Draw on top of a viewer3D object

In an app created with app designer, a panel is the parent of a viewer3D object, and the object displays a mesh. I want the user to be able to "draw" a polygon on the object with mouse click and select a set of vertices.

The problem is that appearently I cannot "draw" anything on top of the viewer3D object; so I can't show the user the lines they draw. Any axes I create will be masked by the viewer3D, even when I set the appropriate ui stacking. What should I do?

Answer 1

[Reza]

I tried a coulpe of ideas to draw on top of the viewer3d object but none work. The only way I can think of is to get an image screenshot of the viewer3d (as discussed in this thread)

frame = getframe(viewer.Parent);

then set the visibility of the viewer3d off, use the captured image instead, and so on.

But this doesn't seem like a convinent method. I would appreciate any suggestions.