geometry DEF surface NurbsSurface {
          uOrder 4 
          vOrder 3 
          uDimension 7 
          vDimension 3 
          uTessellation 100  ## needed
          vTessellation 60
          controlPoint [ 
       0.3 0 0, 0.5 3.5 0, 2 4 0, 3 4.2 0, 4 2.5 0, 5 0.5 0, 5.5 -5 0,
       0.3 0 0, 0.5 0 0, 2 0 0, 3 0 0, 4 0 0, 5 -2 0, 5.5 -5 0,
       0.3 0 0, 0.5 -3.5 0, 2 -4 0, 3 -4.2 0, 4 -3.0 0, 5 -0.5 0, 5.5 -5 0,
       ]
          }