2 from __future__ import print_function
5 from numpy import cos, sin
8 from moebdebug import dbg
10 def augment(v): return np.append(v, 1)
11 def augment0(v): return np.append(v, 0)
12 def unaugment(v): return v[0:3]
14 findcurve_subproc = None
16 class HelixishCurve():
20 dp = unit_v(cp[1]-cp[0])
21 dq = unit_v(cp[3]-cp[2])
23 dbg('HelixishCurve __init__', cp)
26 # - solve in the plane containing dP and dQ
27 # - total distance normal to that plane gives mu
28 # - now resulting curve is not parallel to dP at P
29 # nor dQ at Q, so tilt it
30 # - [[ pick as the hinge point the half of the curve
31 # with the larger s or t ]] not yet implemented
32 # - increase the other distance {t,s} by a bodge factor
33 # approx distance between {Q,P} and {Q,P}' due to hinging
34 # but minimum is 10% of (wlog) {s,t} [[ not quite like this ]]
36 dPQplane_normal = np.cross(dp, dq)
37 if (np.norm(dPQplane_normal) < 1E6):
38 dPQplane_normal += [0, 0, 1E5]
39 dPQplane_normal = unit_v(dPQplane_normal)
41 dPQplane_basis = np.column_stack(np.cross(dp, dPQplane_normal),
45 dPQplane_basis = np.vstack(dPQplane_basis, [0,0,0,1])
46 dPQplane_into = np.linalg.inv(dPQplane_basis)
48 dp_plane = unaugment(dPQplane_into * augment0(dp))
49 dq_plane = unaugment(dPQplane_into * augment0(dq))
50 q_plane = unaugment(dPQplane_into * augment(q))
51 dist_pq_plane = np.linalg.norm(q_plane)
53 # two circular arcs of equal maximum possible radius
54 # algorithm courtesy of Simon Tatham (`Railway problem',
55 # pers.comm. to ijackson@chiark 23.1.2004)
56 railway_angleoffset = atan2(*q_plane[0:1])
57 railway_theta = tau/4 - railway_angleoffset
58 railway_phi = atan2(*dq_plane[0:1]) - railway_angleoffset
59 railway_cos_theta = cos(railway_theta)
60 railway_cos_phi = cos(railway_phi)
61 if railway_cos_theta**2 + railway_cos_phi**2 > 1E6:
62 railway_roots = np.roots([
63 2 * (1 + cos(railway_theta - railway_phi)),
64 2 * (railway_cos_theta - railway_cos_phi),
67 for railway_r in railway_roots:
68 def railway_CPQ(pq, dpq):
70 return pq + railway_r * [-dpq[1], dpq[0]]
72 railway_CP = railway_CPQ([0,0,0], dp_plane)
73 railway_QP = railway_CPQ(q_plane[0:2], -dq_plane)
74 railway_midpt = 0.5 * (railway_CP + railway_QP)
77 def railway_ST(C, start, end):
79 delta = atan2(*(end - C)[0:2]) - atan2(start - C)[0:2]
82 try_s = railway_ST(railway_CP, [0,0], midpt)
83 try_t = railway_ST(railway_CP, midpt, q_plane)
84 try_st = try_s + try_t
85 if best_st is None or try_st < best_st:
90 start_mu = q_plane[2] / (start_s + start_t)
92 else: # twoarcs algorithm is not well defined
94 start_s = dist_pq_plane * .65
95 start_t = dist_pq_plane * .35
98 bodge = max( q_plane[2] * mu,
99 (start_s + start_t) * 0.1 )
100 start_s += 0.5 * bodge
101 start_t += 0.5 * bodge
106 tilt_basis = np.array([
108 0, cos(tilt), -sin(tilt), 0,
109 0, sin(tilt), cos(tilt), 0,
112 findcurve_basis = dPQplane_basis * tilt_basis
113 findcurve_into = np.linalg.inv(findcurve_basis)
115 q_findcurve = unaugment(findcurve_into, augment(q))
116 dq_findcurve = unaugment(findcurve_into, augment0(dq))
118 findcurve_target = np.concatenate(q_findcurve, dq_findcurve)
119 findcurve_start = (sqrt(start_s), sqrt(start_t), start_la,
120 start_mu, start_gamma, start_kappa)
122 findcurve_epsilon = dist_pq_plane * 0.01
124 if findcurve_subproc is None:
125 findcurve_subproc = subprocess.Popen(
128 stdin=subprocess.PIPE,
129 stdout=subprocess.PIPE,
132 restore_signals=True,
133 universal_newlines=True,
136 findcurve_input = np.hstack((findcurve_target,
138 [findcurve_epsilon])))
139 dbg('RUNNING FINDCURVE', *findcurve_input)
140 print(findcurve_subproc.stdin, *findcurve_input)
141 findcurve_subproc.stdin.flush()
144 l = findcurve_subproc.stdout.readline()
149 findcurve_result = l[0:5]