struct
let skel =
[| [| false ; false ; true ; false |] ;
[| false ; false ; true ; false |] ;
[| true ; true ; false ; true |] ;
[| false ; false ; true ; false |] |]
let pos = [| -1.,0.,-0.5 ; 1.,0.,0. ; 0.,1.,0. ; 0.,2.,0.|]
let root = 1
let all = skel, pos, root
let first = 0
end