# v as a function of the position x,y,z on a surface
      x       y       z         v
     0.0    -0.5     5.5       1.1
     0.0     0.0     4.4       0.2
     0.0     0.5     5.5       1.1
                             
     0.5    -0.5     5.2       0.1
     0.5     0.0     4.2       1.4
     0.5     0.5     5.2       0.1
                             
     1.0    -0.5     4.5       0.0
     1.0     0.0     4.0       1.8
     1.0     0.5     4.5       0.0
                             
     1.3    -0.5     3.8       0.2
     1.5     0.0     3.8       0.7
     1.3     0.5     3.8       0.2
