using UnityEngine;

public class PreviewExample : MonoBehaviour
{
}

using UnityEngine;
using UnityEditor;

[CustomEditor(typeof(PreviewExample))]
public class PreviewExampleInspector : Editor
{
    private PreviewRenderUtility m_PreviewUtility;
    private GameObject m_PreviewInstance;
    // 預(yù)覽對象的包圍盒
    private Bounds m_PreviewBounds;
    // 預(yù)覽的方向
    private Vector2 m_PreviewDir = new Vector2(120f, -20f);


    public override bool HasPreviewGUI()
    {
        return true;
    }

    public override GUIContent GetPreviewTitle()
    {
        return new GUIContent("預(yù)覽");
    }

    private void AddSingleGO(GameObject go)
    {
#if UNITY_2017_1_OR_NEWER
        m_PreviewUtility.AddSingleGO(go);
#endif
    }


    public override void OnPreviewSettings()
    {
        GUILayout.Label("文本", "preLabel");
        GUILayout.Button("按鈕", "preButton");
    }

    public override void OnPreviewGUI(Rect r, GUIStyle background)
    {
        InitPreview();

        // 上下左右的旋轉(zhuǎn)
        m_PreviewDir = Drag2D(m_PreviewDir, r);
        if (Event.current.type != EventType.Repaint)
        {
            return;
        }

        m_PreviewUtility.BeginPreview(r, background);
        Camera camera = m_PreviewUtility.camera;

        float num = Mathf.Max(m_PreviewBounds.extents.magnitude, 0.0001f);
        float num2 = num * 3.8f;
        Quaternion quaternion = Quaternion.Euler(-m_PreviewDir.y, -m_PreviewDir.x, 0f);
        Vector3 position = m_PreviewBounds.center - quaternion * (Vector3.forward * num2);
        camera.transform.position = position;
        camera.transform.rotation = quaternion;
        camera.nearClipPlane = num2 - num * 1.1f;
        camera.farClipPlane = num2 + num * 1.1f;

        SetEnabledRecursive(m_PreviewInstance, true);
        camera.Render();
        SetEnabledRecursive(m_PreviewInstance, false);
        m_PreviewUtility.EndAndDrawPreview(r);
    }

    private void InitPreview()
    {
        if (m_PreviewUtility == null)
        {
            // 參數(shù)true代表繪制場景內(nèi)的游戲?qū)ο?            m_PreviewUtility = new PreviewRenderUtility(true);
            // 設(shè)置攝像機(jī)的一些參數(shù)
            m_PreviewUtility.cameraFieldOfView = 60f;

            // 創(chuàng)建預(yù)覽的游戲?qū)ο?            CreatePreviewInstances();
        }
        m_PreviewUtility.camera.cullingMask = 1 << kPreviewCullingLayer;
    }

    private void DestroyPreview()
    {
        if (m_PreviewUtility != null)
        {
            // 務(wù)必要進(jìn)行清理，才不會殘留生成的攝像機(jī)對象等
            m_PreviewUtility.Cleanup();
            m_PreviewUtility = null;
        }
    }

    private void DestroyPreviewInstances()
    {
        if (m_PreviewInstance != null)
        {
            DestroyImmediate(m_PreviewInstance);
        }
        m_PreviewInstance = null;
    }

    void OnDestroy()
    {
        DestroyPreviewInstances();
        DestroyPreview();
    }

    private void CreatePreviewInstances()
    {
        DestroyPreviewInstances();

        // 查找要繪制的游戲?qū)ο?        m_PreviewInstance = GameObject.Find("ThirdPerson");
        if(m_PreviewInstance == null)
        {
            return;
        }

        // 實(shí)例化對象
        m_PreviewInstance = Instantiate(m_PreviewInstance, Vector3.zero, Quaternion.identity) as GameObject;
        m_PreviewInstance.transform.localScale = 100 * Vector3.one;
        // 遞歸設(shè)置隱藏標(biāo)志和層
        InitInstantiatedPreviewRecursive(m_PreviewInstance);
        // 關(guān)閉對象渲染
        SetEnabledRecursive(m_PreviewInstance, false);

        m_PreviewBounds = new Bounds(m_PreviewInstance.transform.position, Vector3.zero);
        GetRenderableBoundsRecurse(ref m_PreviewBounds, m_PreviewInstance);
        AddSingleGO(m_PreviewInstance);
    }

