set view equal xyz
  set ticslevel 0
  set colors classic

  set xlabel 'x'
  set ylabel 'y'
  set zlabel 'z'

  r = 130
  set xrange [-r:r]
  set yrange [-r:r]
  set zrange [-r:r]

  set hidden3d
  splot \
    'grid.txt' u 3:4:($2==4?$5:NaN) w d lt 1 t 'bulge', \
    'grid.txt' u 3:4:($2==3?$5:NaN) w d lt 3 t 'disk'

  pause -1 'Press Enter to continue: '