2 from __future__ import print_function
5 from numpy import cos, sin
8 from moedebug import dbg
11 from math import atan2
15 def augment(v): return np.append(v, 1)
16 def augment0(v): return np.append(v, 0)
17 def unaugment(v): return v[0:3]
19 def matmultiply(mat,vect):
21 # we would prefer to write mat @ vect
22 # but that doesn't work in Python 2
23 return np.array((vect * np.matrix(mat).T))[0,:]
25 def augmatmultiply(mat,unaugvect):
26 return unaugment(matmultiply(mat, augment(unaugvect)))
28 findcurve_subproc = None
30 class HelixishCurve():
36 dp = unit_v(cp[1]-cp[0])
37 dq = unit_v(cp[3]-cp[2])
39 dbg('HelixishCurve __init__', cp)
42 # - solve in the plane containing dP and dQ
43 # - total distance normal to that plane gives mu
44 # - now resulting curve is not parallel to dP at P
45 # nor dQ at Q, so tilt it
46 # - [[ pick as the hinge point the half of the curve
47 # with the larger s or t ]] not yet implemented
48 # - increase the other distance {t,s} by a bodge factor
49 # approx distance between {Q,P} and {Q,P}' due to hinging
50 # but minimum is 10% of (wlog) {s,t} [[ not quite like this ]]
52 dPQplane_normal = np.cross(dp, dq)
53 if (np.linalg.norm(dPQplane_normal) < 1E6):
54 dPQplane_normal += [0, 0, 1E5]
55 dPQplane_normal = unit_v(dPQplane_normal)
57 dPQplane_basis = np.column_stack((np.cross(dp, dPQplane_normal),
62 dPQplane_basis = np.vstack((dPQplane_basis, [0,0,0,1]))
64 dPQplane_into = np.linalg.inv(dPQplane_basis)
66 dp_plane = augmatmultiply(dPQplane_into, dp)
67 dq_plane = augmatmultiply(dPQplane_into, dq)
68 q_plane = augmatmultiply(dPQplane_into, q)
69 dist_pq_plane = np.linalg.norm(q_plane)
71 # two circular arcs of equal maximum possible radius
72 # algorithm courtesy of Simon Tatham (`Railway problem',
73 # pers.comm. to ijackson@chiark 23.1.2004)
74 railway_angleoffset = atan2(*q_plane[0:2])
75 railway_theta = tau/4 - railway_angleoffset
76 railway_phi = atan2(*dq_plane[0:2]) - railway_angleoffset
77 railway_cos_theta = cos(railway_theta)
78 railway_cos_phi = cos(railway_phi)
79 if railway_cos_theta**2 + railway_cos_phi**2 > 1E6:
80 railway_roots = np.roots([
81 2 * (1 + cos(railway_theta - railway_phi)),
82 2 * (railway_cos_theta - railway_cos_phi),
85 for railway_r in railway_roots:
86 def railway_CPQ(pq, dpq):
88 return pq + railway_r * [-dpq[1], dpq[0]]
90 railway_CP = railway_CPQ([0,0,0], dp_plane)
91 railway_QP = railway_CPQ(q_plane[0:2], -dq_plane)
92 railway_midpt = 0.5 * (railway_CP + railway_QP)
95 def railway_ST(C, start, end):
97 delta = atan2(*(end - C)[0:2]) - atan2(start - C)[0:2]
100 try_s = railway_ST(railway_CP, [0,0], midpt)
101 try_t = railway_ST(railway_CP, midpt, q_plane)
102 try_st = try_s + try_t
103 if best_st is None or try_st < best_st:
108 start_mu = q_plane[2] / (start_s + start_t)
110 else: # twoarcs algorithm is not well defined
112 start_s = dist_pq_plane * .65
113 start_t = dist_pq_plane * .35
116 bodge = max( q_plane[2] * mu,
117 (start_s + start_t) * 0.1 )
118 start_s += 0.5 * bodge
119 start_t += 0.5 * bodge
124 tilt_basis = np.array([
126 0, cos(tilt), -sin(tilt), 0,
127 0, sin(tilt), cos(tilt), 0,
130 findcurve_basis = augmatmultiply(dPQplane_basis, tilt_basis)
131 findcurve_into = np.linalg.inv(findcurve_basis)
133 q_findcurve = unaugment(findcurve_into, augment(q))
134 dq_findcurve = unaugment(findcurve_into, augment0(dq))
136 findcurve_target = np.concatenate(q_findcurve, dq_findcurve)
137 findcurve_start = (sqrt(start_s), sqrt(start_t), start_la,
138 start_mu, start_gamma, start_kappa)
140 findcurve_epsilon = dist_pq_plane * 0.01
142 if findcurve_subproc is None:
143 findcurve_subproc = subprocess.Popen(
146 stdin=subprocess.PIPE,
147 stdout=subprocess.PIPE,
150 restore_signals=True,
151 universal_newlines=True,
154 findcurve_input = np.hstack((findcurve_target,
156 [findcurve_epsilon]))
157 dbg('RUNNING FINDCURVE', *findcurve_input)
158 print(findcurve_subproc.stdin, *findcurve_input)
159 findcurve_subproc.stdin.flush()
162 l = findcurve_subproc.stdout.readline()
168 hc.findcurve_result = l[0:5]
169 hc.func = symbolic.get_python(something)
170 hc.threshold = l[0]**2
171 hc.total_dist = hc.threshold + l[1]**2
173 def point_at_t(hc, normalised_parameter):
174 dist = normalised_parameter * hc.total_dist
175 ours = [p for p in findcurve_result]
176 if dist <= hc.threshold:
180 ours[1] = sqrt(dist - hc.threshold)
181 return hc.func(*ours)