CameraFollow.cs

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

public class CameraFollow : MonoBehaviour
{
	private const float BOUNDING_BOX_PADDING = 1.5f;
	private const float MINIMUM_ORTHO_SIZE = 3f;
	private const float ZOOM_SPEED = 5f; //NEVER FORGET, I AM THE FASTEST MAN ALIVE


	public Spawner mSpawner;
	public float mDampTime = 0.15f;
	public BoxCollider2D mLevelBounds;
	private Vector3 mVelocity = Vector3.zero;
	private Camera mCamera;

	// Use this for initialization
	void Start ()
	{
		mCamera = GetComponent<Camera> ();
	}
	
	// LastUpdate is called at the end of the update loop
	void LateUpdate ()
	{
		Rect boundingBox = CalculateBoundingBox ();
		Vector3 targetPosition = CalculateCameraPosition (boundingBox);
		mCamera.orthographicSize = CalculateOrthographicSize (boundingBox);

    //Make sure our camera isn't bigger than our level boundary
		if (mCamera.orthographicSize > mLevelBounds.bounds.extents.y)
		{
			mCamera.orthographicSize = mLevelBounds.bounds.extents.y;
		}

		transform.position = Vector3.SmoothDamp (transform.position, targetPosition, ref mVelocity, mDampTime);
    
    //If we're showing things outside the level, move the camera
		if (transform.position.y - mCamera.orthographicSize < mLevelBounds.bounds.min.y)
		{
			transform.position = new Vector3 (transform.position.x, mLevelBounds.bounds.min.y + mCamera.orthographicSize, transform.position.z);
		}
		if (transform.position.y + mCamera.orthographicSize > mLevelBounds.bounds.max.y)
		{
			transform.position = new Vector3 (transform.position.x, mLevelBounds.bounds.max.y - mCamera.orthographicSize, transform.position.z);
		}
		if (transform.position.x + mCamera.orthographicSize * mCamera.aspect > mLevelBounds.bounds.max.x)
		{
			transform.position = new Vector3 (mLevelBounds.bounds.max.x - mCamera.orthographicSize * mCamera.aspect, transform.position.y, transform.position.z);
		}
		if (transform.position.x - mCamera.orthographicSize * mCamera.aspect < mLevelBounds.bounds.min.x)
		{
			transform.position = new Vector3 (mLevelBounds.bounds.min.x + mCamera.orthographicSize * mCamera.aspect, transform.position.y, transform.position.z);
		}
	}

  //Calculates a bounding box around all the active players.
	private Rect CalculateBoundingBox ()
	{
		float minX = Mathf.Infinity;
		float maxX = Mathf.NegativeInfinity;
		float minY = Mathf.Infinity;
		float maxY = Mathf.NegativeInfinity;

    //ZeroController is my character controller class. I just need the positions of the active players here.
		List<ZeroController> activePlayers = mSpawner.GetActivePlayers ();

		foreach (ZeroController controller in activePlayers)
		{
			Vector3 position = controller.transform.position;

			minX = Mathf.Min (minX, position.x);
			maxX = Mathf.Max (maxX, position.x);
			minY = Mathf.Min (minY, position.y);
			maxY = Mathf.Max (maxY, position.y);
		}

		return Rect.MinMaxRect (minX - BOUNDING_BOX_PADDING, maxY + BOUNDING_BOX_PADDING, maxX + BOUNDING_BOX_PADDING, minY - BOUNDING_BOX_PADDING);
	}

  //Gets the camera position, which is the bounding box's center x/y coords, and the camera's z coord.
	private Vector3 CalculateCameraPosition (Rect boundingBox)
	{
		Vector2 boundingBoxCenter = boundingBox.center;

		return new Vector3 (boundingBoxCenter.x, boundingBoxCenter.y, transform.position.z);
	}
  
  //Calculates the orthographic size of the camera.
	private float CalculateOrthographicSize (Rect boundingBox)
	{
		float orthoSize = mCamera.orthographicSize;

		if (Mathf.Abs (boundingBox.width / mCamera.aspect) > Mathf.Abs (boundingBox.height))
		{
			orthoSize = Mathf.Abs (boundingBox.width) / mCamera.aspect / 2f;
		}
		else
		{
			orthoSize = Mathf.Abs (boundingBox.height) / 2f;
		}

		return Mathf.Clamp (Mathf.Lerp (mCamera.orthographicSize, orthoSize, Time.deltaTime * ZOOM_SPEED), MINIMUM_ORTHO_SIZE, Mathf.Infinity);

	}

}