71 lines
1.3 KiB
JavaScript
71 lines
1.3 KiB
JavaScript
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/*
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Duration: 52 seconds.0:52
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Hilbert curve at its sixth iteration
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Alphabet : A, B
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Constants : F + −
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Axiom : A
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Production rules:
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*/
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console.clear();
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const rules = {
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"A": "+BF-AFA-FB+",
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"B": "-AF+BFB+FA-",
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};
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let steps = 5;
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let s = "A";
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for(let i=0;i<steps;i++) {
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let ns = "";
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for(let c of s) {
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ns += rules[c] || c;
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}
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s = ns;
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}
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let [x,y] = [0,0];
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const m = 2**(-steps);
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let dir = [m,0];
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let d = 'M 0 0 ';
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const width = 1.5 * 2**-(steps+1);
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const dots = [];
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for(let c of s) {
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const [dx,dy] = dir;
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switch(c) {
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case '+':
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dir = [-dy,dx];
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break;
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case '-':
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dir = [dy,-dx];
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break;
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case 'F':
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x += dx;
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y += dy;
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d += `l ${dx} ${dy}`;
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}
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}
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const length = 2**steps - 1;
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document.getElementById('curve').setAttribute('stroke-width',width);
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document.getElementById('curve').setAttribute('d',d);
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document.getElementById('dots').setAttribute('stroke-width',width*0.4);
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document.getElementById('dots').setAttribute('d',d);
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document.getElementById('dots').setAttribute('stroke-dasharray',`0.0000001 ${2*m}`);
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function easeInOutSine(x) {
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return -(Math.cos(Math.PI * x) - 1) / 2;
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}
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function frame() {
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const period = 1000;
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const t = (new Date()-0)/period % 1000;
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document.getElementById('dots').setAttribute('stroke-dashoffset',easeInOutSine(t)*m);
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requestAnimationFrame(frame);
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}
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frame();
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