>>272858793
Capacitance. Oculus controllers have capacitance in the buttons, so it can tell where your fingers are when you're touching them. Index has capacitance in all buttons and the grip, and it's much stronger so it can tell where your fingers are even when not in contact, but doesn't always work perfectly. Vive and WMR are far more limited and either have nothing at all, or games may implement a system that attempts to work like Rift, but isn't very natural.