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Ensure that Path.arc works for any full circle. #8994

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Merged
merged 4 commits into from
Aug 7, 2017
Merged

Ensure that Path.arc works for any full circle. #8994

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87c668a
Remove unnecessary math in Path.arc.
QuLogic Aug 6, 2017
5162f37
Ensure that Path.arc works for any full circle.
QuLogic Aug 6, 2017
c586b55
Update broken test images.
QuLogic Aug 6, 2017
e41d033
Document how Path.arc handles >360 degree arcs.
QuLogic Aug 7, 2017
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21 changes: 15 additions & 6 deletions lib/matplotlib/path.py
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Original file line number Diff line number Diff line change
Expand Up @@ -856,6 +856,10 @@ def arc(cls, theta1, theta2, n=None, is_wedge=False):
Return an arc on the unit circle from angle
*theta1* to angle *theta2* (in degrees).

*theta2* is unwrapped to produce the shortest arc within 360 degrees.
That is, if *theta2* > *theta1* + 360, the arc will be from *theta1* to
*theta2* - 360 and not a full circle plus some extra overlap.

If *n* is provided, it is the number of spline segments to make.
If *n* is not provided, the number of spline segments is
determined based on the delta between *theta1* and *theta2*.
Expand All @@ -864,14 +868,15 @@ def arc(cls, theta1, theta2, n=None, is_wedge=False):
polylines, quadratic or cubic Bezier curves
<http://www.spaceroots.org/documents/ellipse/index.html>`_.
"""
theta1, theta2 = np.deg2rad([theta1, theta2])

twopi = np.pi * 2.0
halfpi = np.pi * 0.5

eta1 = np.arctan2(np.sin(theta1), np.cos(theta1))
eta2 = np.arctan2(np.sin(theta2), np.cos(theta2))
eta2 -= twopi * np.floor((eta2 - eta1) / twopi)
eta1 = theta1
eta2 = theta2 - 360 * np.floor((theta2 - theta1) / 360)
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Why use floor instead of // ?

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There are a few edge cases where it's not the same, but I'm not sure if that's the reason. This is just a rearrangment of existing code changed from radians to degrees (because the trig is not necessary here.)

# Ensure 2pi range is not flattened to 0 due to floating-point errors,
# but don't try to expand existing 0 range.
if theta2 != theta1 and eta2 <= eta1:
eta2 += 360
eta1, eta2 = np.deg2rad([eta1, eta2])

# number of curve segments to make
if n is None:
Expand Down Expand Up @@ -930,6 +935,10 @@ def wedge(cls, theta1, theta2, n=None):
Return a wedge of the unit circle from angle
*theta1* to angle *theta2* (in degrees).

*theta2* is unwrapped to produce the shortest wedge within 360 degrees.
That is, if *theta2* > *theta1* + 360, the wedge will be from *theta1*
to *theta2* - 360 and not a full circle plus some extra overlap.

If *n* is provided, it is the number of spline segments to make.
If *n* is not provided, the number of spline segments is
determined based on the delta between *theta1* and *theta2*.
Expand Down
Binary file modified lib/matplotlib/tests/baseline_images/test_patches/wedge_range.pdf
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117 changes: 56 additions & 61 deletions lib/matplotlib/tests/baseline_images/test_patches/wedge_range.svg
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12 changes: 12 additions & 0 deletions lib/matplotlib/tests/test_path.py
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Expand Up @@ -205,3 +205,15 @@ def test_path_deepcopy():
path2 = Path(verts, codes)
copy.deepcopy(path1)
copy.deepcopy(path2)


@pytest.mark.parametrize('offset', range(-720, 361, 45))
def test_full_arc(offset):
low = offset
high = 360 + offset

path = Path.arc(low, high)
mins = np.min(path.vertices, axis=0)
maxs = np.max(path.vertices, axis=0)
np.testing.assert_allclose(mins, -1)
assert np.allclose(maxs, 1)