helixish: fix tilt sense

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

diff --git a/helixish.py b/helixish.py
index dde107d1efa5d20d7a16750d37d95317d2444118..a4519a2614ff3baceea2434f46d4effb8317638d 100644 (file)
--- a/helixish.py
+++ b/helixish.py
@@ -142,8 +142,8 @@ class HelixishCurve():
     tilt = atan(start_mu)
     tilt_basis = np.array([
       [ 1,     0,           0,         0 ],
-      [ 0,   cos(tilt), -sin(tilt),    0 ],
-      [ 0,   sin(tilt),  cos(tilt),    0 ],
+      [ 0,   cos(tilt),  sin(tilt),    0 ],
+      [ 0,  -sin(tilt),  cos(tilt),    0 ],
       [ 0,     0,           0,         1 ],
     ])
     findcurve_basis = matmatmultiply(dPQplane_basis, tilt_basis)