ObjectViewer for 3d models in 3d space. The concept is based off of Tomb Raider and Skyrim respectively.

ObjectViewer.cs

using UnityEngine;
using System.Collections;

public class ObjectViewer : MonoBehaviour {

	// Object or Transform which we want to rotate
	public Transform targetObject;

	// these are the import but hush hush settings for the rotation properties
	public RotationProperties rotationProperties;
	private float xDeg;
	private float yDeg;
	private Quaternion fromRotation;
	private Quaternion toRotation;

	// we store our rotation settings in a class to seperate them
	[System.Serializable]
	public class RotationProperties
	{
		// rotation speed
		public int speed = 10;
		// rotation friction
		public float friction = 1;
		// rotation smoothing speed
		public float lerpSpeed = 10;
	}

	// secret secret zoom settings
	public ZoomProperties zoomProperties;
	private Vector3 position;
	private float toPosition;

	// now we seperate the zoom settings
	[System.Serializable]
	public class ZoomProperties
	{
		// this value should always be the lowest of the two
		public float minZ = -7.5f;
		// this value should be the highest (even when negative should be the highest or in this case lowest negative value)
		public float maxZ = -2.5f;
		// speed of scroll
		public int speed = 1;
		// zoom smoothing speed
		public float lerpSpeed = 1;
	}

	// on Update... of course
	void Update () {
		// if the target isn't null then we run our code
		if (targetObject != null) {
			// on left mouse button pressed..
			if (Input.GetMouseButton (0)) {
				// we apply our x rotation using a little bit of math into our variable
				xDeg -= Input.GetAxis ("Mouse X") * rotationProperties.speed * rotationProperties.friction;
				// we apply our y rotation using a little bit of math into our variable
				yDeg += Input.GetAxis ("Mouse Y") * rotationProperties.speed * rotationProperties.friction;
				// we store the targets current rotation
				fromRotation = targetObject.rotation;
				// our new rotation with the new values
				toRotation = Quaternion.Euler (yDeg, xDeg, 0);
				// now apply our new values to our object
				targetObject.rotation = Quaternion.Lerp (fromRotation, toRotation, Time.deltaTime * rotationProperties.lerpSpeed);
			}

			// we get the current position of the camera
			position = Camera.main.transform.localPosition;
			// we should set our new position to old first, for relative math then apply our scroll wheel value and speed setting
			toPosition = position.z += Input.GetAxis("Mouse ScrollWheel") * zoomProperties.speed;
			// now we use Lerp, to smooth our zoom speed (or more precisely our position as it slides forward and back)
			position.z = Mathf.Lerp(position.z, toPosition, Time.deltaTime * zoomProperties.lerpSpeed);
			// now we apply a clamp, so that it never goes beyond what the limitations we place
			position.z = Mathf.Clamp(position.z,zoomProperties.minZ,zoomProperties.maxZ);
			// now we set the new values to the object
			Camera.main.transform.localPosition = position;
		}
	}
}