[游戏开发]Unity实现相机拖拽旋转、平移和缩放

using UnityEngine;
using System.Collections;
using UnityEngine.EventSystems;


public class MouseOrBit : MonoBehaviour
{
    public Transform target;
    public float distance = 10.0f;

    public Vector2 rotationSpeed = new Vector2(250.0f, 120.0f);
    public Vector2 moveSpeed = new Vector2(20.0f, 20.0f);

    float yMinLimit = -20;
    float yMaxLimit = 80;

    private float x = 0.0f;
    private float y = 0.0f;

    void Start()
    {
        var angles = transform.eulerAngles;
        x = angles.y;
        y = angles.x;

        if (GetComponent<Rigidbody>())
        {
            GetComponent<Rigidbody>().freezeRotation = true;
        }
    }

    void LateUpdate()
    {
        DragRotation();
        DragMove();
        Scale();
    }

    void DragRotation()
    {
        if (Input.GetMouseButton(0))
        {
            if (target)
            {
                x += Input.GetAxis("Mouse X") * rotationSpeed.x * 0.02f;
                y -= Input.GetAxis("Mouse Y") * rotationSpeed.y * 0.02f;

                y = ClampAngle(y, yMinLimit, yMaxLimit);

                var rotation = Quaternion.Euler(y, x, 0);
                var position = rotation * new Vector3(0.0f, 0.0f, -distance) + target.position;

                transform.rotation = rotation;
                transform.position = position;
            }
        }
    }

    void DragMove()
    {
        if (Input.GetMouseButton(1))
        {
            float x = -Input.GetAxis("Mouse X") * moveSpeed.x * 0.02f;
            float y = -Input.GetAxis("Mouse Y") * moveSpeed.y * 0.02f;
            Vector3 pos = new Vector3(x, y, 0.0f);
            transform.Translate(pos);
        }
    }

    void Scale()
    {
        if (Input.GetAxis("Mouse ScrollWheel") < 0)
        {
            if (Camera.main.fieldOfView <= 100)
                Camera.main.fieldOfView += 2;
            if (Camera.main.orthographicSize <= 20)
                Camera.main.orthographicSize += 0.5F;
        }
        if (Input.GetAxis("Mouse ScrollWheel") > 0)
        {
            if (Camera.main.fieldOfView > 2)
                Camera.main.fieldOfView -= 2;
            if (Camera.main.orthographicSize >= 1)
                Camera.main.orthographicSize -= 0.5F;
        }
    }

    static float ClampAngle(float angle, float min, float max)
    {
        if (angle < -360)
        {
            angle += 360;
        }
        if (angle > 360)
        {
            angle -= 360;
        }
        return Mathf.Clamp(angle, min, max);
    }
}