mrdoob/three.js — pull request #2043 by mrspeaker (2012-06-08 10:44:49+00:00)
Title: Make the noFly param in FirstPersonControls work by constraining the Y axis

I needed this for my game, so the FPS controller didn't fly above/below the ground. There was already a noFly parameter, but it wasn't used. My (perhaps naive) solution was to store the original camera position and reset the Y at the end of the update function.