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vars,funct (left-click): read surface
  set readsurf2flag <0,1>
  set insurf <surface:tri/quad>
  read_binary_surf
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Read binary surface (quads or triangles) in entry
to left to either primary or secondary surface,
depending on whether the adjoining "2" is ticked.

If a previous primary or secondard surface has
already been read, it is replaced.
