From 659f23b40638b4db9bd2a9a49b092c4c4e584a8a Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Sat, 4 Nov 2017 22:00:45 +0000
Subject: [PATCH] Twirler; add extra_zeta

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---
 moebius.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/moebius.py b/moebius.py
index 944ea9b..3b7ad46 100644
--- a/moebius.py
+++ b/moebius.py
@@ -42,8 +42,8 @@ class Twirler(ParametricCircle):
     tw._cycles = cycles
     tw._begin_zeta = begin_zeta
     tw._axis = np.cross(r0, r1)
-  def dirn(tw, theta):
-    zeta = tw._begin_zeta + theta * tw._cycles
+  def dirn(tw, theta, extra_zeta=0):
+    zeta = tw._begin_zeta + theta * tw._cycles + extra_zeta
     r = tw.radius(theta)
     return cos(zeta) * r + sin(zeta) * tw._axis
 
-- 
2.30.2