Unity 使用Vector.Cross()判定方位

using UnityEngine;

using System.Collections;
public class Gazimos : MonoBehaviour
{
    public GameObject player;
    public GameObject NPC;
    void OnDrawGizmos()
    {
        //绘制x,y,z
        Gizmos.color = Color.red;
        Gizmos.DrawLine(Vector3.zero, Vector3.right * 1000);
        Gizmos.DrawLine(Vector3.zero, Vector3.right * -1000);


        Gizmos.color = Color.green;
        Gizmos.DrawLine(Vector3.zero, Vector3.up * 1000);
        Gizmos.DrawLine(Vector3.zero, Vector3.up * -1000);


        Gizmos.color = Color.blue;
        Gizmos.DrawLine(Vector3.zero, Vector3.forward * 1000);
        Gizmos.DrawLine(Vector3.zero, Vector3.forward * -1000);


        //0点到player和NPC
        Gizmos.color = Color.black;
        Gizmos.DrawLine(Vector3.zero, player.transform.position);
        Gizmos.DrawLine(Vector3.zero, NPC.transform.position);


        //绘制player到NPC和player正方向，右方向
        Gizmos.color = Color.cyan;
        Gizmos.DrawLine(NPC.transform .position , player.transform.position);
        Gizmos.DrawLine(player.transform.position, player.transform.position+player .transform .forward *3);
        Gizmos.DrawLine(player.transform.position, player.transform.position + player.transform.right  * 3);


        //player到NPC的向量
        Vector3 P_N = NPC.transform.position - player.transform.position;
        //叉乘
        Vector3 P_NF = Vector3.Cross(player.transform.forward , P_N);
        Vector3 P_NR = Vector3.Cross(player.transform.right , P_N);


        //绘制叉乘的向量 黄色代表左右  灰色代表前后
        Gizmos.color = Color.yellow ;
        Gizmos.DrawLine(player.transform.position ,P_NF+player.transform .position );
        Gizmos.color = Color.gray;
        Gizmos.DrawLine(player.transform.position , P_NR+player .transform .position );


    }

}

黄色代表左右：

叉乘的y>0时，  NPC 在Player 右边

叉乘的y<0时，  NPC 在Player 左边

灰色线代表前后：

叉乘的y>0时，  NPC 在Player 前边

叉乘的y>0时，  NPC 在Player 后边