【Unity3D】血条（HP）

1 需求实现

人机交互Input 中实现了通过键盘控制坦克运动，通过鼠标控制坦克发射炮弹，本文将在此基础上，增加血条（HP）功能。炮弹命中后，HP 值会减少，因此需要应用到刚体组件Rigidbody 和碰撞体组件Collider；从不同角度攻击敌人时，敌人的血条始终朝向相机，因此需要用到相机跟随；血条通过 Image 显示，因此需要用到 UGUI之Image；玩家的血条始终显示在屏幕左上角，因此需要使用到锚点。

1）需求实现

前后箭头键或 W, S 键控制玩家前进和后退；
左右箭头键或 A, D 键控制玩家左右转向；
鼠标左键或空格键控制玩家发射炮弹；
玩家血条显示在屏幕左上角；
相机在玩家后上方的位置，始终跟随玩家，朝玩家正前方看；
玩家移动时，敌人转向玩家，当偏离玩家的角度小于5°时，发射炮弹；
敌人血条显示在其上方，并且始终看向相机。

2）涉及技术栈

2 游戏对象

1）游戏界面

2）游戏对象层级结构

3 Transform组件参数

1）玩家 Transform 组件参数

Name	Type	Position	Rotation	Scale	Color/Texture
Player	Empty	(0, 0.25, -5)	(0, 0, 0)	(1, 1, 1)	#228439FF
Botton	Cube	(0, 0, 0)	(0, 0, 0)	(2, 0.5, 2)	#228439FF
Top	Cube	(0, 0.5, 0)	(0, 0, 0)	(1, 0.5, 1)	#228439FF
Gun	Cylinder	(0, 0, 1.5)	(90, 0, 0)	(0.2, 1, 0.4)	#228439FF
FirePoint	Empty	(0, 1.15, 0)	(0, 0, 0)	(1, 1, 1)	——

补充：Player 游戏对象添加了刚体组件，并修改 Mass = 100，Drag = 1，AngularDrag = 0.1，Freeze Rotation 中勾选 X 和 Z。

2）玩家 HP RectTransform 组件参数

Name	Type	Rect	Width/Height	Pos	Color/Texture
PlayerHP	Canvas	——	——	——	——
Panel	Panel	(0, 0, 0, 0)	——	(-, -, 0)	#FFFFFF00
HealthBG	Image	(0, 0.25, -5)	(200, 20)	(125, -30, 0)	#FFFFFFFF
Health	Image	(0, 0.25, -5)	(200, 20)	(125, -30, 0)	#FF2230FF

补充：玩家 PlayerHP 的 Canvas 渲染模式是 Screen Space - Overlay。

3）敌人 Transform 组件参数

Name	Type	Position	Rotation	Scale	Color/Texture
Enemy	Empty	(0, 0.25, 5)	(0, 180, 0)	(1, 1, 1)	#15D3F9FF
Botton	Cube	(0, 0, 0)	(0, 0, 0)	(2, 0.5, 2)	#15D3F9FF
Top	Cube	(0, 0.5, 0)	(0, 0, 0)	(1, 0.5, 1)	#15D3F9FF
Gun	Cylinder	(0, 0, 1.5)	(90, 0, 0)	(0.2, 1, 0.4)	#15D3F9FF
FirePoint	Empty	(0, 1.15, 0)	(0, 0, 0)	(1, 1, 1)	——

补充：Enemy 游戏对象添加了刚体组件，并修改 Mass = 100，Drag = 0.5，AngularDrag = 0.1，Freeze Rotation 中勾选 X 和 Z。

4）敌人 HP RectTransform 组件参数

Name	Type	Width/Height	Pos	Color/Texture
HP	Canvas	(2, 0.2)	(0, 0.85, 0)	——
HealthBG	Image	(2, 0.2)	(0, 0, 0)	#FFFFFFFF
Health	Image	(2, 0.2)	(0, 0, 0)	#FF2230FF

补充：敌人 HP 的 Canvas 渲染模式是 World Space。

5）地面和炮弹 Transform 组件参数

Name	Type	Position	Rotation	Scale	Color/Texture
Plane	Plane	(0, 0, 0)	(0, 0, 0)	(10, 10, 10)	GrassRockyAlbedo
Bullet	Sphere	(0, 0.5, -5)	(0, 0, 0)	(0.3, 0.3, 0.3)	#228439FF

