From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Sat, 30 Dec 2017 12:30:18 +0000 (+0000)
Subject: helixish: make railway basis right-handed
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ian/git?a=commitdiff_plain;h=b72f43d62a157dd90bedb96d79b927f5c2483048;p=moebius3.git

helixish: make railway basis right-handed

Previously the y axis was reversed!

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

diff --git a/helixish.py b/helixish.py
index 88769c3..0235e5b 100644
--- a/helixish.py
+++ b/helixish.py
@@ -83,7 +83,7 @@ class HelixishCurve():
     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],
     ))