chiark / gitweb /
helixish: remember to transform back from findcurve basis (!)
[moebius3.git] / helixish.py
index 1d36faecef8e4b55501b8384259b589cced9e980..27485eac5e965293e7311976f39466fef807ca08 100644 (file)
@@ -72,27 +72,19 @@ class HelixishCurve():
     dp_plane = augmatmultiply(dPQplane_into, dp, augwith=0)
     dq_plane = augmatmultiply(dPQplane_into, dq, augwith=0)
     q_plane  = augmatmultiply(dPQplane_into, q)
-    dist_pq_plane = np.linalg.norm(q_plane)
+    dist_pq_plane = np.linalg.norm(q_plane[0:2])
 
     vdbg_plane = MatrixVisdebug(vdbg(), dPQplane_basis)
 
-    dbg('plane p', p_plane_check, 'dp', dp_plane, 'dq', dq_plane, 'q', q_plane)
+    dbg('plane p', p_plane_check, 'dp', dp_plane, 'dq', dq_plane,
+        'q', q_plane, 'dist_pq_plane', dist_pq_plane)
     vdbg_plane.arrow(p_plane_check, dp_plane)
     vdbg_plane.arrow(q_plane,       dq_plane)
 
-    # two circular arcs of equal maximum possible radius
-    # algorithm courtesy of Simon Tatham (`Railway problem',
-    # pers.comm. to ijackson@chiark 23.1.2004)
-    railway_angleoffset = atan2(*q_plane[0:2])
-    railway_theta = atan2(*dp_plane[0:2]) - railway_angleoffset
-    railway_phi   = atan2(*dq_plane[0:2]) - railway_angleoffset
-    railway_cos_theta = cos(railway_theta)
-    railway_cos_phi   = cos(railway_phi)
-
     railway_inplane_basis_x = np.hstack((q_plane[0:2], [0]))
     railway_inplane_basis = np.column_stack((
       railway_inplane_basis_x,
-      np.cross([0,0,1], railway_inplane_basis_x),
+      -np.cross([0,0,1], railway_inplane_basis_x),
       [0,0,1],
       [0,0,0],
     ))
@@ -103,20 +95,62 @@ class HelixishCurve():
     railway_basis = matmatmultiply(dPQplane_basis, railway_inplane_basis)
     dbg('railway_basis\n', railway_basis)
     vdbg().basis(railway_basis, hue=(1,0,1))
+    vdbg_railway = MatrixVisdebug(vdbg(), railway_basis)
+
+    # two circular arcs of equal maximum possible radius
+    # algorithm courtesy of Simon Tatham (`Railway problem',
+    # pers.comm. to ijackson@chiark 23.1.2004)
+    railway_angleoffset = atan2(*q_plane[0:2])
+    # these two angles are unconventional: clockwise from north
+    railway_theta = tau/4 - (atan2(*dp_plane[0:2]) - railway_angleoffset)
+    railway_phi   = tau/4 - (atan2(*-dq_plane[0:2]) - railway_angleoffset)
+    railway_cos_theta = cos(railway_theta)
+    railway_cos_phi   = cos(railway_phi)
+
     dbg('railway:', railway_theta, railway_phi, railway_angleoffset)
 
+    def vdbg_railway_angle(start, angle, **kw):
+      vdbg_railway.arrow(start, [sin(angle), cos(angle), 0], **kw)
+    vdbg_railway_angle([0, 0, 0.1], railway_theta, color=(1, 0.5, 0))
+    vdbg_railway_angle([1, 0, 0.1], railway_phi,   color=(1, 0.5, 0))
+    vdbg_railway_angle([1, 0, 0.1], 0,             color=(1, 1.00, 0))
+    vdbg_railway_angle([1, 0, 0.1], tau/4,         color=(1, 0.75, 0))
+
     if railway_cos_theta**2 + railway_cos_phi**2 > 1E-6:
-      railway_roots = np.roots([
+      railway_polynomial = [
         2 * (1 + cos(railway_theta - railway_phi)),
         2 * (railway_cos_theta - railway_cos_phi),
-        -1
-        ])
-      for railway_r in railway_roots:
-        dbg(' twoarcs root r=',railway_r)
+        -1,
+        ]
+      railway_roots = np.roots(railway_polynomial)
+      dbg('railway poly, roots:', railway_polynomial, railway_roots)
+
+      #vdbg_railway.circle([0,0,0], [0,0, dist_pq_plane], color=(.5,0,0))
+      #vdbg_railway.circle([1,0,0], [0,0, 0.05], color=(.5,0,0))
+      #vdbg().circle(p, dPQplane_normal * dist_pq_plane, color=(.5,.5,0))
+
+      for railway_r_pq1 in railway_roots:
+        # roots for r are calculated based on coordinates where
+        # Q is at (1,0) but our PQ distance is different
+        railway_r = railway_r_pq1 * dist_pq_plane
+        dbg(' twoarcs root r_pq1=', railway_r_pq1, 'r=',railway_r,
+            railway_polynomial[0] * railway_r_pq1 * railway_r_pq1 +
+            railway_polynomial[1] * railway_r_pq1                 +
+            railway_polynomial[2]
+        )
+
+        vdbg_railway.circle([0,0,0], [0,0, railway_r], color=(1,0,0))
+        #vdbg().circle(p, dPQplane_normal * railway_r, color=(1,1,0))
 
         def railway_CPQ(pq, dpq, railway_r):
           CPQ = pq + railway_r * np.array([-dpq[1], dpq[0]])
           dbg('railway_CPQ', railway_r, pq, dpq, CPQ)
+          vdbg_plane.circle( np.hstack((CPQ, [0])),
+                             [0, 0, railway_r],
+                             color = (1,1,1) )
+          #vdbg_plane.circle( np.hstack(( 2*np.asarray(pq) - CPQ, [0])),
+          #                   [0, 0, railway_r],
+          #                   color = (.5,.5,.5) )
           return CPQ
 
         railway_CP = railway_CPQ([0,0],         dp_plane, railway_r)
@@ -126,15 +160,15 @@ class HelixishCurve():
         best_st = None
         def railway_ST(C, start, end, railway_r):
           delta = atan2(*(end - C)[0:2]) - atan2(*(start - C)[0:2])
+          dbg('railway_ST C', C, 'start', start, 'end', end, 'delta', delta)
+          if delta < 0: delta += tau
           s = delta * railway_r
-          dbg('railway_ST', C, start, end, railway_r, s)
+          dbg('railway_ST delta', delta, 'r', railway_r, 's', s)
           return s
 
         try_s = railway_ST(railway_CP, [0,0], railway_midpt, railway_r)
         try_t = railway_ST(railway_CP, railway_midpt, q_plane[0:2], railway_r)
         dbg('try_s, _t', try_s, try_t)
-        if try_s < 0 or try_t < 0:
-          continue
 
         try_st = try_s + try_t
         if best_st is None or try_st < best_st:
@@ -218,6 +252,7 @@ class HelixishCurve():
     findcurve_subproc.stdin.flush()
 
     hc.func = symbolic.get_python()
+    hc.findcurve_basis = findcurve_basis
     commentary = ''
 
     while True:
@@ -253,4 +288,5 @@ class HelixishCurve():
       ours[1] = sqrt(dist - hc.threshold)
     asmat = hc.func(*ours)
     p = asmat[:,0]
+    p = augmatmultiply(hc.findcurve_basis, p)
     return p