Fredkin Replicator (non-minified versio… by pavel

function u(t) {

c.width=1920 // clear the canvas
for(i=0;i<9;i++)
x.fillRect(400+i*100+S(t)*300,400,50,200) // draw 50x200 rects

} // 122/140

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    u(t) is called 60 times per second.
    t: Elapsed time in seconds.
    S: Shorthand for Math.sin.
    C: Shorthand for Math.cos.
    T: Shorthand for Math.tan.
    R: Function that generates rgba-strings, usage ex.: R(255, 255, 255, 0.5)
    c: A 1920x1080 canvas.
    x: A 2D context for that canvas.

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pavel

remix of d/11391 by u/pavel

function u(t) {

for(a=t?b:{8256:1},i=frame%9==1&t<9.5&&(c.width|=b={},2e5);i--;x.fillRect(i&1017,i>>7,8,a[q]*8))k=i%8+5,b[q=i>>3]^=a[q+k%3*128+k/3%3-129|0]

Dec 15 2018 2:32 AM UTC

}// 139/140

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Fredkin Replicator (non-minified version)

Show more comments…
u/pavel

Using div/mod to store 128x128 pixel coordinates in a. 8256=128*64+64 is the middle pixel.
u/pavel

Using frame%9==1 to update the automata once every nine frames. Frames are 1 indexed.
u/pavel

i encodes three variables: lowest 3 bits is neighbor cell 'index', middle 7 is x, and upper 7 is y.
u/pavel

To get neighbor cells I do the div/mod trick on the 'index' but need to exclude (0,0) which has index 4. So I map cell index to i%8+5 which %9 is [5,6,7,8,0,1,2,3]
u/pavel

A cell is 'on' iff the parity of its 'on' neighbors is odd which is the same as the xor of neighbor states
u/pavel

I cheat a little. Y=i>>10 so my rect should use (i>>10)*8 but to save chars I use i>>7. The cells are slightly off-place vertically but its hard to notice.
u/pavel

i&1017 is a mistake, oops, should be i&1016, causes tiny visual glitch. 1016=0b1111111000 which is X*8
u/pavel

#uncompressed


      u(t) is called 60 times per second.
      t: elapsed time in seconds.
      c: A 1920x1080 canvas.
      x: A 2D context for that canvas.
      S: Math.sin
      C: Math.cos
      T: Math.tan
      R: Generates rgba-strings, ex.: R(255, 255, 255, 0.5)

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