I'm writing a unity editor script which draws a preview scene in the inspector GUI. Basically, I instantiate a prefab with a camera component and move it into a temporary scene. Then I try to draw the scene onto a texture using that camera. My current approach doesn't seem to be working, or maybe there's something wrong in my code. I'd appreciate any help.

Below is some of my code that does the drawing:

[CustomEditor(typeof(NPCSpawnConfig))]
public class NPCSpawnEditor : Editor
{
    enum SupportedAspects
    {
        Aspect4by3 = 1,
        Aspect5by4 = 2,
        Aspect16by10 = 3,
        Aspect16by9 = 4
    };

    Camera _cam = null;
    RenderTexture _rt;
    Texture2D _tex2d;
    Scene _scene;

    // preview variables
    SupportedAspects _aspectChoiceIdx = SupportedAspects.Aspect16by10;
    float _curAspect;
    // world space (orthographicSize)
    float _worldScreenHeight = 5;
    int _renderTextureHeight = 1080;

    float ToFloat(SupportedAspects aspects)
    {
        switch(aspects)
        {
            case SupportedAspects.Aspect16by10:
                return 16 / 10f;
            case SupportedAspects.Aspect16by9:
                return 16 / 9f;
            case SupportedAspects.Aspect4by3:
                return 4 / 3f;
            case SupportedAspects.Aspect5by4:
                return 5 / 4f;
            default:
                throw new ArgumentException();
        }
    }

    void DrawRefScene()
    {
        _rt = new RenderTexture(Mathf.RoundToInt(_curAspect * _renderTextureHeight), _renderTextureHeight, 16);
        _cam.targetTexture = _rt;
        _cam.Render();
        _tex2d = new Texture2D(_rt.width, _rt.height, TextureFormat.RGBA32, false);
        _tex2d.Apply(false);
        Graphics.CopyTexture(_rt, _tex2d);
    }

    Vector2 GetGUIPreviewSize()
    {
        Vector2 camSizeWorld = new Vector2(_worldScreenHeight * _curAspect, _worldScreenHeight);
        float scaleFactor = EditorGUIUtility.currentViewWidth / camSizeWorld.x;
        return new Vector2(EditorGUIUtility.currentViewWidth, scaleFactor * camSizeWorld.y);
    }

    #region Init
    void OnEnable()
    {
        void OpenSceneDelay()
        {
            EditorApplication.delayCall -= OpenSceneDelay;
            DrawRefScene();
        }

        _aspectChoiceIdx = SupportedAspects.Aspect16by10;

        _scene = EditorSceneManager.NewPreviewScene();

        PrefabUtility.LoadPrefabContentsIntoPreviewScene("Assets/Prefabs/Demo/DemoBkg.prefab", _scene);
        _cam = _scene.GetRootGameObjects()[0].GetComponentInChildren<Camera>();

        _curAspect = ToFloat(_aspectChoiceIdx);
        _cam.aspect = _curAspect;
        _cam.orthographicSize = _worldScreenHeight;

        EditorApplication.delayCall  = OpenSceneDelay;
    }

    void OnDisable()
    {
        EditorSceneManager.ClosePreviewScene(_scene);
    }
    #endregion

    void OnCamSettingChange()
    {
        _curAspect = ToFloat(_aspectChoiceIdx);
        _cam.aspect = _curAspect;
        _cam.orthographicSize = _worldScreenHeight;
        DrawRefScene();
    }

    // GUI states
    class GUIControlStates
    {
        public bool foldout = false;
    };
    GUIControlStates _guiStates = new GUIControlStates();
    public override void OnInspectorGUI()
    {
        // draw serializedObject fields
        // ....

        
        // display options
        using (var scope = new EditorGUI.ChangeCheckScope())
        {
            _aspectChoiceIdx = (SupportedAspects)EditorGUILayout.EnumPopup("label", (Enum)_aspectChoiceIdx);
            if (scope.changed)
            {
                OnCamSettingChange();
            }
        }
        _guiStates.foldout = EditorGUILayout.Foldout(_guiStates.foldout, "label", true);
        if(_guiStates.foldout)
        {
            using (var scope = new EditorGUI.ChangeCheckScope())
            {
                _worldScreenHeight = EditorGUILayout.FloatField("label", _worldScreenHeight);
                _renderTextureHeight = EditorGUILayout.IntField("label", _renderTextureHeight);

                if (scope.changed)
                {
                    OnCamSettingChange();
                }
            }
        }

        if (_tex2d != null)
        {
            Vector2 sz = GetGUIPreviewSize();
            Rect r = EditorGUILayout.GetControlRect(false,
                GUILayout.Height(sz.y),
                GUILayout.ExpandHeight(false));
            EditorGUI.DrawPreviewTexture(r, _tex2d);
        }
    }
}

Here is the result: (only clear color is displayed, but the prefab contains a lot of sprites that should be drawn. The camera is also correctly positioned relative to the sprites.)

CodePudding user response：

Solved this by adding the following 2 lines after getting the camera component.

    _cam.cameraType = CameraType.Preview;
    _cam.scene = _scene;