function ViewportPointToRay (position : Ray
Description描述
Returns a ray going from camera through a viewport point.
返回从相机出发穿过视点的一个射线。
Resulting ray is in world space, starting on the near plane of the camera and going through position's (x,y) coordinates on the viewport (position.z is ignored).
产生的射线是在世界空间中，从相机的近裁剪面开始并穿过视口POSITION(x,y)坐标（position.z被忽略）
Viewport coordinates are normalized and relative to the camera. The bottom-left of the camera is (0,0); the top-right is (1,1).
视窗坐标被规范化，并相对于相机。相机的左下为（0,0）；右上是（1,1）。
using UnityEngine;
using System.Collections;
public class example : MonoBehaviour {
void Update() {
Ray ray = camera.ViewportPointToRay(new Vector3(0.5F, 0.5F, 0));
RaycastHit hit;
if (Physics.Raycast(ray, out hit))
print("I'm looking at " + hit.transform.name);
else
print("I'm looking at nothing!");
}
}// Prints the name of the object camera is directly looking at
//打印相机直接看到物体名称
function Update () {
// Get the ray going through the center of the screen
//获取穿过屏幕中心的射线
var ray : Ray = camera.ViewportPointToRay (Vector3(0.5,0.5,0));
// Do a raycast
//投射
var hit : RaycastHit;
if (Physics.Raycast (ray, hit))
print ("I'm looking at " + hit.transform.name);
else
print ("I'm looking at nothing!");
}