-tau = np.pi * 2
-
-origin = np.array((0,0,0))
-unit_x = np.array((1,0,0))
-unit_y = np.array((0,1,0))
-unit_z = np.array((0,0,1))
+class DoubleCubicBezier():
+ def __init__(db, cp):
+ single = BezierSegment(cp)
+ midpoint = np.array(single.point_at_t(0.5))
+ mid_dirn = single.point_at_t(0.5 + 0.001) - midpoint
+ mid_dirn /= np.linalg.norm(mid_dirn)
+ ocp_factor = 0.5
+ mid_scale = ocp_factor * 0.5 * (np.linalg.norm(cp[1] - cp[0]) +
+ np.linalg.norm(cp[3] - cp[2]))
+ db.b0 = BezierSegment([ cp[0],
+ cp[1] * ocp_factor + cp[0] * (1-ocp_factor),
+ midpoint - mid_dirn * mid_scale,
+ midpoint ])
+ db.b1 = BezierSegment([ midpoint,
+ midpoint + mid_dirn * mid_scale,
+ cp[2] * ocp_factor + cp[3] * (1-ocp_factor),
+ cp[3] ])
+ def point_at_t(db, t):
+ if t < 0.5:
+ return db.b0.point_at_t(t*2)
+ else:
+ return db.b1.point_at_t(t*2 - 1)