摄像机碰到后面物体缩进视口

var camera1:Camera;

var mousescrollwheel_y:float;                             //摄像机Y轴的点
var mousescrollwheel_z:float;                            //摄像机z轴的点
var sensitivityW:float=5;                                     //滚轮敏捷

var pnearviewZ:float=-1;                                      //离近的z点距离
var pnearviewY:float=-1;                                      //离近的Y点距离
var meetdistance:float=3;                                    //光线的距离

var nearview_y:float=-1;                                        //最小Y
var farview_y:float=-5;                                           //最大Y
var nearview_z:float=-1;                                        //最小Z
var farview_z:float=-10;                                       //最大Z
function Start ()
{
    mousescrollwheel_z=camera1.transform.localPosition.z;
    mousescrollwheel_y=camera1.transform.localPosition.y;
}

function Update () {

    mousescrollwheel_z += Input.GetAxis("Mouse ScrollWheel")*sensitivityW;
    mousescrollwheel_y += Input.GetAxis("Mouse ScrollWheel")*sensitivityW;
    if(mousescrollwheel_z>nearview_z){mousescrollwheel_z=nearview_z;}
    else if(mousescrollwheel_z<farview_z){mousescrollwheel_z=farview_z;}
    if(mousescrollwheel_y>nearview_y){mousescrollwheel_y=nearview_y;}
    else if(mousescrollwheel_y<farview_y){mousescrollwheel_y=farview_y;}
    camera1.transform.localPosition.z=mousescrollwheel_z;
    camera1.transform.localPosition.y=-mousescrollwheel_y;
    var fwd = transform.TransformDirection (-(Vector3.forward));
    var hit:RaycastHit;
    if (Physics.Raycast (transform.position, fwd, hit,meetdistance)) {
        if(hit.transform.tag=="wall"){
            camera1.transform.localPosition.z=pnearviewZ;
            camera1.transform.localPosition.y=-pnearviewY;
        }
    }

}