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BUG: Fix non-square wireframe 3D plotting #31750

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Merged
tacaswell merged 1 commit into from
May 27, 2026
+20 −4
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BUG: Fix non-square wireframe 3D plotting #31750

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23 changes: 19 additions & 4 deletions lib/mpl_toolkits/mplot3d/art3d.py
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Original file line number Diff line number Diff line change
Expand Up @@ -497,15 +497,27 @@ def do_3d_projection(self):
"""
Project the points according to renderer matrix.
"""
segments = np.asanyarray(self._segments3d)
segments = self._segments3d

# Handle ragged inputs, but prefer a faster path for same-length segments
segment_lengths = [len(segment) for segment in segments]
ragged = len(set(segment_lengths)) > 1
if ragged:
# Branch masked / non-masked for speed

@QuLogic QuLogic May 26, 2026

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Did you benchmark this?

@scottshambaugh scottshambaugh May 26, 2026 •
edited
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Yeah, for large wireframes the overall function call is 20-30% faster when you skip creating a masked array (mostly due to split set_segments and min below, not in the concat here). The any check is cheap. Part of the reason I want to rip out masked arrays altogether, but that's for later #31008

@timhoffm timhoffm May 27, 2026

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If self._segments3d is already and array, you could skip the segment_length calculation.

@tacaswell tacaswell May 27, 2026

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I'm inclined to merge this as-is and optimize in follow on PRs to get 3.11 unblocked.

if any(np.ma.isMA(segment) for segment in segments):
segments = np.ma.concatenate(segments)
else:
segments = np.concatenate(segments)
else:
segments = np.asanyarray(segments)

# Handle empty segments
if segments.size == 0:
LineCollection.set_segments(self, [])
return np.nan

mask = False
if np.ma.isMA(segments):
if np.ma.isMA(segments) and segments.mask is not np.ma.nomask:
mask = segments.mask

if self._axlim_clip:
Expand All @@ -519,9 +531,12 @@ def do_3d_projection(self):
(*viewlim_mask.shape, 3))
mask = mask | viewlim_mask

xyzs = np.ma.array(
proj3d._scale_proj_transform_vectors(segments, self.axes), mask=mask)
xyzs = proj3d._scale_proj_transform_vectors(segments, self.axes)
if mask is not False:
xyzs = np.ma.array(xyzs, mask=mask)
segments_2d = xyzs[..., 0:2]
if ragged:
segments_2d = np.split(segments_2d, np.cumsum(segment_lengths[:-1]))
LineCollection.set_segments(self, segments_2d)

# FIXME
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Binary file modified ...pl_toolkits/mplot3d/tests/baseline_images/test_axes3d/wireframe3dasymmetric.png
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1 change: 1 addition & 0 deletions lib/mpl_toolkits/mplot3d/tests/test_axes3d.py
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Expand Up @@ -854,6 +854,7 @@ def test_wireframe3dasymmetric():
fig = plt.figure()
ax = fig.add_subplot(projection='3d')
X, Y, Z = axes3d.get_test_data(0.05)
X, Y, Z = X[:-1], Y[:-1], Z[:-1] # Drop a row so the grid is non-square
ax.plot_wireframe(X, Y, Z, rcount=3, ccount=13)


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