I have created a 3D scene with a viewport containing a GUI Control with some labels (to have 2D text floating in 3D world like a billboard). It shows perfectly in its own 3D Scene.
In my larger 3D world scene I instance the billboard and it shows up in the world and works and the labels show correctly.
However, when I run the game, the viewport is totally black.
Would be grateful for any suggestions on what the problem might be. I think it might be something to do with the camera in the 3D world.