I tested with my passive monitor too. Many games works (dirt2, etc), but in FPV freerider nothing happens when i press the shortcut ctrl+t.
Why? It should be ok by default: "for most 3D games based on Unity, without needing any plugin"
So maybe something is disabled or set what stereo don't like? Can you check please?
You only need the free 3d vision driver and a cheap anaglyph paperglasses.
thank you in advance!!
ps: " you don't need to do anything in unity to get it to work. You merely compile the game, make sure that 3d vision is enabled in the control panel, then start the game in fullscreen. 3d vision should automatically start making the game 3d"
from here