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c06.html
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c06.html
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<!DOCTYPE html>
<html>
<head>
<title>Example</title>
<style>
body {
background: #dddddd;
}
#canvas {
background: #ffffff;
border: thin inset #aaaaaa;
}
</style>
</head>
<body>
<canvas id='canvas' width="800" height="600">
Canvas not supported
</canvas>
<script>
var canvas = document.getElementById("canvas");
var context = canvas.getContext("2d");
function windowToCanvas(x, y) {
var bbox = canvas.getBoundingClientRect();
return { x : x - bbox.left, y : y - bbox.top }
}
function Ball() {
this.x = 0;
this.y = 0;
this.radius = 10;
this.color = "red";
this.angle = 0;
}
Ball.prototype = {
draw : function() {
context.save();
context.beginPath();
context.translate(this.x, this.y);
context.rotate(this.angle);
context.arc(0, 0, this.radius, 0, Math.PI * 2);
context.fillRect(-30, -5, 30, 10);
context.fillStyle = this.color;
context.fill();
context.restore();
}
}
var ball = new Ball();
var vx = 0;
var vy = 0;
var angle = -45;
var speed = 5;
ball.x = 100;
ball.y = 500;
//ball.angle = 45 * Math.PI / 180;
canvas.onmousemove = function(e) {
var loc = windowToCanvas(e.clientX, e.clientY);
var dx = loc.x - ball.x;
var dy = loc.y - ball.y;
angle = Math.atan2(dy, dx);
vx = Math.cos(angle) * speed;
vy = Math.sin(angle) * speed;
};
requestAnimationFrame(loop);
function loop() {
context.clearRect(0, 0, canvas.width, canvas.height);
ball.angle = Math.atan2(vy, vx);
ball.x += vx;
ball.y += vy;
render();
requestAnimationFrame(loop);
}
function render() {
ball.draw();
}
</script>
</body>
</html>