prog8/examples/mandelbrot-stackvm.p8

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%import c64utils
%import c64flt
~ main {
const uword width = 320 / 2
const uword height = 256 / 2
const uword xoffset = 40
const uword yoffset = 30
sub start() {
vm_gfx_clearscr(11)
vm_gfx_text(2, 1, 1, "Calculating Mandelbrot Fractal...")
for ubyte pixely in yoffset to yoffset+height-1 {
float yy = (pixely-yoffset as float)/3.6/height+0.4
for uword pixelx in xoffset to xoffset+width-1 {
float xx = (pixelx-xoffset as float)/3.0/width+0.2
float xsquared = 0.0
float ysquared = 0.0
float x = 0.0
float y = 0.0
ubyte iter = 0
while (iter<32 and xsquared+ysquared<4.0) {
y = x*y*2.0 + yy
x = xsquared - ysquared + xx
xsquared = x*x
ysquared = y*y
iter++
}
vm_gfx_pixel(pixelx, pixely, iter)
}
}
vm_gfx_text(11, 21, 1, "Finished!")
}
}