From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Wed, 29 Nov 2017 17:40:07 +0000 (+0000)
Subject: helixish: fixes
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?a=commitdiff_plain;h=697b8aae30f01ace7a87fb6fcc1c23faecb14c1f;p=moebius3.git

helixish: fixes

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

diff --git a/helixish.py b/helixish.py
index d0f99b6..14df461 100644
--- a/helixish.py
+++ b/helixish.py
@@ -59,9 +59,14 @@ class HelixishCurve():
     #     but minimum is 10% of (wlog) {s,t} [[ not quite like this ]]
 
     dPQplane_normal = np.cross(dp, dq)
-    if (np.linalg.norm(dPQplane_normal) < 1E6):
+
+    if np.linalg.norm(dPQplane_normal) < 1E-6:
       dbg('dPQplane_normal small')
-      dPQplane_normal += [0, 0, 1E5]
+      dPQplane_normal = np.cross([1,0,0], dp)
+    if np.linalg.norm(dPQplane_normal) < 1E-6:
+      dbg('dPQplane_normal small again')
+      dPQplane_normal = np.cross([0,1,0], dp)
+
     dPQplane_normal = unit_v(dPQplane_normal)
 
     dPQplane_basis = np.column_stack((np.cross(dp, dPQplane_normal),