Keyboard Camera Movement - how to go forward/backward with a rotated transform?

I have a GameObject with a camera component. I've attached the following script. I also have a Plane for a the ground.

Everything is working as expected with the exception of the up and down arrow keys. The are working correctly as coded, that much I understand. The GO transform is rotated a bit so "transform.forward" is pointing down a bit so going forward takes you through the Plane and backward take you out of the plane.

My question is how do I change the code so the camera moves "correctly". I would like the up and down keys to move you along the Plane same as the left and right keys do, regardless of the transforms rotation x.

Code (csharp):

1.  
2. using UnityEngine;
3. using System.Collections;
4.  
5. [RequireComponent (typeof (Camera))]
6. public class WorldEditorCamera : MonoBehaviour {
7.     public Camera cam;
8.  
9.     private float _zoom = 20.0f;
10.     private float _mouseZoomSpeed = 80.0f;
11.    
12.     private float _orbitXSpeed = 240.0f;
13.     private float _orbitYSpeed = 123.0f;
14.     private int _orbitYMin = 35;
15.     private int _orbitYMax = 85;
16.     private float _orbitX = 22.0f;
17.     private float _orbitY = 33.0f;
18.  
19.     private Transform _transform;
20.     private Vector3 _position;
21.     private Light _light;
22.  
23.     public void Start () {
24.         _transform = transform;
25.         _transform.localPosition = new Vector3(0f, 20f, 0f);
26.         _position = _transform.position;
27.  
28.         _orbitX = 22f;
29.         _orbitY = 33f;
30.        
31.         cam = gameObject.GetComponent<Camera>();
32.  
33.         // Make the rigid body not change rotation
34.         if (GetComponent<Rigidbody>())
35.             GetComponent<Rigidbody>().freezeRotation = true;
36.     }
37.  
38.     public void Update () {
39.         // Update position
40.         if(Input.GetKey(KeyCode.RightArrow)) {
41.             _position += _transform.right * _orbitXSpeed * Time.deltaTime;
42.         }
43.         if(Input.GetKey(KeyCode.LeftArrow)) {
44.             _position -= _transform.right * _orbitXSpeed * Time.deltaTime;
45.         }
46.         if(Input.GetKey(KeyCode.UpArrow)) {
47.             _position += _transform.forward * _orbitXSpeed * Time.deltaTime;
48.         }
49.         if(Input.GetKey(KeyCode.DownArrow)) {
50.             _position -= _transform.forward * _orbitXSpeed * Time.deltaTime;
51.         }
52.  
53.         // Update rotation
54.         if (Input.GetKey(KeyCode.A)) {
55.             _orbitX += _orbitXSpeed * 0.02f;
56.         }
57.         else if (Input.GetKey(KeyCode.D)) {
58.             _orbitX -= _orbitXSpeed * 0.02f;
59.         }
60.         if (Input.GetKey(KeyCode.W)) {
61.             _orbitY += _orbitYSpeed * 0.02f;
62.         }
63.         else if (Input.GetKey(KeyCode.S)) {
64.             _orbitY -= _orbitYSpeed * 0.02f;
65.         }
66.         _orbitY = ClampAngle(_orbitY, _orbitYMin, _orbitYMax);
67.  
68.         // Update zoom
69.         _zoom += -Input.GetAxis("Mouse ScrollWheel") * _mouseZoomSpeed * 0.02f;
70.         _zoom = Mathf.Clamp(_zoom, 15, 100);
71.     }
72.    
73.     public void LateUpdate () {
74.         Quaternion rotation = Quaternion.Euler(_orbitY, _orbitX, 0.0f);
75.         Vector3 position = rotation * new Vector3(0.0f, 0.0f, -_zoom) + _position;
76.        
77.         _transform.rotation = rotation;
78.         _transform.position = position;
79.     }
80.    
81.     public static float ClampAngle (float angle, float min, float max) {
82.         if (angle < -360.0f)
83.             angle += 360.0f;
84.         if (angle > 360.0f)
85.             angle -= 360.0f;
86.         return Mathf.Clamp (angle, min, max);
87.     }
88. }
89.  

 

use Vector3.up instead of transform.up for a "Straight up" vector.

Also in ClampAngle you should use modulus

Code (CSharp):

1. angle = angle % 360;
2. return Mathf.Clamp (angle, min, max);
3.  

 

Thanks for the fix with the clamp.

I'm looking for the "Up Arrow" to move the camera forward level with the Plane, not up/down into the air. It still has to reference the transform somehow because the player could have used the "A" or "W" keys to rotate the camera.