【Unity】Viewportを利用したWorldPoint(position)の画面外のposition

public static Camera mainCamera;

public static float startWorldPointX;
public static float endWorldPointX;
public static float startWorldPointY;
public static float endWorldPointY;


void Start () {

    mainCamera = GameObject .FindGameObjectWithTag("MainCamera" ).GetComponent <Camera> ();

    // Viewポートの一番左のX座標
    GM.startWorldPointX = GM.mainCamera.ViewportToWorldPoint(new Vector3 (0.0f, 1.0f, GM .mainCamera. nearClipPlane)).x;
    // Viewポートの一番右のX座標
    GM.endWorldPointX = GM.mainCamera.ViewportToWorldPoint(new Vector3 (1.0f, 1.0f, GM .mainCamera. nearClipPlane)).x;
    // Viewポートの一番上のY座標
    GM.startWorldPointY = GM.mainCamera.ViewportToWorldPoint(new Vector3 (0.0f, 0.0f, GM .mainCamera. nearClipPlane)).y;
    // Viewポートの一番下のY座標
    GM.endWorldPointY = GM.mainCamera.ViewportToWorldPoint(new Vector3 (0.0f, 1.0f, GM .mainCamera. nearClipPlane)).y;
}