http://img230.imageshack.us/f/quake1blender249.png/
*add mesh plane (spacebar)
*subdivide multi 3 (W menu)
*scale 0.8 (S+0.8)
*tringulate (ctrl+T)
*flip some triangle edges (ctrl+F menu)
*move some vertices (on 0.1 blenderunit grid)
*split everything (select face press Y)
*extrude (E region) + right click
*move created faces along the z axis (G+Z)
*Select connected vertices (L)
*seperate created brushes (P)
*select everything
*export to quake3.map scale =80 (0.1 blender -> 8 quake units)
*open with gedit (or your prefered text editor)
*replace "0 0 0 1 1 0 0 0" with "0 0 0 1 1"
finished
alltogether 5 minutes, perfect terrain on gird :)
I tried to record it with gtk-recordmydesktop but unfortunately it failed to record the opengl windows XD