判断是否有敌人的3种方法

 //1、只攻击正前方的单位，向前发射一条射线，攻击碰到的单位
 RaycastHit hit;
 //range 射线的长度，即攻击范围，maskTarget敌方单位的mask，只攻击敌方单位
 if(Physics.Raycast(unit.thisT.position, unit.thisT.forward, out hit, range, maskTarget)){
 Unit targetTemp=hit.collider.gameObject.GetComponent();
 if(targetTemp!=null && targetTemp.HPAttribute.HP>0){
 target=targetTemp;
 if(attackMode==_AttackMode.StopNAttack){
 if(attackMethod!=_AttackMethod.Melee) unit.StopAnimation();
 unit.StopMoving();
 }
 }
 }

 //2、以己方单位为圆心的某一半径长度内

 //返回相交球的所有碰撞体
 Collider[] cols=Physics.OverlapSphere(unit.thisT.position, range, maskTarget);
 //if(cols!=null && cols.Length>0) Debug.Log(cols[0]);
 if(cols.Length>0){
 Collider currentCollider=cols[Random.Range(0, cols.Length)];
 Unit targetTemp=currentCollider.gameObject.GetComponent();
 if(targetTemp!=null && targetTemp.HPAttribute.HP>0){
 target=targetTemp;
 if(attackMode==_AttackMode.StopNAttack){
 if(attackMethod!=_AttackMethod.Melee) unit.StopAnimation();
 unit.StopMoving();
 }
 }
 }

 //3、以己方单位为圆心的扇形范围内
 Collider[] cols=Physics.OverlapSphere(unit.thisT.position, range, maskTarget);
 //if(cols!=null && cols.Length>0) Debug.Log(cols[0]);
 if(cols.Length>0){
 Collider currentCollider=cols[0];
 foreach(Collider col in cols){
 Quaternion targetRot=Quaternion.LookRotation(col.transform.position-unit.thisT.position);
 if(Quaternion.Angle(targetRot, unit.thisT.rotation)
 Unit targetTemp=currentCollider.gameObject.GetComponent();
 if(targetTemp!=null && targetTemp.HPAttribute.HP>0){
 target=targetTemp;
 if(attackMode==_AttackMode.StopNAttack){
 if(attackMethod!=_AttackMethod.Melee) unit.StopAnimation();
 unit.StopMoving();
 }
 break;
 }
 }
 }
 }

http://blog.csdn.net/fzhlee/article/details/8891711