Camera follow rotating ball - ortogonal direction

Question

I have a ball, that has been moved via addForce. It colides in the scene with objects, leading to rotation in all axes.

I want a camera to follow this ball but from the side (direction ortogonal to the move vector and UP vector). No matter what I do, I cannot get this working. The closest I get is almost correct, but camera "bumps" during frames.

I have used this in camera script to attach camera to the ball and move it with it:

this.transform.LookAt(this.cannonBall.transform.position, Vector3.up);

this.transform.position = ball.transform.position;

No I need to rotate camera 90 degree aroun up axis and move it a little backward to track ball from the side.

How can I achive this? If I use

this.transform.Rotate(Vector3.up, 90, Space.World);

It mess up lookAt

Answer 1

Try something like:

public GameObject ball;
public float distanceBack = 6;

private void LateUpdate() {
    //Manually change to the starting angle you want here:
    transform.rotation = Quaternion.identity;

    transform.position = ball.transform.position - transform.TransformDirection(Vector3.back * distanceBack);
    transform.LookAt(ball.transform);
}

Answer 2

You can add this script to the camera, and plug in the ball as the target to be followed. Then just set your offsets.

FYI, I wrote this script in Unity 4.x, so it will ask you if it's all good, so just say yes and it will auto-update.

using UnityEngine;
using System.Collections;

public class TargetFollower : MonoBehaviour
{

    [Tooltip("Target to be followed")]
    public Transform Target;
    [Tooltip("Mimic the Target's changes in x coordinate")]
    public bool FollowTargetX = true;
    [Tooltip("Mimic the Target's changes in y coordinate")]
    public bool FollowTargetY = true;
    [Tooltip("Mimic the Target's changes in z coordinate")]
    public bool FollowTargetZ = true;

    // Update is called once per frame
    void FixedUpdate()
    {
        if (Target)
        {
            Vector3 targetMovement = GetTargetMovement();
            UpdatePosition(targetMovement);
        }
    }

    private Vector3 oldTargetPosition;
    private Vector3 GetTargetMovement()
    {
        if (oldTargetPosition == Vector3.zero)
        {
            oldTargetPosition = Target.transform.position;
        }
        Vector3 newTargetPosition = Target.transform.position;
        Vector3 targetMovement = newTargetPosition - oldTargetPosition;
        oldTargetPosition = new Vector3(newTargetPosition.x, newTargetPosition.y, newTargetPosition.z);
        return targetMovement;
    }

    private void UpdatePosition(Vector3 targetMovement)
    {
        float xPosition = transform.position.x;
        float yPosition = transform.position.y;
        float zPosition = transform.position.z;
        if (FollowTargetX)
        {
            xPosition += targetMovement.x;
        }
        if (FollowTargetY)
        {
            yPosition += targetMovement.y;
        }
        if (FollowTargetZ)
        {
            zPosition += targetMovement.z;
        }
        Vector3 updatedPosition = new Vector3(xPosition, yPosition, zPosition);
        transform.position = updatedPosition;
    }
}