Created
November 13, 2018 12:02
-
-
Save ds604/9c57fd37aa15700e9b7963880d7e8f60 to your computer and use it in GitHub Desktop.
Bouncing Ball
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
interface Numeric<T> { | |
plus(other: T): T | |
times(scalar: number): T | |
} | |
function runSimulation<T extends Numeric<T>>( | |
y0: T, | |
f: (t: number, y: T) => T, | |
applyConstraints: (y: T) => T, | |
iterationsPerFrame: number, | |
render: (y: T) => void | |
) { | |
const frameTime = 1 / 60.0 | |
const h = frameTime / iterationsPerFrame | |
function simulationStep(yi: T, ti: number) { | |
render(yi) | |
requestAnimationFrame(function () { | |
for (let i = 0; i < iterationsPerFrame; i++) { | |
yi = yi.plus(f(ti, yi).times(h)) | |
yi = applyConstraints(yi) | |
ti = ti + h | |
} | |
simulationStep(yi, ti) | |
}) | |
} | |
simulationStep(y0, 0.0) | |
} | |
const canvas = document.createElement("canvas") | |
canvas.width = 400; | |
canvas.height = 400; | |
const ctx = canvas.getContext("2d")!; | |
document.body.appendChild(canvas); | |
ctx.fillStyle = "rgba(0, 0, 0, 0, 1)" | |
ctx.fillRect(0, 0, 400, 400); | |
const g = -9.8; // m / s^2 | |
const r = 0.2; // m | |
class Ball implements Numeric<Ball> { | |
constructor(readonly x: number, readonly v: number) { } | |
plus(other: Ball) { return new Ball(this.x + other.x, this.v + other.v) } | |
times(scalar: number) { return new Ball(this.x * scalar, this.v * scalar) } | |
} | |
function f(t: number, y: Ball) { | |
const { x, v } = y | |
return new Ball(v, g) | |
} | |
function applyConstraints(y: Ball): Ball { | |
const { x, v } = y | |
if (x <= 0 && v < 0) { | |
return new Ball(x, -v) | |
} | |
return y | |
} | |
const y0 = new Ball( | |
/* x */ 0.8, | |
/* v */ 0 | |
) | |
function render(y: Ball) { | |
ctx.clearRect(0, 0, 400, 400) | |
ctx.fillStyle = '#EB5757' | |
ctx.beginPath() | |
ctx.ellipse(200, 400 - ((y.x + r) * 300), r * 300, r * 300, 0, 0, 2 * Math.PI) | |
ctx.fill() | |
} | |
runSimulation(y0, f, applyConstraints, 30, render) |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
canvas { | |
border: 1px solid black; | |
} |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment