test-canvas/bezier-1.js
2024-09-26 22:46:28 +02:00

75 lines
2.2 KiB
JavaScript

import { lerp, drawCircle, drawLine, drawDashedLine, resizeCanvas } from "./common.js"
let ctx = undefined;
let points = [];
function update(time) {
ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
const p = (Math.sin(0.001 * time) + 1.0) * 0.5;
if (points.length == 2) {
const [start, end] = points;
drawCircle(ctx, lerp(start, end, p), 1, 0xFF0000);
} else if (points.length === 3) {
const [a, b, c] = points;
const ab = lerp(a, b, p);
const bc = lerp(b, c, p);
const abc = lerp(ab, bc, p);
drawDashedLine(ctx, ab, bc, 0xFF0000);
drawCircle(ctx, ab, 1, 0xFF0000);
drawCircle(ctx, bc, 1, 0xFF0000);
drawCircle(ctx, abc, 1, 0xFFFFFF);
} else if (points.length === 4) {
const [a, b, c, d] = points;
const ab = lerp(a, b, p);
const bc = lerp(b, c, p);
const cd = lerp(c, d, p);
const abc = lerp(ab, bc, p);
const bcd = lerp(bc, cd, p);
const abcd = lerp(abc, bcd, p);
drawDashedLine(ctx, ab, bc, 0xFF0000);
drawDashedLine(ctx, bc, cd, 0xFF0000);
drawDashedLine(ctx, abc, bcd, 0xFFFF00);
drawCircle(ctx, ab, 1, 0xFF0000);
drawCircle(ctx, bc, 1, 0xFF0000);
drawCircle(ctx, cd, 1, 0xFF0000);
drawCircle(ctx, abc, 1, 0xFFFF00);
drawCircle(ctx, bcd, 1, 0xFFFF00);
drawCircle(ctx, abcd, 1, 0xFFFFFF);
}
for (let i = 0; i < points.length - 1; ++i) {
const current = points[i];
const next = points[i+1];
drawLine(ctx, current, next, 0xFF00FF);
}
for (const point of points) {
drawCircle(ctx, point, 1, 0xFF00FF);
}
window.requestAnimationFrame(update);
}
function init() {
const canvas = document.getElementById("canvas");
if (canvas.getContext) {
ctx = canvas.getContext("2d");
resizeCanvas(ctx); // Init canvas to full window size
canvas.addEventListener("click", (evt) => {
const {clientX, clientY} = evt;
if (points.length < 4) {
points.push({x: clientX, y: clientY});
}
});
window.addEventListener('resize', () => resizeCanvas(ctx));
window.requestAnimationFrame(update)
}
}
init();