由网友(微风吹过的声音)分享简介：我正与此函数移动的物体围绕在一个完美的圆圈的中心点，我试图修改它以移动为椭圆形的1/2高，因为它是宽？I am working with this function that moves an object around a center point in a perfect circle and am trying...

我正与此函数移动的物体围绕在一个完美的圆圈的中心点，我试图修改它以移动为椭圆形的1/2高，因为它是宽？

I am working with this function that moves an object around a center point in a perfect circle and am trying to modify it to move it in an oval shape that is 1/2 as high as it is wide?

基本上，我有一个设定速度

Basically, I have a set speed

var myVelocity:Number = 0.25;

然后，我计算我的基于速度正弦和余弦

then I calculate my Sine and Cosine based on the speed

var myCos:Number = Math.cos(myVelocity);
var mySin:Number = Math.sin(myVelocity);

那么我想从一个固定的中心点沿每个轴的物体的距离和

then I figure the distance of the the object from a fixed center points along each axis and

var x1:Number = myBall.x - centerX;
var y1:Number = myBall.y - centerY;
var x2:Number = myCos * x1 - mySin * y1;
var y2:Number = myCos * y1 + mySin * x1;
myBall.x = centerX + x2;
myBall.y = centerY + y2;

我有另一个函数，数字基于myBall.x =的centerX + COS（角度）x和y *半径;这是很容易修改半径变成椭圆，但有一个简单的方法，以mod上述之一，成为一个椭圆？我想这样做是与code更有效，更减少了数学函数的调用次数

I have another function that figures x and y based upon myBall.x = centerX + cos(angle) * radius; that is easy enough to modify the radius to become an ellipse, but is there an easy way to mod the one above to become an ellipse? I want to do this to be more efficient with the code and reduce the number of math function calls

推荐答案

这个问题几乎是逐字什么基思·彼得斯覆盖基金会的ActionScript 3.0：使事情移动

This question is nearly verbatim to what Keith Peters covers in Foundation Actionscript 3.0: Making Things Move!

我从书上刮起了快速的片断给你。

I've whipped up a quick snippet for you from the book.

import flash.display.Shape;
import flash.events.Event;

var box:Shape = new Shape();
box.graphics.beginFill(0xFF0000);
box.graphics.drawRect(0, 0, 50, 50);
box.graphics.endFill();
addChild(box);
var angle:Number = 0;
var centerX:Number = stage.stageWidth/2 - (box.width/2);
var centerY:Number = stage.stageHeight/2 - (box.height/2)
var radiusX:Number = 200;
var radiusY:Number = 100;
var speed:Number = .1;
stage.addEventListener(Event.ENTER_FRAME, loop, false, 0, true);

function loop(evt:Event):void
{
    box.x = centerX + Math.sin(angle) * radiusX;
    box.y = centerY + Math.cos(angle) * radiusY;
    angle += speed;
}

结果： http://www.swfupload.com/view/155573.htm