polyline p 0 0 0 4 0 0 4 0 3 3 0 3 2 0 1 1 0 3 0 0 3 0 0 0
mkplane f p
prism s f 0 1 0
donly s

OFFSETSHAPE 3 {} $calcul $type

checkprops result -v 630

checknbshapes result -shell 1
