helixish: fix sign problems

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

diff --git a/helixish.py b/helixish.py
index 27485eac5e965293e7311976f39466fef807ca08..171fe3bdc8866608339e6cf887e9027cc9d2a864 100644 (file)
--- a/helixish.py
+++ b/helixish.py
@@ -154,8 +154,8 @@ class HelixishCurve():
           return CPQ
 
         railway_CP = railway_CPQ([0,0],         dp_plane, railway_r)
-        railway_QP = railway_CPQ(q_plane[0:2], -dq_plane, railway_r)
-        railway_midpt = 0.5 * (railway_CP + railway_QP)
+        railway_CQ = railway_CPQ(q_plane[0:2], -dq_plane, railway_r)
+        railway_midpt = 0.5 * (railway_CP + railway_CQ)
 
         best_st = None
         def railway_ST(C, start, end, railway_r):
@@ -166,13 +166,13 @@ class HelixishCurve():
           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)
+        try_s = railway_ST(railway_CP, railway_midpt, [0,0], railway_r)
+        try_t = railway_ST(railway_CQ, railway_midpt, q_plane[0:2], railway_r)
         dbg('try_s, _t', try_s, try_t)
 
         try_st = try_s + try_t
         if best_st is None or try_st < best_st:
-          start_la = 1/railway_r
+          start_la = -1/railway_r
           start_s = try_s
           start_t = try_t
           best_st = try_st