Camera.WorldToViewportPoint 世界转视窗位置

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
	public Transform target;
	void Update() {
		Vector3 viewPos = camera.WorldToViewportPoint(target.position);
		if (viewPos.x > 0.5F)
			print("target is on the right side!");
		else
			print("target is on the left side!");
	}
}

// Finds out whether target is on the left or right side of the screen
//Target在屏幕的左边还是右边
var target : Transform;

function Update () {
	var viewPos : Vector3 = camera.WorldToViewportPoint (target.position);
	// viewport coordinates range from zero to one
	//视口坐标范围从0到1
	if( viewPos.x > 0.5 )
		print ("target is on the right side!");
	else
		print ("target is on the left side!");
	}