In the Source/SteamVR version of the problem, if I take off the headset and look carefully into its screen, I’ll see there are actually 3 pictures there; they’re positioned precisely right, so when I have the headset on, I see two (the middle one overlaps with the left for the left eye and the right for the right eye). I’s a little funny actually :-) I guess vorpX and SteamVR are both “stereoscoping” the image in turns