比如2D游戏 地图很大，像植物大战僵尸关卡选择界面，需要对可见的区域进行滑动，缩放等，

1....滑动：通过正交摄像机的orthographicSize和位置和实际大小（可视范围大小），计算出距离世界坐标原点偏移量 来计算出位置

2....缩放，对正交相机的orthographicSize进行修改，达到放缩目的。同样也要计算摄像机实际大小（）可视范围大小）

3.....正交相机大小的算法   摄像机实际视界宽度（米）=size*2*屏幕宽高比

当然该方法不限于正交相机 透视相机也可以利用这种思路来计算，当然还要考虑像素和米的换算关系，以下代码块像素米比例是1，即1像素=1米

using System.Collections;
using System.Collections.Generic;
using UnityEngine;// for map mouse and touch slide and zoom
[RequireComponent(typeof(Camera))]
public class MapCameraSlider : MonoBehaviour
{Camera camera = null;float SCREEN_WIDTH = 1136f;//屏幕宽度float SCREEN_HEIGHT = 640f; // 屏幕高度const float max_allow_width = 1024f * 3f; // 最大允许滑动的宽度const float max_allow_height = 1024f * 3f; // 最大允许滑动的高度float distanceScale;Vector3 pos1;Vector3 pos2;const float SCALEPOSTION = 1f; // 全局位置缩放大小bool touchBeg = false;void Start(){SCREEN_HEIGHT = Screen.height;SCREEN_WIDTH = Screen.width;camera = this.GetComponent<Camera>();if (camera == null){Debug.LogError("need camera component");}}void Update(){if (touchBeg){timeTouch += Time.deltaTime;}// ------------------------------------for mobile touch inputif (Input.touchCount == 1){ // slidevar data = Input.GetTouch(0);this.Slide(data.deltaPosition * SCALEPOSTION);pos1 = Vector3.zero;pos2 = Vector3.zero;distanceScale = 0f;if (data.phase == TouchPhase.Began){StopAllCoroutines();touch_beg = data.deltaPosition * SCALEPOSTION;timeTouch = 0.000001f;touchBeg = true;}if (data.phase == TouchPhase.Ended){touchBeg = false;this.StartAutoSlide(touch_beg, data.position);}}else if (Input.touchCount == 2){// scaletouchBeg = false;var d1 = Input.GetTouch(0);var d2 = Input.GetTouch(1);if (d1.phase == TouchPhase.Began){pos1 = d1.position;distanceScale = Vector3.Distance(pos1, pos2);}if (d2.phase == TouchPhase.Began){pos2 = d2.position;distanceScale = Vector3.Distance(pos1, pos2);}if (pos2 != Vector3.zero && pos2 != Vector3.zero){float dis = Vector3.Distance(pos1, pos2);if (d1.phase == TouchPhase.Moved || d2.phase == TouchPhase.Moved){if (dis > distanceScale){this.ZoomOut(Time.deltaTime * 500f);}else if (dis < distanceScale){this.ZoomIn(Time.deltaTime * 500f);}}distanceScale = dis;}}else{touchBeg = false;pos1 = Vector3.zero;pos2 = Vector3.zero;distanceScale = 0f;}//--------------------------------- for pc mouse input//slideif (Input.GetMouseButton(0)){if (lastMousePos == Vector2.zero){timeTouch = 0.000001f;StopAllCoroutines();lastMousePos = Input.mousePosition;touch_beg = lastMousePos;return;}else{timeTouch += Time.deltaTime;Vector2 pos = Input.mousePosition;this.Slide(1.25f * (pos - lastMousePos));lastMousePos = pos;}}else{if (lastMousePos != Vector2.zero){this.StartAutoSlide(touch_beg, Input.mousePosition);}lastMousePos = Vector2.zero;}//----------------------for pc zoomif (Input.GetAxis("Mouse ScrollWheel") < 0){this.ZoomOut(Time.deltaTime * 500f);this.Slide(0f, 0f);}//Zoom inif (Input.GetAxis("Mouse ScrollWheel") > 0){this.ZoomIn(Time.deltaTime * 500f);this.Slide(0f, 0f);}}float maxtime = 