书籍名称：HTML5-Animation-with-JavaScript
书籍源码：https://github.com/lamberta/html5-animation
1.正弦函数。x位置递增，y位置用sin生成。
这段代码是不需要ball.js的。
代码如下：
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Wave 2</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>
<script src="../include/utils.js"></script>
<script>
window.onload = function () {
var canvas = document.getElementById(‘canvas‘),
context = canvas.getContext(‘2d‘),
angle = 0,
range = 50,
centerY = canvas.height / 2,
xspeed = 1,
yspeed = 0.05,
xpos = 0,
ypos = centerY;
context.lineWidth = 2;
(function drawFrame () {
window.requestAnimationFrame(drawFrame, canvas);
context.beginPath();
context.moveTo(xpos, ypos);
//Calculate the new position.
xpos += xspeed;
angle += yspeed;
ypos = centerY + Math.sin(angle) * range;
context.lineTo(xpos, ypos);
context.stroke();
}());
};
</script>
</body>
</html>
2.做环绕运动，就是求旋转角度对应在圆上的坐标，由下图可以看出x的值是半径r*cos（angle）,而y则为r*sin(angle)，由于canvas的坐标不同于传统的坐标系，大家自行与传统坐标系区别开。
椭圆运动则是某方向值偏大。
上代码：08-circle.html
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Circle</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>
<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‘),
ball = new Ball(),
angle = 0,
centerX = canvas.width / 2,
centerY = canvas.height / 2,
radius = 50,
speed = 0.05;
(function drawFrame () {
window.requestAnimationFrame(drawFrame, canvas);
context.clearRect(0, 0, canvas.width, canvas.height);
ball.x = centerX + Math.cos(angle) * radius;
ball.y = centerY + Math.sin(angle) * radius;
angle += speed;
ball.draw(context);
}());
};
</script>
</body>
</html>
09-oval.html
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Oval</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>
<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‘),
ball = new Ball(),
angle = 0,
centerX = canvas.width / 2,
centerY = canvas.height / 2,
radiusX = 150,
radiusY = 100,
speed = 0.05;
(function drawFrame () {
window.requestAnimationFrame(drawFrame, canvas);
context.clearRect(0, 0, canvas.width, canvas.height);
ball.x = centerX + Math.cos(angle) * radiusX;
ball.y = centerY + Math.sin(angle) * radiusY;
angle += speed;
ball.draw(context);
}());
};
</script>
</body>
</html>
时间： 2024-10-09 21:54:34