    public static void GetRenderableBoundsRecurse(ref Bounds bounds, GameObject go)
    {
        MeshRenderer meshRenderer = go.GetComponent(typeof(MeshRenderer)) as MeshRenderer;
        MeshFilter meshFilter = go.GetComponent(typeof(MeshFilter)) as MeshFilter;
        if (meshRenderer && meshFilter && meshFilter.sharedMesh)
        {
            if (bounds.extents == Vector3.zero)
            {
                bounds = meshRenderer.bounds;
            }
            else
            {
                // 擴(kuò)展包圍盒，以讓包圍盒能夠包含另一個包圍盒
                bounds.Encapsulate(meshRenderer.bounds);
            }
        }
        SkinnedMeshRenderer skinnedMeshRenderer = go.GetComponent(typeof(SkinnedMeshRenderer)) as SkinnedMeshRenderer;
        if (skinnedMeshRenderer && skinnedMeshRenderer.sharedMesh)
        {
            if (bounds.extents == Vector3.zero)
            {
                bounds = skinnedMeshRenderer.bounds;
            }
            else
            {
                bounds.Encapsulate(skinnedMeshRenderer.bounds);
            }
        }
        foreach (Transform transform in go.transform)
        {
            GetRenderableBoundsRecurse(ref bounds, transform.gameObject);
        }
    }

    public static Vector2 Drag2D(Vector2 scrollPosition, Rect position)
    {
        int controlID = GUIUtility.GetControlID("Slider".GetHashCode(), FocusType.Passive);
        Event current = Event.current;
        switch (current.GetTypeForControl(controlID))
        {
            case EventType.MouseDown:
                if (position.Contains(current.mousePosition) && position.width > 50f)
                {
                    GUIUtility.hotControl = controlID;
                    current.Use();
                    // 讓鼠標(biāo)可以拖動到屏幕外后，從另一邊出來
                    EditorGUIUtility.SetWantsMouseJumping(1);
                }
                break;
            case EventType.MouseUp:
                if (GUIUtility.hotControl == controlID)
                {
                    GUIUtility.hotControl = 0;
                }
                EditorGUIUtility.SetWantsMouseJumping(0);
                break;
            case EventType.MouseDrag:
                if (GUIUtility.hotControl == controlID)
                {
                    // 按住 Shift 鍵后，可以加快旋轉(zhuǎn)
                    scrollPosition -= current.delta * (float)((!current.shift) ? 1 : 3) / Mathf.Min(position.width, position.height) * 140f;
                    scrollPosition.y = Mathf.Clamp(scrollPosition.y, -90f, 90f);
                    current.Use();
                    GUI.changed = true;
                }
                break;
        }
        return scrollPosition;
    }


    // 預(yù)覽攝像機(jī)的繪制層 Camera.PreviewCullingLayer
    // 為了防止引擎更改，可以通過反射獲取，這里直接寫值
    private const int kPreviewCullingLayer = 31;

    private static void InitInstantiatedPreviewRecursive(GameObject go)
    {
        go.hideFlags = HideFlags.HideAndDontSave;
        go.layer = kPreviewCullingLayer;
        foreach (Transform transform in go.transform)
        {
            InitInstantiatedPreviewRecursive(transform.gameObject);
        }
    }

    public static void SetEnabledRecursive(GameObject go, bool enabled)
    {
        Renderer[] componentsInChildren = go.GetComponentsInChildren<Renderer>();
        for (int i = 0; i < componentsInChildren.Length; i++)
        {
            Renderer renderer = componentsInChildren[i];
            renderer.enabled = enabled;
        }
    }
}

using UnityEngine;
using UnityEditor;

public class PreviewExampleWindow : EditorWindow
{
    private Editor m_Editor;

    [MenuItem("Window/PreviewExample")]
    static void ShowWindow()
    {
        GetWindow<PreviewExampleWindow>("PreviewExample");
    }

    private void OnDestroy()
    {
        if (m_Editor != null)
        {
            DestroyImmediate(m_Editor);
        }
        m_Editor = null;
    }

    void OnGUI()
    {
        if (m_Editor == null)
        {
            // 第一個參數(shù)這里暫時沒關(guān)系，因?yàn)榫庉嬈鳑]有取目標(biāo)對象
            m_Editor = Editor.CreateEditor(this, typeof(PreviewExampleInspector));
        }

        m_Editor.DrawPreview(GUILayoutUtility.GetRect(300, 200));
    }
}

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