巧用Unity 2D功能：只需六步开发简单的2D UFO游戏（collision circle）

无论我们现在可以选择多少种类繁多的，拥有逼真画面感的游戏，2D游戏始终会在玩家们的心中占据一席之地，而对于想迈入开发者行列的同学们来说，先尝试做一款2D游戏无疑是合适的起点。Unity中的2D功能让开发此类游戏更加的便捷，这篇教程将教大家使用Unity 2D功能制作一个非常简单的UFO游戏，整个过程只需要6个步骤，适合Unity初学者以及对Unity的2D功能不甚熟悉的开发者们，希望Unity能让你初尝游戏开发的乐趣，为以后的开发之路奠定基础，你准备好完成这款简单的2D游戏了吗？

第一步新建项目设置场景

首先下载项目所需的资源，或者在Asset Store中下载Unity官方的2D UFO Tutorial。

新建2D项目，在Assets文件夹下新建三个文件夹：Prefabs、Scripts、Scenes。将下载的资源导入项目，会看到Sprites文件夹。将Sprites文件夹下的Background和UFO图片拖拽至层级视图（Hierarchy），将UFO重命名为Player。如下：

依次点击菜单项Edit > Project Settings > Tags and Layers，新建三个Sorting Layer分别命名为Background、Pickups和Players，然后设置各Sprite的Sorting Layer。

将Player的Scale设为(0.75, 0.75, 0)，如下：

将Main Camera的Size设为16.5，背景颜色设为RGB(32, 32, 32)，如下：

将场景保存到新建的Scenes文件夹下，任意命名即可，本例中命名为Main。

第二步添加控制主角的脚本

首先为Player游戏对象添加Rigibody 2D组件。然后新建脚本CompletePlayerController

用于控制Player对象，脚本代码如下：

using UnityEngine;

using System.Collections;

//Adding this allows us to access members of the UI namespace including Text.

using UnityEngine.UI;

public class CompletePlayerController : MonoBehaviour {

public float speed; //Floating point variable to store the player’s movement speed.

public Text countText; //Store a reference to the UI Text component which will display the number of pickups collected.

public Text winText; //Store a reference to the UI Text component which will display the ‘You win’ message.

private Rigidbody2D rb2d; //Store a reference to the Rigidbody2D component required to use 2D Physics.

private int count; //Integer to store the number of pickups collected so far.

// Use this for initialization

void Start()

{

rb2d = GetComponent ();

count = 0; //Initialze winText to a blank string since we haven't won yet at beginning. winText.text = ""; //Call our SetCountText function which will update the text with the current value for count. SetCountText (); }

{
//Store the current horizontal Input in the float moveHorizontal. float moveHorizontal = Input.GetAxis (“Horizontal”);
//Store the current vertical input in the float moveVertical. float moveVertical = Input.GetAxis (“Vertical”);
//Use the two store floats to create a new Vector2 variable movement.
Vector2 movement = new Vector2 (moveHorizontal, moveVertical);
rb2d.AddForce (movement * speed);
}
//OnTriggerEnter2D is called whenever this object overlaps with a trigger collider. void OnTriggerEnter2D(Collider2D other)
{
//Check the provided Collider2D parameter other to see if it is tagged “PickUp”, if it is…
if (other.gameObject.CompareTag (“PickUp”))
{
//… then set the other object we just collided with to inactive. other.gameObject.SetActive(false);
//Add one to the current value of our count variable.
//Update the currently displayed count by calling the SetCountText function. SetCountText ();
}
}
//This function updates the text displaying the number of objects we’ve collected and displays our victory message if we’ve collected all of them. void SetCountText() {
countText.text = “Count: ” count.ToString ();
if (count >= 12)
}
}
依次点击Edit > Project Settings > Input设置控制键，如下：

将Player对象的Rigibody 2D组件的Gravity Scale属性设为0以防止Player向下坠落，并将PlayerController脚本的Speed属性设为10。

第三步添加碰撞

为Player添加Circle Collider 2D组件并将Radius属性设为2.15，如下：

接下来为背景添加碰撞体，让玩家不要跑出墙壁。为背景边框添加4个Box Collider 2D组件，各组件属性设置如下：

第四步让摄像机跟随主角

新建脚本CompleteCameraController绑定到Main Camera上，用于控制相机跟随主角移动。脚本代码如下：

using UnityEngine;
using System.Collections;
public class CompleteCameraController : MonoBehaviour {
//Public variable to store a reference to the player game object
private Vector3 offset;
void Start ()
//Calculate and store the offset value by getting the distance between the player’s position and camera’s position.
offset = transform.position - player.transform.position;
// LateUpdate is called after Update each frame
void LateUpdate ()
// Set the position of the camera’s transform to be the same as the player’s, but offset by the calculated offset distance.
transform.position = player.transform.position offset;
}
}
将Player游戏对象赋给CameraController脚本的player字段。

第五步设置宝石

将Sprites文件夹下的Pickup图片拖拽至层级视图，将其Sorting Layer设为Pickup并添加Circle Collider 2D组件。然后新建脚本CompleteRotator用于旋转宝石，脚本代码如下：

using UnityEngine;
using System.Collections;
//Update is called every frame
{
//Rotate thet transform of the game object this is attached to by 45 degrees, taking into account the time elapsed since last frame.
transform.Rotate (new Vector3 (0, 0, 45) * Time.deltaTime);
}
}

将该游戏对象拖拽至项目视图（Project）的Prefabs文件夹下存为预设体，在层级视图复制出11个宝石对象。然后在层级视图新建GameObject命名为Pickups，并将这12个对象均拖至Pickups下，分别设置合适的位置，如下图：

将Pickup预设体的Tag设为PickUp，并将所有Pickup对象的Circle Collider 2D组件的isTrigger属性勾选上：

第六步添加UI

右键点击层级视图，在弹出菜单中选择UI > Text新建文本，层级视图中除了Text外还会添加Canvas和EventSystem组件。将新建的Text命名为CountText，在检视面板中打开Rect Transform的锚点设置面板后按下Shift＋Alt／Option键点选左上角，让Text自动吸附到界面左上角并选择合适的文本颜色，如下图：