def triangle_cp_cnstr(n_steps = 10, dx = -1.99):
cp = CreasePattern(n_steps = n_steps)
cp.nodes = [[ 0, 0, 0 ],
[ 1, 0, 0 ],
[ 1, 1, 0]]
cp.crease_lines = [[ 0, 1 ],
[ 1, 2 ],
[ 2, 0 ]]
cp.facets = [[0, 1, 2 ]]
cp.grab_pts = [(0.5,0.5,0),0]
cp.cnstr_lhs = [
[(0, 0, 1.0)],
[(0, 1, 1.0)],
[(0, 2, 1.0)],
[(1, 1, 1.0)],
[(1, 2, 1.0)],
[(2, 2, 1.0)],
]
cp.cnstr_rhs = [0.0, 0.0, 0.0, 0.0, 0.0, dx]
X = np.zeros((cp.n_dofs,), dtype = float)
X[1] = 0.01
print 'T ', cp.grab_pts_L
print 'initial lengths\n', cp.c_lengths
print 'initial vectors\n', cp.c_vectors
print 'initial R\n', cp.get_R(X)
print 'initial dR\n', cp.get_dR(X)
X = cp.solve(X)
print '========== results =============='
print 'solution X\n', X
print 'final positions\n', cp.get_new_nodes(X)
print 'final vectors\n', cp.get_new_vectors(X)
print 'final lengths\n', cp.get_new_lengths(X)
return cp
