[unity3d] camera follow

1 Preface

        The camera follows Camera means always following a particular GameObject , There are the following 2 Kinds of following effect ：

• Position follows ： The vector that the camera points to the target GameObject is always the same
• Position and attitude follow ： The coordinates and orientation of the camera in the coordinate system of the target game object remain unchanged

          The simplest way to follow the camera position and attitude is ： Drag the camera GameObject under the target GameObject , That is, the camera is the sub object of the target game object , The principle is ： The position and posture of the child object always change with the change of the parent object , And remain relatively unchanged . This article does not show this approach , The camera position transformation will be controlled by code , Realize the camera following effect .

2 application

2.1 Position follows

        1） The game object

        The object of the game Transform The component parameters are as follows ：

Name	Type	Position	Rotation	Scale	Color/Texture
Plane	Plane	(0, 0, 0)	(0, 0, 0)	(10, 10, 10)	GrassRockyAlbedo
Tank	Empty	(0, 0.25, -5)	(0, 0, 0)	(1, 1, 1)	——
Button	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

         The hierarchy of the game object is as follows ：

         2） Script components

        Tank.cs

using UnityEngine;

public class Tank : MonoBehaviour {

	void Update () {
		float hor = Input.GetAxis("Horizontal");
        float ver = Input.GetAxis("Vertical");
		transform.Translate(0, 0, ver * Time.deltaTime * 3);
		transform.Rotate(Vector3.up * hor * Time.deltaTime * 120f);
	}
}

        explain ：Tank.cs The script component is hung on Tank On the object of the game . 

        CameraFollow.cs

using UnityEngine;

public class CameraFollow : MonoBehaviour {
	private Transform player; //  The player 
	private Vector3 dir; //  The direction vector from the initial camera to the target tank 

	void Start() {
		player = GameObject.Find("Tank").transform;
		dir = player.position - transform.position;
	}

	void Update () {
		transform.position = player.position - dir;
	}
}

         explain ：CameraFollow.cs The script component is hung on Main Camera On the object of the game .  

        3） Running effect

2.2 Position and attitude follow

        The game object is its Transform Component parameters are the same as 2.1 section ,.

        1） Script components

        Tank.cs Script components are the same as 2.1 section .

        CameraFollow.cs

using UnityEngine;

public class CameraFollow : MonoBehaviour {
	private Transform player; //  The player 
	private Vector3 dir; //  The direction vector from the initial camera to the target tank 

	void Start() {
		player = GameObject.Find("Tank").transform;
		dir = player.position - transform.position;
	}

	void Update () {
		transform.position = transformVecter(-dir, player.position, player.right, player.up, player.forward);
		transform.rotation = Quaternion.LookRotation(player.position - transform.position);
	}

	//  Seeking for origin Origin , locX, locY, locZ  Is the vector in the local coordinate system of the coordinate axis  vec  The corresponding vector in the world coordinate system 
	private Vector3 transformVecter(Vector3 vec, Vector3 origin, Vector3 locX,  Vector3 locY,  Vector3 locZ) {
		return vec.x * locX + vec.y * locY + vec.z * locZ + origin;
	}
}

         2） Running effect