按下 左 "Alt" 键， 然后按下鼠标左键旋转场景，按下鼠标右键拖拽场景，滚动鼠标滚轮拉远拉近场景
（实际是摄像机的旋转移动和拉远拉近）
将下脚本直接拖拽到场景中的物体上，运行即可
using UnityEngine;using System.Collections;public class MouseInput : MonoBehaviour{private Vector3 targetPos;protected bool m_bRaycastHit;public float m_fDistance = 8.0f; // 默认距离public float m_fXSpeed = 350.0f; // X 方向速度public float m_fYSpeed = 300.0f; // Y 方向速度public float m_fWheelSpeed = 5.0f; // 默认鼠标滚轮速度public float m_fYMinLimit = -90f; // Y轴最小旋转角度public float m_fYMaxLimit = 90f; // Y轴最大旋转角度private float m_fDistanceMin = 0.10f;private float m_fDistanceMax = 500;public int m_nMoveInputIndex = 1; //1对应右键 public int m_nRotInputIndex = 0; //0对应左键 ，， 2对应中键。public float m_fXRot = 0.0f; // X轴旋转角度public float m_fYRot = 0.0f; // Y轴旋转角度protected Vector3 m_MovePostion;protected Vector3 m_OldMousePos;void OnEnable(){targetPos = Vector3.zero; //m_TargetTrans.position;}void Update(){UpdateDragPosition(Camera.main.transform);UpdateRotate();UpdateCamera();}public void UpdateCamera(){float mouseScroll = Input.GetAxis("Mouse ScrollWheel");if (mouseScroll == 0){return;}m_fDistance = m_fDistance - mouseScroll * m_fWheelSpeed;m_fDistance = Mathf.Clamp(m_fDistance, m_fDistanceMin, m_fDistanceMax);CalculatePosition();}void UpdateRotate(){if (Input.GetMouseButton(m_nRotInputIndex)) //点击鼠标右键{m_fXRot += Input.GetAxis("Mouse X") * m_fXSpeed * 0.02f;// 计算X轴旋转m_fYRot -= Input.GetAxis("Mouse Y") * m_fYSpeed * 0.02f; //计算Y轴旋转m_fYRot = ClampAngle(m_fYRot, m_fYMinLimit, m_fYMaxLimit);//计算旋转角度Quaternion rotation = Quaternion.Euler(m_fYRot, m_fXRot, 0); //转换旋转角度为 QuaternionCamera.main.transform.rotation = rotation; //设置主摄像机的旋转CalculatePosition();}}public float ClampAngle(float angle, float min, float max){if (angle < -360F) angle += 360F;if (angle > 360F) angle -= 360F;return Mathf.Clamp(angle, min, max);}public void CalculatePosition(){Quaternion rotation = Camera.main.transform.rotation; //转换旋转角度为 QuaternionVector3 negDistance = new Vector3(0.0f, 0.0f, -m_fDistance);Vector3 position = rotation * negDistance + targetPos;Camera.main.transform.position = position; //设置主摄像机的位置}void UpdateDragPosition(Transform camera){if (Input.GetMouseButtonDown(m_nMoveInputIndex)) //如果鼠标点击的 1键{m_OldMousePos = Input.mousePosition;}if (Input.GetMouseButton(m_nMoveInputIndex)){Vector3 currMousePos = Input.mousePosition;float worldlen = GetWorldPerScreenPixel(targetPos);m_MovePostion = (m_OldMousePos - currMousePos) * worldlen;m_OldMousePos = currMousePos;camera.Translate(m_MovePostion, Space.Self);}}public static float GetWorldPerScreenPixel(Vector3 worldPoint){Camera cam = Camera.main;if (cam == null)return 0;Plane nearPlane = new Plane(cam.transform.forward, cam.transform.position);float dist = nearPlane.GetDistanceToPoint(worldPoint);float sample = 100;return Vector3.Distance(cam.ScreenToWorldPoint(new Vector3(Screen.width / 2, Screen.height / 2 - sample / 2, dist)), cam.ScreenToWorldPoint(new Vector3(Screen.width / 2, Screen.height / 2 + sample / 2, dist))) / sample;}}
