This example looks like contour.tcl example, but it contains 2 set of contours: "lower " set and "upper" set. Upper set of contours is shifted up at 0.2. The resulting surface is between these contours sets.
Pic 1. Surface built from contour inequalities
This result was obtained with "examples/surfit/curvs/contour_ineq.tcl"
script.
surfit: gridding and contouring software.