从球形绳的制作学习简单三维(下)

//xoff,yoff,zoff用来确定我们观察者所处的位置.
xoff=0;
yoff=0;
zoff=0;
d=1000;
centerX=275;
centerY=200;
ang=0;
function project()
{
if((this.z-zoff)<40)
{
this._visible=false;
}
else
{
this._visible=true;
var zfactor=d/(this.z-zoff);
this._x=(this.x-xoff)*zfactor+centerX;//在上一个效果中公式中少了一个xoff,因为现在的球位置都是相对于观察者的.
this._y=(this.y-yoff)*zfactor+centerY;

this._xscale=100*zfactor;
this._yscale=100*zfactor;

this.swapDepths(Math.floor(100000-(this.z-zoff)));//让近的球摆在上面.
}
}
//接下来用于生成小球....
for(var i=0;i<40;i++)
{
var nm="sphere"+i;
_root.attachMovie("sphere",nm,i);

_root[nm].x=Math.cos(ang)*200;
ang+=0.2;
_root[nm].y=100+Math.cos(i/3)*100;

_root[nm].z=(i*50)+d;
_root[nm].project=project;

_root[nm].onEnterFrame=project;
}
//建一个侦听器,侦听鼠标的活动.
mouseListener=new Object();
mouseListener.onMouseWheel=function(diff)
{
zoff+=(diff*50)
}
mouseListener.onMouseMove=function()
{
xoff=_xmouse-centerX;
yoff=_ymouse-centerY;
}
Mouse.addListener(mouseListener);