#G4----------------------------------------------
beziersurf bs 4 4 \
  0  0 0   5  0 0  10  0 0  15  0 0 \
  0  5 0   5  5 -2  10  5 2  15  5 0 \
  0 10 0   5 10 0  10 10 0  15 10 0 \
  0 15 0   5 15 0  10 15 0  15 15 0 
mkface bs bs
prism p bs 0 0 5
profile pf o 5 5 1 l 2 c 3 90 l 2 d -1 0 l 5
prism pr pf 0 0 20
bfuse f p pr
nexplode f f
depouille result f 0 0 1 f_10 5 0 0 21 0 0 1

checkprops result -s 1076.83