CameraShaker.cs

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

// TODO: Is there really anything about this that makes it
// specific to cameras? This logic could be used to shake
// anything.  Only thing tying it to that is the ShakeAllCameras
// functionality but we could work that out by tagging things by
// generic categories, and shaking all objects in a category.
//
public class CameraShaker : MonoBehaviour {

	private static List<CameraShaker> shakers = new List<CameraShaker>();

	public float rotationFactor = 1f;

	float maxMagnitude = 0.0f;
	float timeLeft_s = 0.0f;
	float timeTotal_s = 0.0f;

	// Activate every CameraShaker in the scene.
	//
	// time_s: Time (in seconds) for the shake to take.
	// magnitude: distance (in game units) for the shake to move the camera at its most extreme.
	//
	public static void ShakeAllCameras(float time_s, float magnitude)
	{
		foreach (CameraShaker s in shakers) {
			s.Shake (time_s, magnitude);
		}
	}

	void Start () {

		// Add it to the global list of camera shakers.
		shakers.Add (this);
	}

	void OnDestroy() {
		shakers.Remove (this);
	}

	void Update () {

		// Subtract time until it reaches zero, then the shake is done.  Reset the system.
		timeLeft_s -= Time.deltaTime;
		if (timeLeft_s <= 0.0f) {
			timeLeft_s = 0.0f;
			timeTotal_s = 0.0f;
			maxMagnitude = 0.0f;
		}

		// Set the local position to the shaken offset.
		transform.localPosition = GetOffset ();
		Vector3 rotation = GetRotation(transform.localPosition);
		transform.localRotation = Quaternion.Euler (rotation);
	}

	// Generates a random camera offset based on the current state of the shake.
	//
	Vector2 GetOffset()
	{

		// Default offset is zero -- no shake.
		Vector2 offset = Vector2.zero;

		// If there is a current shake in play.
		if (timeLeft_s > 0f && timeTotal_s > 0f) {

			// Choose a random direction.
			float direction = Random.Range (0.0f, 360.0f);

			// Create a vector (relative to camera orientation) with a random direction rotated around the forward axis.
			offset = Quaternion.AngleAxis (direction, transform.forward) * transform.right;

			// Determine the current effective spread (between 0 and maxSpread) and multiply the offset by that.
			offset *= Mathf.Lerp (0.0f, maxMagnitude, timeLeft_s / timeTotal_s);
		}

		return offset;
	}

	Vector3 GetRotation(Vector2 offset)
	{
		return new Vector3 (offset.y * rotationFactor, offset.x * rotationFactor, 0f);
	}

	// Begin a new shake.
	//
	// time_s: Time (in seconds) for the shake to take.
	// magnitude: distance (in game units) for the shake to move the camera at its most extreme.
	//
	public void Shake(float time_s, float magnitude)
	{
		if (magnitude >= maxMagnitude) {
			maxMagnitude = magnitude;
			timeLeft_s = Mathf.Max(time_s, timeLeft_s);
			timeTotal_s = timeLeft_s;
		}
	}
}