84 lines
2.6 KiB
TypeScript
84 lines
2.6 KiB
TypeScript
import Vec2d from "./vec.js";
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import { drawCircle, resizeCanvas } from "./common.js";
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// state
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let target: Vec2d | undefined = undefined;
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let pos = new Vec2d(200, 200);
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let velocity = new Vec2d(500, 500);
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let pause = false;
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let mode: "follow" | "bounce" = "bounce";
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let start: number | undefined = undefined;
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function update(ctx: CanvasRenderingContext2D, timestamp: number) {
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switch (mode) {
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case "bounce":
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updateBounce(ctx, timestamp);
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break;
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case "follow":
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updateFollow(ctx);
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break;
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default:
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throw new Error(`Unknown mode: ${mode}`);
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}
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if (!pause) window.requestAnimationFrame(t => update(ctx, t));
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}
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function updateFollow(ctx: CanvasRenderingContext2D) {
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if (target) pos = pos.lerp(target, 0.01);
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ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
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drawCircle(ctx, pos, 100, 0xFF00FF);
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}
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function updateBounce(ctx: CanvasRenderingContext2D, timestamp: number) {
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if (!start) start = timestamp;
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const dt = timestamp - start;
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// P_t+1 = P_t + V * t
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const newPos = pos.add(velocity.scale(0.001*dt));
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if (newPos.x > ctx.canvas.width - 100) { velocity.x *= -1; newPos.x = ctx.canvas.width - 100; }
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if (newPos.y > ctx.canvas.height - 100) { velocity.y *= -1; newPos.y = ctx.canvas.height - 100; }
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if (newPos.x < 100) { velocity.x *= -1; newPos.x = 100; }
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if (newPos.y < 100) { velocity.y *= -1; newPos.y = 100; }
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//console.log(velocity);
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pos = newPos;
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ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
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drawCircle(ctx, pos, 100, 0xFF00FF);
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start = timestamp;
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}
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function init() {
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const canvas = document.getElementById("canvas") as HTMLCanvasElement | null;
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if (!canvas) throw new Error("unable to get canvas HTML element");
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const ctx = canvas.getContext("2d") as CanvasRenderingContext2D | null;
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if (!ctx) throw new Error("unable to get canvas 2D context");
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ctx.canvas.width = window.innerWidth;
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ctx.canvas.height = window.innerHeight;
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canvas.onmousemove = (evt) => {
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const {clientX, clientY} = evt;
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target = new Vec2d(clientX, clientY);
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}
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canvas.onclick = () => {
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if (pause) {
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window.requestAnimationFrame(t => update(ctx, t));
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}
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pause = !pause;
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}
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window.onkeydown = (evt) => {
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console.log("key down", evt);
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if (mode === "follow") mode = "bounce";
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else mode = "follow"
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console.log("mode", mode);
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}
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window.addEventListener('resize', () => resizeCanvas(ctx));
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window.requestAnimationFrame(t => update(ctx, t));
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}
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init();
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