unity3d中判断鼠标是否在屏幕指定区域内

下面是unity自带的,在Scripts资源包里有拖拽代码，这个拖拽物体必须附加Rigidbody刚体组件。
DragRigidbody.js

var spring = 50.0;
var damper = 5.0;
var drag = 10.0;
var angularDrag = 5.0;
var distance = 0.2;
var attachToCenterOfMass = false;

private var springJoint : SpringJoint;

function Update ()
{
// Make sure the user pressed the mouse down
if (!Input.GetMouseButtonDown (0))
return;

var mainCamera = FindCamera();

// We need to actually hit an object
var hit : RaycastHit;
if (!Physics.Raycast(mainCamera.ScreenPointToRay(Input.mousePosition), hit, 100))
return;
// We need to hit a rigidbody that is not kinematic
if (!hit.rigidbody || hit.rigidbody.isKinematic)
return;

if (!springJoint)
{
var go = new GameObject("Rigidbody dragger");
var body : Rigidbody = go.AddComponent ("Rigidbody") as Rigidbody;
springJoint = go.AddComponent ("SpringJoint");
body.isKinematic = true;
}

springJoint.transform.position = hit.point;
if (attachToCenterOfMass)
{
var anchor = transform.TransformDirection(hit.rigidbody.centerOfMass) + hit.rigidbody.transform.position;
anchor = springJoint.transform.InverseTransformPoint(anchor);
springJoint.anchor = anchor;
}
else
{
springJoint.anchor = Vector3.zero;
}

springJoint.spring = spring;
springJoint.damper = damper;
springJoint.maxDistance = distance;
springJoint.connectedBody = hit.rigidbody;

StartCoroutine ("DragObject", hit.distance);
}

function DragObject (distance : float)
{
var oldDrag = springJoint.connectedBody.drag;
var oldAngularDrag = springJoint.connectedBody.angularDrag;
springJoint.connectedBody.drag = drag;
springJoint.connectedBody.angularDrag = angularDrag;
var mainCamera = FindCamera();
while (Input.GetMouseButton (0))
{
var ray = mainCamera.ScreenPointToRay (Input.mousePosition);
springJoint.transform.position = ray.GetPoint(distance);
yield;
}
if (springJoint.connectedBody)
{
springJoint.connectedBody.drag = oldDrag;
springJoint.connectedBody.angularDrag = oldAngularDrag;
springJoint.connectedBody = null;
}
}

function FindCamera ()
{
if (camera)
return camera;
else
return Camera.main;
}

编程回忆录已经有八年的历史，是教程团队旗下的一个在线网络培训机构，目前已录制十三个科目，涉及到互联网开发，软件开发，游戏开发（虚拟现实开发）,现在编程回忆录的Unity3D是国内唯一一家中文连载的大型视频教程。零基础开始讲解，通俗易懂 ,以实战为目地，受到众多网友的一致好评。