When moving backwards, my sphere flies upwards instead of straight backwards.

I'm trying to make a Super Monkey Ball style movement for my ball so when you change the direction of the camera, the player's position changes to that camera's direction. When I move forward, the camera tilts towards the forward position and the ball moves forward. However, when I move the ball backwards, the ball flies straight up into the air at a 45 degree angle (so not exactly straight up).

Here's an attachment of my code for the camera:

Code (CSharp):

1.  
2. using UnityEngine;
3. using System.Collections;
4.  
5. public class CameraController : MonoBehaviour
6. {
7.  
8.     private GameObject player;
9.     private Vector3 offset;
10.     public float boardTiltMax = 15f; // Maximum angle to tilt the camera to fake the level tilting
11.     private Vector3 desiredPosition;
12.     private GameObject desiredPositionObject;
13.  
14.     private float rotationDamping = 10f;
15.     public float movementDamping = 150f;
16.     private float turnSpeed = 300f;
17.  
18.     private float turnAngle = 0.0f;
19.  
20.     // Use this for initialization
21.     void Start()
22.     {
23.         offset = transform.position;
24.         desiredPosition = transform.position;
25.         desiredPositionObject = new GameObject("cameraFollow");
26.         DontDestroyOnLoad(desiredPositionObject);
27.         desiredPositionObject.transform.position = transform.position;
28.  
29.         // fine the player object
30.         player = GameObject.Find("Player");
31.  
32.         if (player == null)
33.         {
34.  
35.             Debug.LogError("Could not find object \"Player\" ! Aborting GameCamera load.");
36.             DestroyImmediate(gameObject);
37.         }
38.     }
39.  
40.     void Update()
41.     {
42.         // Rotate the camera around the ball to adjust movement when Q or E are pressed (left/right movement)
43.         turnAngle += Input.GetAxis("Horizontal") * turnSpeed * Time.deltaTime;
44.     }
45.  
46.     void LateUpdate()
47.     {
48.         // find the ZX direction from the player to the camera
49.         var heading = transform.position - player.transform.position;
50.         heading.y = 0f;
51.         var distance = heading.magnitude;
52.         var direction = heading / distance;
53.  
54.         // Find the right vector for the diretion
55.         var rotationVectorRight = Vector3.Cross(direction, Vector3.up);
56.  
57.         // Move the camera
58.         desiredPositionObject.transform.position = player.transform.position + offset;
59.  
60.         // Rotate around the players Y axis by the turn value
61.         desiredPositionObject.transform.RotateAround(player.transform.position, Vector3.up, turnAngle);
62.  
63.         // Deal with forward/backward board rotation
64.         desiredPositionObject.transform.RotateAround(player.transform.position, rotationVectorRight, -Input.GetAxisRaw("Vertical") * boardTiltMax);
65.  
66.         // Ensure we're looking at the player before the roll rotation is applied
67.         desiredPositionObject.transform.LookAt(player.transform.position);
68.  
69.         // Apply the roll rotation
70.         desiredPositionObject.transform.RotateAround(desiredPositionObject.transform.position, direction, -Input.GetAxisRaw("Horizontal") * boardTiltMax);
71.  
72.         // Lerp the cameras position to match the target object
73.         transform.position = Vector3.Slerp(transform.position, desiredPositionObject.transform.position, Time.deltaTime * movementDamping);
74.  
75.         // Lerp the cameras rotation to match the target object
76.         transform.rotation = Quaternion.Lerp(transform.rotation,
77.             desiredPositionObject.transform.rotation,
78.             Time.deltaTime * rotationDamping);
79.  
80.         // Re-center the camera on the object to account for new roll rotation
81.         CenterCameraOnTarget();
82.  
83.     }
84.  
85.     private void CenterCameraOnTarget()
86.     {
87.         Plane plane = new Plane(transform.forward, player.transform.position);
88.         Ray ray = GetComponent<Camera>().ScreenPointToRay(new Vector3(Screen.width / 2, Screen.height / 2, 0.0f));
89.         float distance;
90.         plane.Raycast(ray, out distance);
91.  
92.         var point = ray.GetPoint(distance);
93.         var offset = player.transform.position - point;
94.         transform.position += offset;
95.     }
96. }
97.  

Code for the simple movement script:

Code (CSharp):

1.  
2. using UnityEngine;
3. using System.Collections;
4.  
5. public class PlayerController : MonoBehaviour {
6.  
7.     public float speed;
8.  
9.     public GameObject camera;
10.  
11.     private Rigidbody rb;
12.  
13.     void Start()
14.     {
15.         rb = GetComponent<Rigidbody> ();
16.     }
17.  
18.     void FixedUpdate()
19.     {
20.         float movementHorizontal = Input.GetAxis("Horizontal");
21.         float movementVertical = Input.GetAxis("Vertical");
22.  
23.         Vector3 movementVector = new Vector3(movementHorizontal, 0.0f, movementVertical);
24.         movementVector = camera.transform.TransformDirection(movementVector);
25.  
26.         //GetComponent<Rigidbody>().AddForce(movementVector * speed * Time.deltaTime);
27.  
28.         rb.AddForce (movementVector * speed);
29.     }
30. }
31.  

 

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