Add README.md

UnityPreviewEditor/README.md

+# UnityPreviewEditor
+
+2222
+UnityPreviewEditor：使用PreviewRenderUtility创建预览窗口。
+
+Unity 版本: Unity 2020.3.18f1c1
+
+### 简介
+1. Example -> PreviewRenderWindow 打开
+2. 效果图：
+
+![](https://gitcode.net/hankangwen/blog-image/-/raw/master/pictures/2022/01/11_21_27_21_20220111212720.png)
+
+### 代码
+```c++
+// PreviewRenderWindow.cs 负责自定义管理界面
+using System.Collections;
+using System.Collections.Generic;
+using UnityEditor;
+using UnityEngine;
+
+public class PreviewRenderWindow : EditorWindow
+{
+    [MenuItem("Example/PreviewRenderWindow")]
+    static void ShowWindow()
+    {
+        GetWindow<PreviewRenderWindow>("PreviewRenderWindow").Show();
+    }
+
+    GameObject _gameObject;
+    GameObject _lastGameObject;
+    PreviewRenderEditor _editor;
+    bool _load = true;
+    Vector2 _lightRot;
+    Vector2 _lastLightRot;
+    
+    void OnGUI()
+    {
+        _gameObject = (GameObject) EditorGUILayout.ObjectField("预览预制体", _gameObject, typeof(GameObject), true);
+        _lightRot = EditorGUILayout.Vector2Field("光源方向", _lightRot);
+        
+        if (_editor == null)
+        {
+            _editor = Editor.CreateEditor(this, typeof(PreviewRenderEditor)) as PreviewRenderEditor;
+        }
+        
+        if(_editor)
+        {
+            if (_lastLightRot != _lightRot)
+            {
+                _lastLightRot = _lightRot;
+                _editor.RefreshLightRot(_lightRot);
+            }
+                
+            _editor.DrawPreview(GUILayoutUtility.GetRect(400, 400));
+        }
+        
+        if (_gameObject && _load)
+        {
+            _editor.RefreshPreviewInstance(_gameObject);
+            _load = false;
+            _lastGameObject = _gameObject;
+        }
+
+        if (_lastGameObject != _gameObject)
+        {
+            _load = true;
+        }
+    }
+}
+```
+
+```c++
+// PreviewRenderEditor.cs 负责预览界面
+using System.Collections;
+using System.Collections.Generic;
+using UnityEditor;
+using UnityEngine;
+
+public class PreviewRenderEditor : Editor
+{
+    private PreviewRenderUtility _previewRenderUtility;
+    private GameObject _previewInstance;
+    private GameObject _targetObj;
+    private static bool _loaded = true;
+    private Vector2 _drag = new Vector2(250f, -30f);
+    private Vector2 _lightRot = new Vector2(180f, 0);
+
+    public void RefreshLightRot(Vector2 rot)
+    {
+        _lightRot = rot;
+    }
+    
+    public void RefreshPreviewInstance(GameObject obj)
+    {
+        _targetObj = obj;
+        if (_previewInstance)
+            UnityEngine.Object.DestroyImmediate(_previewInstance);
+        
+        _previewInstance = null;
+        _loaded = true;
+    }
+
+    private void OnEnable()
+    {
+        if (_previewRenderUtility == null)
+        {
+            _previewRenderUtility = new PreviewRenderUtility();
+        }
+    }
+
+    private void OnDisable()
+    {
+        if (_previewRenderUtility != null)
+        {
+            // 必须进行清理，否则会存在残留对象
+            _previewInstance = null;
+            _previewRenderUtility.Cleanup();
+            _previewRenderUtility = null;
+        }
+    }
+
+    public override void OnPreviewGUI(Rect r, GUIStyle background)
+    {
+        // _loaded	确保只加载一次物体
+        if (_loaded && _targetObj)
+        {
+            _previewInstance = Instantiate(_targetObj as GameObject, Vector3.zero, Quaternion.identity);
+            // AddSingleGO 添加物体
+            _previewRenderUtility.AddSingleGO(_previewInstance);
+            _loaded = false;
+        }
+
+        // 获取拖拽向量
+        _drag = Drag2D(_drag, r);
+        // 事件为绘制时，才进行绘制
