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[Bug]: Fix 3D surface corruption on non-linear scales by masking invalid values #31733

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[Bug]: Fix 3D surface corruption on non-linear scales by masking invalid values #31733

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cb8042d
Fix 3D surface corruption with non-linear scales by masking invalid v…
rahulrathnavel May 22, 2026
e175f8c
Fix TypeError by vectorizing val_in_range array checks
rahulrathnavel May 22, 2026
a4f7f33
Fix W293 trailing whitespace on blank line
rahulrathnavel May 22, 2026
6503bdc
Refactor scale masking into helper function and add tests
rahulrathnavel May 22, 2026
3aab848
Fix W293 trailing whitespace across refactored files
rahulrathnavel May 22, 2026
3cab332
Update 3D log scale test to assert dropped polygons
rahulrathnavel May 22, 2026
acc5892
Fix W293 trailing whitespace in 3D log scale test
rahulrathnavel May 22, 2026
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27 changes: 23 additions & 4 deletions lib/mpl_toolkits/mplot3d/axes3d.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2370,6 +2370,17 @@ def fill_between(self, x1, y1, z1, x2, y2, z2, *,
self.auto_scale_xyz([x1, x2], [y1, y2], [z1, z2], had_data)
return polyc

def _mask_invalid_scale_values(self, X, Y, Z):
"""Mask out values that are invalid for the current scale."""
val_in_range_X = np.vectorize(self.xaxis._scale.val_in_range, otypes=[bool])
val_in_range_Y = np.vectorize(self.yaxis._scale.val_in_range, otypes=[bool])
val_in_range_Z = np.vectorize(self.zaxis._scale.val_in_range, otypes=[bool])

X = np.where(val_in_range_X(X), X, np.nan)
Y = np.where(val_in_range_Y(Y), Y, np.nan)
Z = np.where(val_in_range_Z(Z), Z, np.nan)

@scottshambaugh scottshambaugh May 22, 2026

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This is fine for now since we're working a bug fix and want to limit changes. Being able to pass numpy arrays into val_in_range will be more efficient in the future.

return X, Y, Z

def plot_surface(self, X, Y, Z, *, norm=None, vmin=None,
vmax=None, lightsource=None, axlim_clip=False, **kwargs):
"""
Expand Down Expand Up @@ -2452,6 +2463,9 @@ def plot_surface(self, X, Y, Z, *, norm=None, vmin=None,

Z = cbook._to_unmasked_float_array(Z)
X, Y, Z = np.broadcast_arrays(X, Y, Z)

X, Y, Z = self._mask_invalid_scale_values(X, Y, Z)

rows, cols = Z.shape

has_stride = 'rstride' in kwargs or 'cstride' in kwargs
Expand Down Expand Up @@ -2618,6 +2632,9 @@ def plot_wireframe(self, X, Y, Z, *, axlim_clip=False, **kwargs):
raise ValueError("Argument Z must be 2-dimensional.")
# FIXME: Support masked arrays
X, Y, Z = np.broadcast_arrays(X, Y, Z)

X, Y, Z = self._mask_invalid_scale_values(X, Y, Z)

rows, cols = Z.shape

has_stride = 'rstride' in kwargs or 'cstride' in kwargs
Expand Down Expand Up @@ -2770,10 +2787,12 @@ def plot_trisurf(self, *args, color=None, norm=None, vmin=None, vmax=None,
z, *args = args
z = np.asarray(z)

tx, ty, tz = self._mask_invalid_scale_values(tri.x, tri.y, z)

triangles = tri.get_masked_triangles()
xt = tri.x[triangles]
yt = tri.y[triangles]
zt = z[triangles]
xt = tx[triangles]
yt = ty[triangles]
zt = tz[triangles]
verts = np.stack((xt, yt, zt), axis=-1)

if cmap:
Expand All @@ -2792,7 +2811,7 @@ def plot_trisurf(self, *args, color=None, norm=None, vmin=None, vmax=None,
facecolors=color, axlim_clip=axlim_clip, **kwargs)

self.add_collection(polyc, autolim="_datalim_only")
self.auto_scale_xyz(tri.x, tri.y, z, had_data)
self.auto_scale_xyz(tx, ty, tz, had_data)

return polyc

Expand Down
20 changes: 20 additions & 0 deletions lib/mpl_toolkits/mplot3d/tests/test_axes3d.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3189,3 +3189,23 @@ def test_scale3d_calc_coord():
# Pane coordinate should match axis limit (y-pane at max)
assert pane_idx == 1
assert point[pane_idx] == pytest.approx(ax.get_ylim()[1])


def test_3d_log_scale_negative_masking():
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')

# Set scales BEFORE plotting so the masking logic is triggered
ax.set_xscale('log')
ax.set_zscale('log')

# A 3x3 grid normally yields 4 polygons total
X, Y = np.meshgrid(np.linspace(-1, 1, 3), np.linspace(-1, 1, 3))
Z = X + Y

surf = ax.plot_surface(X, Y, Z)

# On main (broken), no values are masked, so all 4 polygons are generated.
# On our branch (fixed), the negative/zero values are masked to NaN,
# and plot_surface gracefully drops the invalid polygons.
assert len(surf.get_paths()) < 4
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