FIND CLOSEST SURFACE VERTEX TO COORDINATES
   wb_command -surface-closest-vertex
      <surface> - the surface to use
      <coord-list-file> - text file with coordinates
      <vertex-list-out> - output - the output text file with vertex numbers

      For each coordinate XYZ triple, find the closest vertex in the surface,
      and output its vertex number into a text file.  The input file should
      only use whitespace to separate coordinates (spaces, newlines, tabs), for
      instance:

      20 30 25
      30 -20 10