Physics-game/simple_collision.html at master · mikeherring/Physics-game · GitHub

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<!doctype html>
<html>
<head>
<title>HTML5 Physics Test</title>
</head>
<body onload="init()">
    <table>
        <tr valign="top">
            <td>
	            <canvas id="myCanvas" width="500" height="300" style="border:1px solid black;">
	            </canvas>
	            <br>
	            <button onclick="go();">Go</button>
	            <button onclick="stop();">Stop</butto>
            </td>
            <td>
                <a href="index.html">Home</a>
	            <h1>Simple Collisions</h1>
                <p>New Features</p>
                <ul>
                    <li>n number of independent agents</li>
                    <li>Linear collision detection and resolution</li>
                </ul>
            </td>
        </tr>
    </table>

	<script type="text/javascript">

		var canvas = null;
		var context = null;
		var balls = [];
		var looper = null;

		function ball(x,y,r,m,vx,vy)
		{
			this.x = x;
			this.y = y;
			this.r = r;
			this.m = m;
			this.vx = vx;
			this.vy = vy;
			this.x0 = 0;
			this.y0 = 0;
			this.reset = reset;
			function reset()
			{
				this.x = this.x0;
				this.y = this.y0;
			}
			this.move = move;
			function move()
			{
				this.x0 = this.x;
				this.y0 = this.y;
				this.x += this.vx;
				this.y += this.vy;
			}
		}

		function init()
		{
			canvas = document.getElementById("myCanvas");
			context = canvas.getContext("2d");

			balls[0] = new ball(50, 50, 10, 1, 5, 0);
			balls[1] = new ball(200, 50, 10, 1, 0, 0);
			balls[2] = new ball(250, 50, 10, 1, -5, 0);
			balls[3] = new ball(300, 50, 10, 1, 0, 0);
			balls[4] = new ball(400, 50, 10, 1, 10, 0);

			draw();
			go();
		}

		function go()
		{
			looper = setInterval(animate, 30);
		}
		function stop()
		{
			clearInterval(looper);
		}

		function animate()
		{
			clear();
			update();
			resolveCollisions();
			draw();
		}

		function clear()
		{
			context.clearRect(0, 0, canvas.width, canvas.height);
		}

		function resolveCollisions()
		{
			for (var i = 0; i < balls.length; i++)
			{
				ballA = balls[i];
				for (var j = i+1; j < balls.length; j++)
				{
					ballB = balls[j];
					if (Math.abs(ballB.x - ballA.x) < ballB.r + ballA.r)
					{
						// collision!
						ballA.reset();
						ballB.reset();

						var tmp = ballB.vx;
						ballB.vx = ballA.vx;
						ballA.vx = tmp;
					}
				}
			}

			for(var i = 0; i < balls.length; i++)
			{
				b = balls[i];
				if (b.x < b.r)
				{
					b.vx *= -1;
				}
				if (b.x > canvas.width - b.r)
				{
					b.vx *= -1;
				}
			}
		}

		function update()
		{
			for (var i = 0; i < balls.length; i++)
			{
				var b = balls[i];
				b.move();
			}
		}

		function draw()
		{
			context.beginPath();
			for (var i = 0; i < balls.length; i++)
			{
				var b = balls[i];
				context.arc(b.x, b.y, b.r, 0, 2*Math.PI);
			}
			context.closePath();
			context.fill();
		}

	</script>
</body>
</html>