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f0a01ed Dec 23, 2011
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<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Throwing</title>
<link rel="stylesheet" href="../include/style.css">
</head>
<body>
<header>
Example from <a href="http://amzn.com/1430236655?tag=html5anim-20"><em>Foundation HTML5 Animation with JavaScript</em></a>
</header>
<canvas id="canvas" width="400" height="400"></canvas>
<aside>Press, drag, and throw circle with mouse.</aside>
<script src="../include/utils.js"></script>
<script src="./classes/ball.js"></script>
<script>
window.onload = function () {
var canvas = document.getElementById('canvas'),
context = canvas.getContext('2d'),
mouse = utils.captureMouse(canvas),
ball = new Ball(),
vx = Math.random() * 10 - 5,
vy = -10,
bounce = -0.7,
gravity = 0.2,
isMouseDown = false,
oldX, oldY;
ball.x = canvas.width / 2;
ball.y = canvas.height / 2;
canvas.addEventListener('mousedown', function () {
if (utils.containsPoint(ball.getBounds(), mouse.x, mouse.y)) {
isMouseDown = true;
oldX = ball.x;
oldY = ball.y;
canvas.addEventListener('mouseup', onMouseUp, false);
canvas.addEventListener('mousemove', onMouseMove, false);
}
}, false);
function onMouseUp () {
isMouseDown = false;
canvas.removeEventListener('mouseup', onMouseUp, false);
canvas.removeEventListener('mousemove', onMouseMove, false);
}
function onMouseMove (event) {
ball.x = mouse.x;
ball.y = mouse.y;
}
function trackVelocity () {
vx = ball.x - oldX;
vy = ball.y - oldY;
oldX = ball.x;
oldY = ball.y;
}
function checkBoundaries () {
var left = 0,
right = canvas.width,
top = 0,
bottom = canvas.height;
vy += gravity;
ball.x += vx;
ball.y += vy;
//boundary detect and bounce
if (ball.x + ball.radius > right) {
ball.x = right - ball.radius;
vx *= bounce;
} else if (ball.x - ball.radius < left) {
ball.x = left + ball.radius;
vx *= bounce;
}
if (ball.y + ball.radius > bottom) {
ball.y = bottom - ball.radius;
vy *= bounce;
} else if (ball.y - ball.radius < top) {
ball.y = top + ball.radius;
vy *= bounce;
}
}
(function drawFrame () {
window.requestAnimationFrame(drawFrame, canvas);
context.clearRect(0, 0, canvas.width, canvas.height);
if (isMouseDown) {
trackVelocity();
} else {
checkBoundaries();
}
ball.draw(context);
}());
};
</script>
</body>
</html>