HTML and CSS Reference
In-Depth Information
Now, how about adding some gravity so the ball looks like it's actually hanging off the end of the mouse? Just add a
gravity
variable and add that to the
vy
for each frame. The following code (
09-spring-5.html
) uses the line drawing and gravity additions:
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Spring 5</title>
<link rel="stylesheet" href="style.css">
</head>
<body>
<canvas id="canvas" width="400" height="400"></canvas>
<script src="utils.js"></script>
<script src="ball.js"></script>
<script>
window.onload = function () {
var canvas = document.getElementById('canvas'),
context = canvas.getContext('2d'),
mouse = utils.captureMouse(canvas),
ball = new Ball(),
spring = 0.03,
friction = 0.9,
gravity = 2,
vx = 0,
vy = 0;
(function drawFrame () {
window.requestAnimationFrame(drawFrame, canvas);
context.clearRect(0, 0, canvas.width, canvas.height);
var dx = mouse.x - ball.x,
dy = mouse.y - ball.y,
ax = dx * spring,
ay = dy * spring;
vx += ax;
vy += ay;
vy += gravity;
vx *= friction;
vy *= friction;
ball.x += vx;
ball.y += vy;
context.beginPath();
context.moveTo(ball.x, ball.y);
context.lineTo(mouse.x, mouse.y);
context.stroke();
ball.draw(context);
}());
};
</script>
</body>
</html>
