What is the proper way to draw previews for custom assets

I am generating a rotatable preview image for a custom asset. I’ve got it working pretty well, but I’m not sure the method I’m using is advisable. For now it is all consolidated into a single function that returns a Texture2D, and takes as parameters, the asset itself, a Quaternion(orientation) and Vector2(output texture size). This function is then used by the object’s custom inspector’s OnPreviewGUI function.

I’m generating the preview image for the asset, by creating some temporary objects in the scene, on a particular layer. Once of the objects is a camera (culled to that layer), a light(also culled to that layer), and an instance of the asset I want to preview, reference by the appropriate render components. A RenderTexture is created and attached to the camera. Finally, the camera.render function and texture2d .Readpixels function are used to grab the resultant frame.

For now, when the preview generation function is done, the objects are destroyed.

While this works pretty well, and object and preview-render screen draw (almost) properly, I’ve hit a couple of issues.

-One issue is that I’m creating these temporary objects, in whatever happens to be the current scene. So, Lights in the current scene (with cull everything) shine on my preview object. -Also, it’s possible there might be objects in the scene using that particular preview culling layer, that could end up visible in the preview.

To work around this I tried out creating a new scene at runtime using EditorSceneManager.NewScene(NewSceneSetup.EmptyScene,NewSceneMode.Additive).
Then moving the camera, render object, and preview lights, to the new scene with SceneManager.MoveGameObjectToScene (I’m not sure how to create those objects in the preview scene, initially.)

Surprisingly, even after putting all the preview objects in the new scene, THEN doing the camera.render call; the light from the current editor scene continued to shine on my preview object! Unfortunately, the new scene also makes unity’s window title text flicker occasionally, even though I never call SetCurrentScene.

Perhaps I’m on the right track and have some error/omission in the code, or perhaps I’m totally off track, and should be doing this differently.

Any suggestions on how to fix these few issues are appreciated.

Here is the code: I’m excluding the some of object setup stuff, and just leaving the meat. Let me know if you want to see more.

 private Scene previewScene;
 override public Texture2D GenerateSnapshot(Quaternion rotation, Vector2 size, bool hideBackFaces)
 {
     int layerToUse = 8;
     if (size.x < 64) { size.x = 64; size.y = 64; }
     RenderTexture rendTextr = new RenderTexture((int)size.x, (int)size.y, 16, RenderTextureFormat.ARGB32);
     rendTextr.antiAliasing = 8;
     rendTextr.Create();

     RenderTexture currentActiveRT = RenderTexture.active;
     // Set the supplied RenderTexture as the active one
     RenderTexture.active = rendTextr;
     //setup object to render
     
     GameObject edgeRendObject = new GameObject();
     edgeRendObject.layer = layerToUse;
     //  edgeRendObject gets setup here (omitted)

     GameObject camObject = new GameObject();
     Camera cam = camObject.AddComponent<Camera>();
     // cam setup goes here (omitted)
     cam.cameraType = CameraType.Game;//.SceneView;//.Preview;
     cam.cullingMask = 1 << layerToUse;

     GameObject light1 = new GameObject();
     Light l1 = light1.AddComponent<Light>();
     l1.cullingMask = 1 << layerToUse;
     //l1 setup here (omitted)

      Scene currentScene = SceneManager.GetActiveScene();
     if (!previewScene.IsValid())
     {
         previewScene = EditorSceneManager.NewScene(NewSceneSetup.EmptyScene, NewSceneMode.Additive);
         SceneManager.SetActiveScene(currentScene);
     }

     SceneManager.MoveGameObjectToScene(camObject, previewScene);
     SceneManager.MoveGameObjectToScene(edgeRendObject, previewScene);
     SceneManager.MoveGameObjectToScene(light1, previewScene);

     RenderTexture.active = rendTextr;
     cam.Render();
     Texture2D outputTexture = new Texture2D((int)size.x, (int)size.y, TextureFormat.RGB24, false);
     outputTexture.ReadPixels(new Rect(0, 0, size.x, size.y), 0, 0);
     outputTexture.Apply();

     RenderTexture.active = currentActiveRT;

     Object.DestroyImmediate(camObject);
     Object.DestroyImmediate(edgeRendObject);
     Object.DestroyImmediate(light1);
     DestroyImmediate(rendTextr);

     SceneManager.SetActiveScene(currentScene);
     EditorSceneManager.CloseScene(previewScene, true);

     return outputTexture;

}