HUD { children SwingingArm { translation 2 0.5 -2 children  [
          Transform {
              scale 0.2 0.2 0.2
              children [
                  Shape {
                      appearance Appearance { 
                          material Material {transparency 0.5 }
                          texture ImageTexture { url "disc.gif"  }
                      }
                      geometry IndexedFaceSet {
                          solid FALSE
                          coord Coordinate { point [ -1.0  -1.0  0.0,
                                                      1.0  -1.0  0.0,
                                                      1.0   1.0  0.0,
                                                     -1.0   1.0  0.0] }
                          texCoord TextureCoordinate { point [ 0 1,
                                                               1 1,
                                                               1 0,
                                                               0 0 ] }
                          coordIndex    [ 0, 1, 2, 3, -1]
                          texCoordIndex [ 3, 2, 1, 0, -1]
                      }
                  }
                  Group { children [
                  DEF CONTROL_TRANS Transform {
                      translation 0 0 0
                      children DEF CONTROL Sphere { radius 0.1 }
                  }
                  DEF DRAGSENSOR PlaneSensor {
                      minPosition -1 -1 
                      maxPosition  1  1
                  }
                  ] }
              ]
          }