How do I make a camera follow an object in unity3d C#?

Question

I have an object called Ball, and I added keyboard interactivity to it(WASD to move the ball) I need the camera to stay behind and follow the ball, but I am getting errors.

using UnityEngine;
using System.Collections;
public class ballmain : MonoBehaviour {
    public bool isMoving = false;
    public string direction;
    public float camX;
    public float camY;
    public float camZ;
    // Use this for initialization
    void Start () {
        Debug.Log("Can this run!!!");
    }

    // Update is called once per frame
    void Update () {
        camX = rigidbody.transform.position.x -=10;
        camY = rigidbody.transform.position.y -=10;
        camZ = rigidbody.transform.position.z;
        camera.transform.position = new Vector3(camX, camY, camZ);
            //followed by code that makes ball move
    }
}

I get error "Assets/ballmain.cs(18,44): error CS1612: Cannot modify a value type return value of 'UnityEngine.Transform.position'. Consider storing the value in a temporary variable" Does anyone know the answer? If I comment out the code about the camera the ball can move around.

Answer 1

here you go . a full code.

Simple Following

using UnityEngine;
using System.Collections;

public class Follow: MonoBehaviour {
public Transform target;
public float smooth= 5.0f;
void  Update (){
    transform.position = Vector3.Lerp (
        transform.position, target.position,
        Time.deltaTime * smooth);
} 

    } 

Advanced Following

using UnityEngine;
using System.Collections;

public class SmoothFollowScript: MonoBehaviour {

// The target we are following
public  Transform target;
// The distance in the x-z plane to the target
public int distance = 10.0;
// the height we want the camera to be above the target
public int height = 10.0;
// How much we 
public heightDamping = 2.0;
public rotationDamping = 0.6;


void  LateUpdate (){
    // Early out if we don't have a target
    if (TargetScript.russ == true){
    if (!target)
        return;

    // Calculate the current rotation angles
    wantedRotationAngle = target.eulerAngles.y;
    wantedHeight = target.position.y + height;

    currentRotationAngle = transform.eulerAngles.y;
    currentHeight = transform.position.y;

    // Damp the rotation around the y-axis
    currentRotationAngle = Mathf.LerpAngle (currentRotationAngle, wantedRotationAngle, rotationDamping * Time.deltaTime);

    // Damp the height
    currentHeight = Mathf.Lerp (currentHeight, wantedHeight, heightDamping * Time.deltaTime);

    // Convert the angle into a rotation
    currentRotation = Quaternion.Euler (0, currentRotationAngle, 0);

    // Set the position of the camera on the x-z plane to:
    // distance meters behind the target
    transform.position = target.position;
    transform.position -= currentRotation * Vector3.forward * distance;

    // Set the height of the camera
    transform.position.y = currentHeight;

    // Always look at the target
    transform.LookAt (target);
}
}
}

Answer 2

如果你只是想跟随目标物体按照你想要的方式对准相机的位置，并使相机成为目标物体的孩子，其余的将做

Answer 3

Include Standard Mobile Asset to your project. It contains a SmoothFollow2D.js code in its script section. Attach this code with the gameobject and initialize public variables. This will simply do the job for you.

Answer 4

I found this simple and useful unity 2d camera follow script.

using UnityEngine;
using System.Collections;

public class FollowCamera : MonoBehaviour {

public float interpVelocity;
public float minDistance;
public float followDistance;
public GameObject target;
public Vector3 offset;
Vector3 targetPos;
// Use this for initialization
void Start () {
    targetPos = transform.position;
}

// Update is called once per frame
void FixedUpdate () {
    if (target)
    {
        Vector3 posNoZ = transform.position;
        posNoZ.z = target.transform.position.z;

        Vector3 targetDirection = (target.transform.position - posNoZ);

        interpVelocity = targetDirection.magnitude * 5f;

        targetPos = transform.position + (targetDirection.normalized * interpVelocity * Time.deltaTime); 

        transform.position = Vector3.Lerp( transform.position, targetPos + offset, 0.25f);

    }
   }
}

source unity2d camera follow script

Answer 5

Here're one script I found useful during my game development. I didn't create them so I give credit to wiki.unity3d.com for providing this amazing script.

Smooth Follow:

using UnityEngine;
using System.Collections;

        public class SmoothFollow2 : MonoBehaviour {
        public Transform target;
        public float distance = 3.0f;
        public float height = 3.0f;
        public float damping = 5.0f;
        public bool smoothRotation = true;
        public bool followBehind = true;
        public float rotationDamping = 10.0f;

        void Update () {
               Vector3 wantedPosition;
               if(followBehind)
                       wantedPosition = target.TransformPoint(0, height, -distance);
               else
                       wantedPosition = target.TransformPoint(0, height, distance);

               transform.position = Vector3.Lerp (transform.position, wantedPosition, Time.deltaTime * damping);

               if (smoothRotation) {
                       Quaternion wantedRotation = Quaternion.LookRotation(target.position - transform.position, target.up);
                       transform.rotation = Quaternion.Slerp (transform.rotation, wantedRotation, Time.deltaTime * rotationDamping);
               }
               else transform.LookAt (target, target.up);
         }
}

More information about my work

Answer 6

The -= in these lines:

   camX = rigidbody.transform.position.x -=10;
   camY = rigidbody.transform.position.y -=10;

is wrong. The -= will attempt to modify the rigidbody.transform.position . You just want - .

However, as it stands, the camera won't track changes in the target's Z position, nor will it track properly if the camera is rotated. To get the correct position you need (in vectors):-

cam_pos = target_pos - dist_to_target * cam_look_at