Dreamelt - Dreamcast 128 bytes
This started as a last minute (~4 days before deadline) filler
to participate in the Byte-athlon compo but ended up being
something of its own.
First steps was to port my ArchiSmall
Acorn
Archimedes intro just to see how the code ended up on the
SH4, it was then
repurposed as a filler.
Algorithm is still the integer circle algorithm (32 bit range
with a downscale pass) and show some kind of drifting Apollonian
net that dissolve into the background.
Original idea was to do the same thing as ArchiSmall but
"modernized" (better resolution etc.), after some prototypes i
ended up using some sort of persistence
on the net structure (by adding up colors + having a background
subtract pass just after) but i failed to downsize it as it
required saturation
arithmetic, i ended up with a dissolving background / net as a
"happy accident" (just kept the background subtract pass), it
looked cool so i fiddled with parameters until i got something
worthwhile.
No background clear to save bytes, it shows whatever the BIOS
show before running the binary (Sega copyright bitmap in this
case), this ended up fine !
There is perhaps some nice ideas to do later through
manipulation of the BIOS bitmap data. (which reside in RAM; same
for the Dreamcast logo animation although i don't yet know where it
is stored and the format)
p5js sources (note : without bitmap)
function setup() {
createCanvas(640, 480)
background(0)
}
let x = 1 << 31
let y = 1 << 31
let cr = 1
let cg = 2
let cb = 3
function draw() {
let f = frameCount
loadPixels()
for (let l = 0; l < 4e4; l += 1) {
x -= y >> 2
y += x
x -= y >> 2
x += (frameCount << 19)
let px = x >>> 23
let py = (y >> 23) * 85 >> 7
let index = (((height >> 1) * width) + 64
+ px + py * width) * 4
pixels[index + 0] = 0
pixels[index + 1] = 0
pixels[index + 2] = 0
}
for (let i = 0; i < 640 * 480 * 4; i += 4) {
if ((pixels[i + 0] - cr) < 0) pixels[i + 0] =
255
pixels[i + 0] -= cr
if ((pixels[i + 1] - cg) < 0) pixels[i + 1] =
255
pixels[i + 1] -= cg
if ((pixels[i + 2] - cb) < 0) pixels[i + 2] =
255
pixels[i + 2] -= cb
}
updatePixels()
}
dc sources
mov #0x80,r2
shll16 r2
shll8 r2
mov r2,r3
l:
mov.l VIDEO_BASE,r0
mov.l OFFSET,r1
add r1,r0
mov r0,r1
shlr16 r1
i:
mov r3,r4
shar r4
shar r4
sub r4,r2
add r2,r3
mov r3,r4
shar r4
shar r4
sub r4,r2
mov r9,r8
mov #20,r7
shld r7,r8
add r8,r2 ! x += (f
<< 19)
mov r2,r6
mov #-23,r7
shld r7,r6
mov r3,r5
shad r7,r5
mov #85,r7
mul.l r5,r7
sts MACL,r7
mov #-7,r8
shad r8,r7
mov #40,r8
shll2 r8
shll2 r8
mul.l r7,r8
sts macl,r8
add r8,r6
shll2 r6
mov.l r12,@(r0,r6)
dt r1
bf i
mov.l C,r11
mov.l VIDEO_BASE,r0
mov.l SS,r10
s:
mov.l @(r0,r10),r7
add r11,r7
mov.l r7,@(r0,r10)
add #-3,r10
dt r10
bf s
nop
bra l
add #1,r9
.align 2
VIDEO_BASE: .long 0xa5200000
OFFSET: .long 0x96100
C: .long 0x00030201
F: .long 0xffffff
SS: .long 0x12C000
back to top
