prog8/examples/plasma.p8
2020-08-21 17:58:43 +02:00

102 lines
2.9 KiB
Lua

%import c64lib
;/*****************************************************************************\
;** plasma test program for cc65. **
;** **
;** (w)2001 by groepaz/hitmen **
;** **
;** Cleanup and porting by Ullrich von Bassewitz. **
;** Converted to prog8 by Irmen de Jong **
;** **
;\*****************************************************************************/
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() {
c64.COLOR = 1
c64scr.print("creating charset...\n")
makechar()
ubyte block = c64.CIA2PRA
; ubyte v = c64.VMCSB
c64.CIA2PRA = (block & $FC) | (lsb(SCREEN1 >> 14) ^ $03)
repeat {
doplasma(SCREEN1)
c64.VMCSB = PAGE1
doplasma(SCREEN2)
c64.VMCSB = PAGE2
}
; restore screen (if you want)
;c64.VMCSB = v
;c64.CIA2PRA = block
;c64scr.print("done!\n")
}
; 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
ubyte @zp x
ubyte @zp y
for y in 0 to 24 {
ybuf[y] = sin8u(c1a) + sin8u(c1b)
c1a += 4
c1b += 9
}
c1A += 3
c1B -= 5
for x in 0 to 39 {
xbuf[x] = sin8u(c2a) + sin8u(c2b)
c2a += 3
c2b += 7
}
c2A += 2
c2B -= 3
for y in 0 to 24 {
for x in 0 to 39 {
@(screen) = xbuf[x] + ybuf[y]
screen++
}
}
}
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*8.w) = b
}
}
}
}