c# - How can I keep chase camera behind player when player rotates?

I have implemented a follow camera in Unity 3D. However, if the player object rotates, the camera does not rotate with it. To fix this I used RotateAround as follows:

playerRotation = CastPositive(player.EulerAngles.y) //guarantees 0-360
cameraRotation = CastPositive(transform.EulerAngles.y)
difference = playerRotation - cameraRotation
transform.RotateAround(player.position, Vector3.up, difference * time.deltaTime)

This works in general. However at some point the difference snaps from -50 to 210. When this happens, the camera swings in the opposite direction all the way round the player object, instead of continuing on its orbit.

How can I avoid this value jump?

• I've tried clamping the various values to no avail, but maybe I've missed something?


• Quaternions?

Answer

Code provided by Katherine Rix:

// Position camera to follow behind player's head.
private void Follow(){

    // orientation as an angle when projected onto the XZ plane
    // this functionality is modularise into a separate method because
    // I use it elsewhere
    float playerAngle = AngleOnXZPlane (player);

    float cameraAngle = AngleOnXZPlane (transform);

    // difference in orientations
    float rotationDiff = Mathf.DeltaAngle(cameraAngle, playerAngle);

    // rotate around target by time-sensitive difference between these angles
    transform.RotateAround(GetTarget(), Vector3.up, rotationDiff * Time.deltaTime);
}

// Find the angle made when projecting the rotation onto the xz plane.

// You could pass in the rotation as a parameter instead of the transform.
private float AngleOnXZPlane(Transform item){

    // get rotation as vector (relative to parent)
    Vector3 direction = item.rotation * item.parent.forward;

    // return angle in degrees when projected onto xz plane
    return Mathf.Atan2(direction.x, direction.z) * Mathf.Rad2Deg;
}