Nintendo's Virtual Boy (1995) displayed its games in 3D, through a headset with two monochrome red screens. On Recalbox, the Beetle VB core (mednafen_vb) restores that depth in two ways, depending on the hardware you have.
Your games go into /recalbox/share/roms/virtualboy (.vb, .vboy, .bin, .zip, .7z). No BIOS is required.
In both cases the setting lives in the same place: launch a game, open the RetroArch menu with HOTKEY + B, then go into the core options and look for 3D mode.
These are the classic red-and-blue glasses, they cost a couple of euros and work on any screen.
3D mode to anaglyph.If your TV handles 3D (active or passive glasses), you can put its capabilities to use.
3D mode to side by side.Settings > Video > Scaling.Aspect Ratio to Custom, then adjust the picture so it fills the screen.📷 Screenshot to come:
virtualboy-3d-mode.png
To keep the setting without redoing it every session, save it in a RetroArch override for the virtualboy folder.