polyline p 0 0 0 10 0 0 10 0 7 6 0 7 6 0 3 5 0 5 0 0 5 0 0 0
mkplane f p
prism s f 0 10 0

set distance 1
offsetparameter 1.e-7 $calcul $type
offsetload s $distance
offsetperform result

checkprops result -v 1152

checknbshapes result -shell 1
