Tweak shell spin

src/Geometry/Vector.hs

@@ -133,6 +133,17 @@ normalizeAngle f
     floor' :: Float -> Float
     floor' x = fromIntegral (floor x :: Int)
 
+-- | Normalize an angle to be between -pi and pi radians
+nearZeroAngle :: Float -> Float
+{-# INLINE nearZeroAngle  #-}
+nearZeroAngle a
+    | a >= -pi && a < pi = a
+    | otherwise = a - 2 * pi * floor' ((a +pi) / (2 * pi))
+  where
+    floor' :: Float -> Float
+    floor' x = fromIntegral (floor x :: Int)
+
+
 -- | Rotate vector by pi/2 clockwise.
 vNormal :: Point2 -> Point2
 {-# INLINE vNormal #-}