key guid

| Help:
-------
          p, P   : switch to a point-based representation
          w, W   : switch to a wireframe-based representation (where available)
          s, S   : switch to a surface-based representation (where available)

          j, J   : take a .PNG snapshot of the current window view
          c, C   : display current camera/window parameters
          f, F   : fly to point mode

          e, E   : exit the interactor
          q, Q   : stop and call VTK's TerminateApp

           +/-   : increment/decrement overall point size
     +/- [+ ALT] : zoom in/out

          g, G   : display scale grid (on/off)
          u, U   : display lookup table (on/off)

    r, R [+ ALT] : reset camera [to viewpoint = {0, 0, 0} -> center_{x, y, z}]

    ALT + s, S   : turn stereo mode on/off
    ALT + f, F   : switch between maximized window mode and original size

          l, L           : list all available geometric and color handlers for t
he current actor map
    ALT + 0..9 [+ CTRL]  : switch between different geometric handlers (where av
ailable)
          0..9 [+ CTRL]  : switch between different color handlers (where availa
ble)

    SHIFT + left click   : select a point

          x, X   : toggle rubber band selection mode for left mouse button