坐标旋转

坐标旋转： x1 = Math.cos(angle) * x - Math.sin(angle) * y; y1 = Math.cos(angle) * y + Math.sin(angle) * x;

反坐标旋转： x1 = Math.cos(angle) * x + Math.sin(angle) * y; y1 = Math.cos(angle) * y - Math.sin(angle) * x;

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private function onEnterFrame(event:Event):void {

// 普通的运动代码
ball.vy += gravity;
ball.x += ball.vx;

ball.y += ball.vy;

// 获得角度及正余弦值
var angle:Number = line.rotation * Math.PI / 180;
var cos:Number = Math.cos(angle);
var sin:Number = Math.sin(angle);

// 获得 ball 与 line 的相对位置
var x1:Number = ball.x - line.x;
var y1:Number = ball.y - line.y;

// 旋转坐标
var y2:Number = cos * y1 - sin * x1;

// 实现反弹
if(y2 > -ball.height / 2) {

// 旋转坐标
var x2:Number = cos * x1 + sin * y1;

// 旋转速度向量
var vx1:Number = cos * ball.vx + sin * ball.vy;
var vy1:Number = cos * ball.vy - sin * ball.vx;
y2 = -ball.height / 2; vy1 *= bounce;

// 将一切旋转回去
x1 = cos * x2 - sin * y2;
y1 = cos * y2 + sin * x2;
ball.vx = cos * vx1 - sin * vy1;
ball.vy = cos * vy1 + sin * vx1;
ball.x = line.x + x1;
ball.y = line.y + y1;
} }