If a game has Geometry 3D everything is rendered twice using two cameras exactly like in native VR apps. This is ‘real’ 3D. If you think it’s not enough and want to enhance the effect, you can do that by raising the “3D-Strength/Separation” parameter on the main page of the ingame menu. Be careful though, the default value usually is close to a natural 3D strength. You can go way beyond that, but doing so makes the world look smaller.
Just in case: also make sure to raise the field of view. Things looking wrong may be a result of skipping this (very important!) step. The general options you have in this regard are described in the Essential Hints Guide in the help.