plane pl 0 0 0 1 1 1
pcone con pl 2 1 3 60
explode con w
nurbsconvert w con_1
cone con 0.1 .1 .1 1 1 1 -17 1.9
getanasurf res w con 1.e-3 con
if {[isdraw res]} {
  set log [dump res]
  if { [regexp {ConicalSurface} $log ] != 1 } {
     puts "Error: surface is not a conical surface"
  }
} else {
  puts "Error: required surface is not got"
}