7. 通过鼠标右键改变视角

using UnityEngine;
using System.Collections;

/// MouseLook rotates the transform based on the mouse delta.
/// Minimum and Maximum values can be used to constrain the possible rotation

/// To make an FPS style character:
/// - Create a capsule.
/// - Add the MouseLook script to the capsule.
///   -> Set the mouse look to use LookX. (You want to only turn character but not tilt it)
/// - Add FPSInputController script to the capsule
///   -> A CharacterMotor and a CharacterController component will be automatically added.

/// - Create a camera. Make the camera a child of the capsule. Reset it's transform.
/// - Add a MouseLook script to the camera.
///   -> Set the mouse look to use LookY. (You want the camera to tilt up and down like a head. The character already turns.)
[AddComponentMenu("Camera-Control/Mouse Look")]
public class MouseLook : MonoBehaviour {

    public enum RotationAxes { MouseXAndY = 0, MouseX = 1, MouseY = 2 }
    public RotationAxes axes = RotationAxes.MouseXAndY;
    public float sensitivityX = 15F;
    public float sensitivityY = 15F;

    public float minimumX = -360F;
    public float maximumX = 360F;

    public float minimumY = -60F;
    public float maximumY = 60F;

    float rotationY = 0F;

    void Update()
    {
        //是否按下鼠标右键
        if (Input.GetMouseButton(1))  
            if (axes == RotationAxes.MouseXAndY)
            {
                float rotationX = transform.localEulerAngles.y + Input.GetAxis("Mouse X") * sensitivityX;

                rotationY += Input.GetAxis("Mouse Y") * sensitivityY;
                rotationY = Mathf.Clamp(rotationY, minimumY, maximumY);

                transform.localEulerAngles = new Vector3(-rotationY, rotationX, 0);
            }
            else if (axes == RotationAxes.MouseX)
            {
                transform.Rotate(0, Input.GetAxis("Mouse X") * sensitivityX, 0);             
            }
            else
            {
                rotationY += Input.GetAxis("Mouse Y") * sensitivityY;
                rotationY = Mathf.Clamp(rotationY, minimumY, maximumY);

                transform.localEulerAngles = new Vector3(-rotationY, transform.localEulerAngles.y, 0);
            }
        else
            ;
    }
    
    void Start ()
    {
        // Make the rigid body not change rotation
        if (rigidbody)
            rigidbody.freezeRotation = true;
    }
}