视线追逐

本人是一名刚从事游戏行业不久的菜鸟，最近在看《Unity3D人工智能编程精萃》这本书，个人觉得浅显易懂，很适合入门。因此把本人的学习经历和心得纪录下来，还请各路大神多多指教。

1.视线追逐

视线法原理主要是让追击者沿着猎物的前进方向前进，让追击者永远面对着猎物当前的位置追击，当猎物站立不动时，追击者所走的路径是直的，但如果猎物移动时，路径就可能时弯弯曲曲的了。如下图所示：

下面就用Unity3D实现这部分的功能。

编程中主要涉及到3个类Vehicle类,AILocomotion类和Steering类。

Vehicle类实现

using UnityEngine;using System.Collections;public class Vehicle : MonoBehaviour {// 操控行为类;private Steering steerings;// 物体能达到的最大速度;public float maxSpeed = 10;// 施加到物体上力的最大值public float maxForce = 100;protected float sqrMaxSpeed;// 物体的质量public float mass = 1;// 速度public Vector3 velocity;// 转向速度public float damping = 0.9f;// 更新频率public float computeInterval = 0.2f;// 最后计算得到的控制力private Vector3 steeringForce = new Vector3(0,0,0);// 加速度protected Vector3 acceleration;// 计时器private float timer = 0;protected void Init(){steeringForce = new Vector3 (0, 0, 0);sqrMaxSpeed = maxSpeed * maxSpeed;timer = 0;steerings = GetComponent<Steering> ();}// Use this for initializationvoid Start () {}// Update is called once per framevoid Update () {timer += Time.deltaTime;steeringForce = new Vector3 (0, 0, 0);if (timer > computeInterval) {steeringForce += steerings.Force () * steerings.weight;steeringForce = Vector3.ClampMagnitude (steeringForce, maxForce);acceleration = steeringForce / mass;timer = 0;}}}

AILocomotion类

<pre name="code" class="csharp">using UnityEngine;using System.Collections;public class AILocomotion : Vehicle {private CharacterController controller;private Rigidbody theRigidbody;private Vector3 moveDistance;public Animator anim;private AnimatorStateInfo currentBaseState;// Use this for initializationvoid Start () {controller = GetComponent<CharacterController> ();theRigidbody = GetComponent<Rigidbody> ();moveDistance = new Vector3 (0, 0, 0);currentBaseState = anim.GetCurrentAnimatorStateInfo (0);base.Init ();}void FixedUpdate(){velocity += acceleration * Time.fixedDeltaTime;if (velocity.sqrMagnitude > sqrMaxSpeed)velocity = velocity.normalized * maxSpeed;moveDistance = velocity * Time.fixedDeltaTime;velocity.y = 0;moveDistance.y = 0;if (controller != null)controller.SimpleMove (velocity);else if (theRigidbody == null || theRigidbody.isKinematic)transform.position += moveDistance;elsetheRigidbody.MovePosition (theRigidbody.position + moveDistance);if (velocity.sqrMagnitude > 0.00001) {Vector3 newForward = Vector3.Slerp (transform.forward, velocity, damping * Time.deltaTime);newForward.y = 0;transform.forward = newForward;}anim.SetFloat("Forward", maxSpeed, 0.1f, Time.fixedDeltaTime);}}

Steering类

using UnityEngine;using System.Collections;public abstract class Steering : MonoBehaviour {public float weight = 1;// Use this for initializationvoid Start () {}// Update is called once per framevoid Update () {}public virtual Vector3 Force(){return new Vector3 (0, 0, 0);}}

(1)目标静止的情况

编写SteeringForSeek类

using UnityEngine;using System.Collections;public class SteeringForSeek : Steering {public GameObject target;private Vector3 desiredVelocity;private Vehicle m_vehicle;private float maxSpeed;// Use this for initializationvoid Start () {m_vehicle = GetComponent<Vehicle> ();maxSpeed = m_vehicle.maxSpeed;}public override Vector3 Force (){desiredVelocity = (target.transform.position - transform.position).normalized * maxSpeed;desiredVelocity.y = 0;return (desiredVelocity - m_vehicle.velocity);}// Update is called once per framevoid Update () {}}

运行程序，为物体加上Character Controller组件、AILocomotion以及SteeringForSeek脚本。游戏运行如下：

tiantian

程序中使用的人物模型是Standard Assets中的Ethan模型。

工程可以在这里下载到点击打开链接