mirror of
https://github.com/irmen/prog8.git
synced 2024-12-20 20:31:51 +00:00
75 lines
2.6 KiB
Lua
75 lines
2.6 KiB
Lua
; Animate a zooming star field.
|
|
; Rather than doing complicated 3d stuff, this simply uses polar coordinates.
|
|
; Every star lies along the circle and has a radius.
|
|
; Movement is dictated by a random accelleration, which increases the speed, which increases the radius.
|
|
|
|
; TODO extend the radius to a larger maximum (0-319 or perhaps 0-511, instead of 0-255) so that we can fill the whole screen.
|
|
|
|
%import math
|
|
%import palette
|
|
%import gfx_lores
|
|
%option no_sysinit
|
|
|
|
main {
|
|
%option verafxmuls
|
|
|
|
sub start() {
|
|
const ubyte NUM_STARS = 128 ; maximum is 128.
|
|
const ubyte CIRCLE_SKIP = 256/NUM_STARS
|
|
|
|
ubyte[NUM_STARS] color
|
|
uword[NUM_STARS] radius
|
|
uword[NUM_STARS] accel
|
|
uword[NUM_STARS] speed
|
|
uword[NUM_STARS] prev_x
|
|
ubyte[NUM_STARS] prev_y
|
|
|
|
gfx_lores.graphics_mode()
|
|
|
|
; init the star positions
|
|
ubyte star
|
|
for star in 0 to NUM_STARS-1 {
|
|
color[star] = star
|
|
accel[star] = (math.rnd() & 15) | 1
|
|
radius[star] = mkword(math.rnd() & %11111000, 0)
|
|
speed[star] = 0 ; radius[star] >> 6 ; a slow buildup of movement at the start is kinda nice I think, so we start with speed zero
|
|
}
|
|
|
|
const uword angle = 0 ; if you make this a variable and increase it, the stars rotate.
|
|
|
|
repeat {
|
|
sys.waitvsync()
|
|
;;palette.set_color(0, $400)
|
|
for star in NUM_STARS-1 downto 0 {
|
|
|
|
gfx_lores.plot(prev_x[star], prev_y[star], 0)
|
|
|
|
cx16.r2L = star*CIRCLE_SKIP + msb(angle)
|
|
uword sx = (msb(math.sin8(cx16.r2L) as word * msb(radius[star])) + 128) as uword + 32
|
|
ubyte sy = (msb(math.cos8(cx16.r2L) as word * msb(radius[star])) + 120)
|
|
|
|
prev_x[star] = sx
|
|
if sy<240 {
|
|
prev_y[star] = sy
|
|
gfx_lores.plot(sx, sy, color[star])
|
|
} else
|
|
prev_y[star] = 0
|
|
|
|
if radius[star] > $fffe - speed[star] {
|
|
; reset star to center
|
|
accel[star] = (math.rnd() & 15) | 1
|
|
radius[star] = $0400 + accel[star] * 128
|
|
speed[star] = 0 ; radius[star] >> 6
|
|
color[star] = math.rnd()
|
|
} else {
|
|
; can still move more.
|
|
radius[star] += speed[star]
|
|
speed[star] += accel[star]
|
|
}
|
|
}
|
|
;; angle += $0040
|
|
;;palette.set_color(0, $000)
|
|
}
|
|
}
|
|
}
|