补充：炮弹作为预设体拖拽到 Assets/Resources/Prefabs 目录下，并且添加了刚体组件。

3 脚本组件

1）CameraController

CameraController.cs

using UnityEngine;
 
public class CameraController : MonoBehaviour {
	private Transform player; // 玩家
	private Vector3 relaPlayerPos; // 相机在玩家坐标系中的位置
	private float targetDistance = 15f; // 相机看向玩家前方的位置
 
	private void Start() {
		relaPlayerPos = new Vector3(0, 4, -8);
		player = GameObject.Find("Player/Top").transform;
	}
 
	private void LateUpdate() {
		CompCameraPos();
	}

	private void CompCameraPos() { // 计算相机坐标
		Vector3 target = player.position + player.forward * targetDistance;
		transform.position = transformVecter(relaPlayerPos, player.position, player.right, player.up, player.forward);
		transform.rotation = Quaternion.LookRotation(target - transform.position);
	}

	// 求以origin为原点, locX, locY, locZ 为坐标轴的本地坐标系中的向量 vec 在世界坐标系中对应的向量
	private Vector3 transformVecter(Vector3 vec, Vector3 origin, Vector3 locX,  Vector3 locY,  Vector3 locZ) {
		return vec.x * locX + vec.y * locY + vec.z * locZ + origin;
	}
}

说明： CameraController 脚本组件挂在 MainCamera 游戏对象上。

2）PlayerController

PlayerController.cs

using System;
using UnityEngine;

public class PlayerController : MonoBehaviour {
	private Transform firePoint; // 开火点
	private GameObject bulletPrefab; // 炮弹预设体
	private float tankMoveSpeed = 4f; // 坦克移动速度
	private float tankRotateSpeed = 2f; // 坦克转向速度
	private float fireWaitTime = float.MaxValue; // 距离上次开火已等待的时间
	private float bulletCoolTime = 0.15f; // 炮弹冷却时间

	private void Start() {
		firePoint = transform.Find("Top/Gun/FirePoint");
		bulletPrefab = (GameObject) Resources.Load("Prefabs/Bullet");
	}

	private void Update() {
		fireWaitTime += Time.deltaTime;
		float hor = Input.GetAxis("Horizontal");
        float ver = Input.GetAxis("Vertical");
		Move(hor, ver);
		if (Input.GetMouseButtonDown(0) || Input.GetKeyDown(KeyCode.Space)) {
			Fire();
		}
	}

	private void Move(float hor, float ver) { // 坦克移动
		if (Math.Abs(hor) > 0.1f || Math.Abs(ver) > 0.1f) {
			GetComponent<Rigidbody>().velocity = transform.forward * tankMoveSpeed * ver;
			GetComponent<Rigidbody>().angularVelocity = Vector3.up * tankRotateSpeed * hor;
		}
	}

	private void Fire() { // 开炮
		if (fireWaitTime > bulletCoolTime) {
			BulletInfo bulletInfo = new BulletInfo("PlayerBullet", Color.red, transform.forward, 10f, 15f);
			GameObject bullet = Instantiate(bulletPrefab, firePoint.position, Quaternion.identity);
			bullet.AddComponent<BulletController>().SetBulletInfo(bulletInfo);
			fireWaitTime = 0f;
		}
	}
}

说明： PlayerController 脚本组件挂在 Player 游戏对象上。

3）EnemyController

EnemyController.cs

using UnityEngine;
using UnityEngine.UI;

public class EnemyController : MonoBehaviour {
	private Transform target; // 目标
	private Transform top; // 炮头
	private Transform firePoint; // 开火点
	private Transform hp; // 血条
	private GameObject bulletPrefab; // 炮弹预设体
	private float rotateSpeed = 0.4f; // 坦克转向速度
	private float fireWaitTime = float.MaxValue; // 距离上次开火已等待的时间
	private float bulletCoolTime = 1f; // 炮弹冷却时间

