Parallaxing.cs

using UnityEngine;
using System.Collections;

public class Parallaxing : MonoBehaviour {

    public Transform[] backgrounds;             // Array (list) of all the back- and foregrounds to be parallaxed.
    private float[] parallaxScales;             // Proportion of the camera's movement to move the backgrounds by.
    public float smoothing = 1f;                // How smooth the parallax is going to be. Make sure to set this above 0.

    private Transform cam;                      // Reference to the main camera's Transform.
    private Vector3 previousCamPos;             // Stores the position of the camera in the previous frame.

    // Is called before Start(). Great for references between scripts and objects.
    void Awake ()
    {
        // Set up the camera reference.
        cam = Camera.main.transform;
    }


	// Use this for initialization
	void Start ()
    {
        // The previous frame had the current frame's camera position.
        previousCamPos = cam.position;

        // Assigning corresponding parallexScales.
        parallaxScales = new float[backgrounds.Length];
        for (int i = 0; i < backgrounds.Length; i++)
        {
            parallaxScales[i] = backgrounds[i].position.z * -1;
        }
	}
	
	// Update is called once per frame
	void Update ()
    {
	    // For each background
        for (int i = 0; i < backgrounds.Length; i++)
        {
            // The parallax is the opposite of the camera movement because the previous frame is multiplied by the scale.
            float parallax = (previousCamPos.x - cam.position.x) * parallaxScales[i];

            // Set a target x position which is the current position + the parallax.
            float backgroundTargetPosX = backgrounds[i].position.x + parallax;

            // Create a target position which is the background's current position with its targets x-position.
            Vector3 backgroundTargetPos = new Vector3(backgroundTargetPosX, backgrounds[i].position.y, backgrounds[i].position.z);

            // Fade between current position and the target position with 'lerp'. deltaTime converts frames to seconds.
            backgrounds[i].position = Vector3.Lerp(backgrounds[i].position, backgroundTargetPos, smoothing * Time.deltaTime);
        }

        // Set previousCamPos to the camera's position at the end of the frame.
        previousCamPos = cam.position;
	}
}