54 lines
1.6 KiB
JavaScript
54 lines
1.6 KiB
JavaScript
import { lerp, drawCircle, drawLine, drawDashedLine, resizeCanvas } from "./common.js"
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const points = [];
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function cubicBezier(a, b, c, d, res=0.05) {
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const eps = 0.001; // to prevent issues with float comparaison (p <= 1)
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const curve = [];
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for (let p = 0; p - 1 < eps; p += res) {
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const ab = lerp(a, b, p);
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const bc = lerp(b, c, p);
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const cd = lerp(c, d, p);
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const abc = lerp(ab, bc, p);
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const bcd = lerp(bc, cd, p);
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const abcd = lerp(abc, bcd, p);
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curve.push(abcd);
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console.log(p);
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}
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return curve;
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}
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function init() {
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const canvas = document.getElementById("canvas");
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if (canvas.getContext) {
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const ctx = canvas.getContext("2d");
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resizeCanvas(ctx); // Init canvas to full window size
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canvas.addEventListener("click", (evt) => {
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const {clientX, clientY} = evt;
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if (points.length < 4) {
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const p = {x: clientX, y: clientY};
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points.push(p);
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drawCircle(ctx, p, 1, 0xFF00FF);
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if (points.length == 4) {
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const [a, b, c, d] = points;
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drawDashedLine(ctx, a, b, 0xFF00FF);
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drawDashedLine(ctx, b, c, 0xFF00FF);
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drawDashedLine(ctx, c, d, 0xFF00FF);
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const curve = cubicBezier(a, b, c, d);
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for (let i=0; i < curve.length - 1; ++i) {
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drawLine(ctx, curve[i], curve[i+1], 0xFFFFFF);
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}
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}
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}
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});
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window.addEventListener('resize', () => resizeCanvas(ctx));
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}
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}
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init();
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