使用Unity3D将Camera Smooth从UnityScript跟随2D到C＃

Question

I am making a script to be used on the Main Camera object of Unity3D so the camera follows the character in a 2D platformer world.

I tried to translate this from a UnityScript script to c#, I am getting an error in line 26: "Cannot modify a value type return value of 'UnityEngine.Transform.position'. Consider storing the value in a temporary variable."

Original UnityScript Version

var cameraTarget : GameObject;
var player : GameObject;

var smoothTime : float = 0,1;
var cameraFollowX : boolean = true;
var cameraFollowY : boolean = true;
var cameraFollowHeight : boolean = false;
var cameraHeight : float = 2.5;
var velocity : Vector2;
private var thisTransform : Transform;

function Start ()
{
  thisTransform = transform;
}

function Update () 
{

if (cameraFollowX)
{
  thisTransform.position.x = Mathf.SmoothDamp (thisTransform.position.x, cameraTarget.transform.position.x, velocity.x, smoothTime);
}

if (cameraFollowY)
{
  thisTransform.position.y = Mathf.SmoothDamp (thisTransform.position.y, cameraTarget.transform.position.y, velocity.y, smoothTime);
}

if (!cameraFollowX & cameraFollowHeight)
{
  camera.transform.position.y = cameraHeight;
}

}

My C# Version

using UnityEngine;
using System.Collections;

public class CameraSmoothFollow : MonoBehaviour {

    public GameObject cameraTarget; // object to look at or follow
    public GameObject player; // player object for moving

    public float smoothTime = 0.1f; // time for dampen
    public bool cameraFollowX = true; // camera follows on horizontal
    public bool cameraFollowY = true; // camera follows on vertical
    public bool cameraFollowHeight = true; // camera follow CameraTarget object height
    public float cameraHeight = 2.5f; // height of camera adjustable
    public Vector2 velocity; // speed of camera movement

    private Transform thisTransform; // camera Transform

    // Use this for initialization
    void Start () {
        thisTransform = transform;
    }

    // Update is called once per frame
    void Update () {
        if (cameraFollowX){
            thisTransform.position.x = Mathf.SmoothDamp (thisTransform.position.x, cameraTarget.transform.position.x, ref velocity.x, smoothTime); // Here i get the error
        }
        if (cameraFollowY) {
        // to do    
        }
        if (!cameraFollowX & cameraFollowHeight) {
        // to do
        }
    }
}

Any help will be appreciated.

Answer 1

This error occurs because Transform.position is of a value type (probably a struct ). This means that when you access the X property of position , you are accessing a COPY and NOT the real thing. To assign to the position property, you will need to create a new Vector3 and assign it to the position property. Your code will look something like this:

thisTransform.position = new Vector3 (Mathf.SmoothDamp (thisTransform.position.x, cameraTarget.transform.position.x, ref velocity.x, smoothTime), thisTransform.position.y, thisTransform.position.z);

or perhaps more cleaner:

float tempX = new Vector3 (Mathf.SmoothDamp (thisTransform.position.x, cameraTarget.transform.position.x, ref velocity.x, smoothTime);
thisTransform.position = new Vector3 (tempX, thisTransform.position.y, thisTransform.position.z);

Answer 2

You can also use this smooth follow script for both 2d and 3d camera and its very simple.

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);

    }
}
}

got it from github here https://gist.github.com/unity3diy/5aa0b098cb06b3ccbe47

Answer 3

Use FixedUpdate()

If it's Update() the camera jerking will occur.