8_x
clc
adc p8_xbuf,y
sta (p8_screen),y
}}
}
screen += 40
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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 {
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ubyte @zp s = math.sin8u(c) ; chance
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ubyte i
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; for all the pixels in the 8x8 character grid, determine (with a rnd chance) if they should be on or off
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for i in 0 to 7 {
ubyte b=0
ubyte @zp ii
for ii in 0 to 7 {
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if math.rnd() > s
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b |= bittab[ii]
}
@(CHARSET + i + c*$0008) = b
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}
}
}
}