I have a vertex shader where I am trying to have the visibility of some terrain fade out at some distance from the viewpoint. I was trying to ramp the fragment color alpha down from 1.0 to 0.0 to do this. That should work, shouldn't it?

Anyway I notice that even when I explicitly just set the fragment color to 0, the objects are still visible. Shouldn't setting the fragment color w value to 0 make it invisible?