When I display geometry as a 3D overlay on a surface (grouped), it isn’t visible in the top view. As soon as I move the view away from the top view, everything displays normally.
Is there anything specific I need to take into account if I want to display overlays in the top view?
Perhaps draw the overlay a smidgen above the face?
Thanks for the suggestion. I’ve already tried that. Currently, the geometry is 0.3 mm above the surface. Unfortunately, that didn’t make any difference. Although I think that should actually be pretty irrelevant, since the geometry itself is already several centimeters high.
I tested the overlay function on its own with simple lines, and the display works fine in the top view. And here I can also lift the plane and see how it covers the overlay. So maybe the problem lies more in how the overlay geometry is generated. I’m not sure; I’ll look into it further. I thought it might be a known issue.
Check the official Issue tracker:
Thanks for the hint, very interesting.
I’ve now been able to resolve the overlay issue by adding an additional 2D overlay on in top view and significantly larger bounds. 
2D drawing in screen space is not limited by the extents. The API docs explicitly state this.
If you feel the 3D drawing in parallel projection is a bug, please log an issue in the tracker.