	private void Start () {
		target = GameObject.Find("Player/Top").transform;
		top = transform.Find("Top");
		firePoint = transform.Find("Top/Gun/FirePoint");
		hp = transform.Find("HP");
		bulletPrefab = (GameObject) Resources.Load("Prefabs/Bullet");
	}

	private void Update () {
		fireWaitTime += Time.deltaTime;
		LookAtTarget();
		float angle = Vector3.Angle(target.position - top.position, top.forward);
		if (LookAtTarget()) {
			Fire();
		}
		HPLookAtCamera();
	}

	private bool LookAtTarget() {
		Vector3 dir = target.position - top.position;
		float angle = Vector3.Angle(dir, top.forward);
		if (angle > 5) {
			int axis = Vector3.Dot(Vector3.Cross(dir, top.forward), Vector3.up) > 0 ? -1 : 1;
			GetComponent<Rigidbody>().angularVelocity = axis * Vector3.up * rotateSpeed;
			return false;
		}
		GetComponent<Rigidbody>().angularVelocity = Vector3.zero;
		return true;
	}

	private void HPLookAtCamera() {
		Vector3 cameraPos = Camera.main.transform.position;
		Vector3 target = new Vector3(cameraPos.x, hp.position.y, cameraPos.z);
		hp.LookAt(target);
	}

	private void Fire() {
		if (fireWaitTime > bulletCoolTime) {
			BulletInfo bulletInfo = new BulletInfo("EnemyBullet", Color.yellow, top.forward, 5f, 10f);
			GameObject bullet = Instantiate(bulletPrefab, firePoint.position, Quaternion.identity); // 通过预设体创建炮弹
			bullet.AddComponent<BulletController>().SetBulletInfo(bulletInfo);
			fireWaitTime = 0;
		}
	}
}

说明： EnemyController 脚本组件挂在 Enemy 游戏对象上。

4）BulletController

BulletController.cs

using UnityEngine;
using UnityEngine.UI;

public class BulletController : MonoBehaviour {
	private BulletInfo bulletInfo; // 炮弹信息
	private volatile bool isDying = false;

	private void Start () {
		gameObject.name = bulletInfo.name;
		GetComponent<MeshRenderer>().material.color = bulletInfo.color;
		float lifeTime = bulletInfo.fireRange / bulletInfo.speed; // 存活时间
		Destroy(gameObject, lifeTime);
	}

	private void Update () {
		transform.GetComponent<Rigidbody>().velocity = bulletInfo.flyDir * bulletInfo.speed;
	}

	private void OnCollisionEnter(Collision other) {
		if (isDying) {
			return;
		}
		if (IsHitEnemy(gameObject.name, other.gameObject.name)) {
			other.transform.Find("HP/Health").GetComponent<Image>().fillAmount -= 0.1f;
			isDying = true;
			Destroy(gameObject, 0.1f);
		} else if (IsHitPlayer(gameObject.name, other.gameObject.name)) {
			GameObject.Find("PlayerHP/Panel/Health").GetComponent<Image>().fillAmount -= 0.1f;
			isDying = true;
			Destroy(gameObject, 0.1f);
		}
	}

	public void SetBulletInfo(BulletInfo bulletInfo) {
		this.bulletInfo = bulletInfo;
	}

	private bool IsHitEnemy(string name, string otherName) { // 射击到敌军
		return name.Equals("PlayerBullet") && otherName.Equals("Enemy");
	}

	private bool IsHitPlayer(string name, string otherName) { // 射击到玩家
		return name.Equals("EnemyBullet") && otherName.Equals("Player");
	}
}

说明： BulletController 脚本组件挂在 Bullet 游戏对象上（代码里动态添加）。

5）BulletInfo

BulletInfo.cs

using UnityEngine;

public class BulletInfo {
	public string name; // 炮弹名
	public Color color; // 炮弹颜色
	public Vector3 flyDir; // 炮弹飞出方向
	public float speed; // 炮弹飞行速度
	public float fireRange; // 炮弹射程

	public BulletInfo(string name, Color color, Vector3 flyDir, float speed, float fireRange) {
		this.name = name;
		this.color = color;
		this.flyDir = flyDir;
		this.speed = speed;
		this.fireRange = fireRange;
	}
}