15.36  FILL 

FILL BY={nset|"name"} [LEVEL=n] [ADD=[n|Z]]
     [LIMITED [VLOG[=ON|OFF]] [[FROM]|TO [[X=]nx,[[Y=]ny[,[Z=]nz]]]
          [RECURSOR] [CURSOR] ]
     [POINTS|COLUMNS=[FROM] n1 [TO] [n2]]
     [LINES|ROWS=[FROM] n1 [TO] [n2]]
     [SETS=[FROM] n1 [TO] [n2]]
     [SELECT="name"]
This  takes  the data set nset and assumes it is a closed curve.  It fills
the curve by adding 1 to each Z value of the specified data sets which lie
inside the curve.  For mesh data Z must be the dependent variable.

If  the  filled  data  set  has  finite  DX  then it is incremented by the
fraction of the curve that lies within the DX of X.

If  you specify LEVEL=n and DY is finite then n steps are used to find the
part of the curve that lies within each channel +-DY.