+        if (Event.current.type == EventType.Repaint)
+        {
+            _previewRenderUtility.BeginPreview(r, background);
+
+            //调整相机位置与角度
+            Camera camera = _previewRenderUtility.camera;
+            var cameraTran = camera.transform;
+            cameraTran.position = Vector2.zero;
+            cameraTran.rotation = Quaternion.Euler(new Vector3(-_drag.y, -_drag.x, 0));
+            cameraTran.position = cameraTran.forward * -6f;
+            var pos = cameraTran.position;
+            cameraTran.position = new Vector3(pos.x, pos.y + 0.6f, pos.z);
+
+            EditorUtility.SetCameraAnimateMaterials(camera, true);
+
+            camera.cameraType = CameraType.Preview;
+            camera.enabled = false;
+            camera.clearFlags = CameraClearFlags.Skybox;
+            camera.fieldOfView = 30;
+            camera.farClipPlane = 10.0f;
+            camera.nearClipPlane = 2.0f;
+            camera.backgroundColor = new Color(49.0f / 255.0f, 77.0f / 255.0f, 121.0f / 255.0f, 0f);
+
+            // // 设置光源数据
+            _previewRenderUtility.lights[0].intensity = 0.7f;
+            _previewRenderUtility.lights[0].transform.rotation = Quaternion.Euler(_lightRot.x, _lightRot.y, 0f);
+            _previewRenderUtility.lights[1].intensity = 0.7f;
+            _previewRenderUtility.lights[1].transform.rotation = Quaternion.Euler(_lightRot.x, _lightRot.y, 0f);
+            _previewRenderUtility.ambientColor = new Color(0.3f, 0.3f, 0.3f, 0f);
+
+            // camera.transform.LookAt(_previewInstance.transform);
+            // 相机渲染
+            camera.Render();
+            // 结束并绘制
+            _previewRenderUtility.EndAndDrawPreview(r);
+        }
+    }
+
+    // Drag2D 来自源码
+    private static int sliderHash = "Slider".GetHashCode();
+
+    public static Vector2 Drag2D(Vector2 scrollPosition, Rect position)
+    {
+        // 每次获得独一无二的 controlID
+        int controlID = GUIUtility.GetControlID(sliderHash, FocusType.Passive);
+        Event current = Event.current;
+        // 获取对应 controlID 的事件
+        switch (current.GetTypeForControl(controlID))
+        {
+            case EventType.MouseDown:
+            {
+                bool flag = position.Contains(current.mousePosition) && position.width > 50f;
+                if (flag)
+                {
+                    // 鼠标摁住拖出预览窗口外，预览物体任然能够旋转
+                    GUIUtility.hotControl = controlID;
+                    // 采用事件
+                    current.Use();
+                    // 让鼠标可以拖动到屏幕外后，从另一边出来
+                    EditorGUIUtility.SetWantsMouseJumping(1);
+                }
+
+                break;
+            }
+            case EventType.MouseUp:
+            {
+                bool flag2 = GUIUtility.hotControl == controlID;
+                if (flag2)
+                {
+                    GUIUtility.hotControl = 0;
+                }
+
+                EditorGUIUtility.SetWantsMouseJumping(0);
+                break;
+            }
+            case EventType.MouseDrag:
+            {
+                bool flag3 = GUIUtility.hotControl == controlID;
+                if (flag3)
+                {
+                    // shift 加速
+                    scrollPosition -= current.delta * (float) (current.shift ? 3 : 1) /
+                                      Mathf.Min(position.width, position.height) * 140f;
+                    // 以下两条缺少任意一个，会导致延迟更新,拖动过程中无法实时更新
+                    // 直到 repaint事件触发才重新绘制
+                    current.Use();
+                    GUI.changed = true;
+                }
+
+                break;
+            }
+        }
+
+        return scrollPosition;
+    }
+}
+```