def taut_rays(tri, angle):
# get the extreme rays of the taut cone - note that the returned
# vectors are non-negative because they "point up"
N = edge_equation_matrix_taut(tri, angle)
N = Matrix(N)
dim = N.dimensions()[1]
elem_ieqs = [[0] + list(elem_vector(i, dim)) for i in range(dim)]
N_rows = [v.list() for v in N.rows()]
N_eqns = [[0] + v for v in N_rows]
P = Polyhedron(ieqs = elem_ieqs, eqns = N_eqns)
rays = [ray.vector() for ray in P.rays()]
for ray in rays:
assert all(a.is_integer() for a in ray)
# all of the entries are integers, represented in QQ, so we clean them.
return [vector(ZZ(a) for a in ray) for ray in rays]