3f;//开始惯性动画void StartAutoSlide(Vector2 orign, Vector2 ended){if (Mathf.Abs(timeTouch) < 0.01f){return;}maxtime = 3f;StopAllCoroutines();Debug.Log("slide map ,speed = " + (Vector2.Distance(orign, ended) / timeTouch / 100f) + "  touchTime=" + timeTouch + " posended" + ended + "  beg" + orign);StartCoroutine(RunSliderAction(ended.x - orign.x, ended.y - orign.y, Vector2.Distance(orign, ended) / timeTouch / 100f));timeTouch = 0.000001f;}Vector2 touch_beg;float timeTouch = 0.000001f;IEnumerator RunSliderAction(float dx, float dy, float speed){float time = 0f;float dis = 0f;while (time < maxtime && speed >= 0f){yield return new WaitForEndOfFrame();time += Time.deltaTime;dis += Time.deltaTime * 0.01f;//  Debug.LogError(pos + "      " + time + "    speed=" + speed);speed -= Time.deltaTime * 10f;this.Slide(Time.deltaTime * speed * dx, dy * Time.deltaTime * speed);}}Vector2 lastMousePos = Vector2.zero;//滑动接口，参数是偏移量void Slide(Vector2 dp){this.Slide(dp.x, dp.y);}//滑动接口，参数是偏移量void Slide(float dx, float dy){dx = -dx;dy = -dy;var pos = transform.position;pos.x += dx;pos.y += dy;transform.position = pos;//实际宽度float real_width = camera.orthographicSize * 2 * SCREEN_WIDTH / SCREEN_HEIGHT;float real_height = real_width * SCREEN_HEIGHT / SCREEN_WIDTH;//process edgeif (transform.position.x <= real_width / 2f){//x leftthis.SetPosX(0);}if (transform.position.x >= max_allow_width - real_width / 2f){// x  rightthis.SetPosX(max_allow_width - real_width);}if (transform.position.y <= real_height / 2f){//  y upthis.SetPosY(0);}if (transform.position.y >= max_allow_height - real_height / 2f){// y downthis.SetPosY(max_allow_height - real_height);}}//放大接口void ZoomOut(float delta){camera.orthographicSize = camera.orthographicSize + delta;float real_width = camera.orthographicSize * 2 * SCREEN_WIDTH / SCREEN_HEIGHT;float real_height = real_width * SCREEN_HEIGHT / SCREEN_WIDTH;float max_size = max_allow_width * SCREEN_HEIGHT / 2f / SCREEN_WIDTH;if (real_width >= max_allow_width){camera.orthographicSize = max_size;}}//缩小接口void ZoomIn(float delta){camera.orthographicSize = camera.orthographicSize - delta;float real_width = camera.orthographicSize * 2 * SCREEN_WIDTH / SCREEN_HEIGHT;float real_height = real_width * SCREEN_HEIGHT / SCREEN_WIDTH;float min_size = 150f;if (camera.orthographicSize <= min_size){camera.orthographicSize = min_size;}}// 设置x偏移量，偏移量是从世界坐标原点开始计算void SetPosX(float offsetX){float real_width = camera.orthographicSize * 2 * SCREEN_WIDTH / SCREEN_HEIGHT;float real_height = real_width * SCREEN_HEIGHT / SCREEN_WIDTH;var posOld = transform.position;transform.position = new Vector3(real_width / 2f + offsetX, posOld.y, posOld.z);}// 设置y偏移量，偏移量是从世界坐标原点开始计算void SetPosY(float offsetY){float real_width = camera.orthographicSize * 2 * SCREEN_WIDTH / SCREEN_HEIGHT;float real_height = real_width * SCREEN_HEIGHT / SCREEN_WIDTH;var posOld = transform.position;transform.position = new Vector3(posOld.x, offsetY + real_height / 2f, posOld.z);}}