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feat(3d): improve plot_surface shading logic #30424

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feat(3d): improve plot_surface shading logic #30424

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d38efb3
feat(3d): improve plot_surface shading logic
MengAiDev Aug 14, 2025
f360b4f
fix
MengAiDev Aug 14, 2025
3e7a740
lint fix
MengAiDev Aug 14, 2025
bc0bb49
Update lib/mpl_toolkits/mplot3d/axes3d.py
MengAiDev Aug 30, 2025
e3f00de
solve conversation
MengAiDev Aug 31, 2025
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21 changes: 15 additions & 6 deletions lib/mpl_toolkits/mplot3d/axes3d.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2198,9 +2198,12 @@ def plot_surface(self, X, Y, Z, *, norm=None, vmin=None,
vmin, vmax : float, optional
Bounds for the normalization.

shade : bool, default: True
Whether to shade the facecolors. Shading is always disabled when
*cmap* is specified.
shade : bool or "auto", default: "auto"
Whether to shade the facecolors. "auto" will shade only if the facecolor
is uniform, i.e. neither *cmap* nor *facecolors* is given.

Furthermore, shading is generally not compatible with colormapping
and ``shade=True, cmap=...`` will raise an error.

lightsource : `~matplotlib.colors.LightSource`, optional
The lightsource to use when *shade* is True.
Expand Down Expand Up @@ -2251,9 +2254,15 @@ def plot_surface(self, X, Y, Z, *, norm=None, vmin=None,
fcolors = kwargs.pop('facecolors', None)

cmap = kwargs.get('cmap', None)
shade = kwargs.pop('shade', cmap is None)
if shade is None:
raise ValueError("shade cannot be None.")
shade = kwargs.pop('shade', 'auto')
if shade == "auto":
shade = cmap is None and fcolors is None
# Remove the None check as it doesn't seem to be needed

# Raise error if shade=True and cmap is provided as documented
Comment on lines +2260 to +2262
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Suggested change
# Remove the None check as it doesn't seem to be needed
# Raise error if shade=True and cmap is provided as documented

These comments do note make sense. AFAICS the first is a relic, the second only restates what the code does

if shade is True and cmap is not None:
raise ValueError("Shading is not compatible with colormapping. "
"Set shade=False or do not provide a cmap.")

colset = [] # the sampled facecolor
if (rows - 1) % rstride == 0 and \
Expand Down
86 changes: 85 additions & 1 deletion lib/mpl_toolkits/mplot3d/tests/test_axes3d.py
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Expand Up @@ -703,7 +703,7 @@ def test_surface3d_masked():
z = np.ma.masked_less(matrix, 0)
norm = mcolors.Normalize(vmax=z.max(), vmin=z.min())
colors = mpl.colormaps["plasma"](norm(z))
ax.plot_surface(x, y, z, facecolors=colors)
ax.plot_surface(x, y, z, facecolors=colors, shade=True)
ax.view_init(30, -80, 0)


Expand Down Expand Up @@ -2689,3 +2689,87 @@ def test_ndarray_color_kwargs_value_error():
ax = fig.add_subplot(111, projection='3d')
ax.scatter(1, 0, 0, color=np.array([0, 0, 0, 1]))
fig.canvas.draw()


@check_figures_equal()
def test_plot_surface_shade_auto_with_facecolors(fig_test, fig_ref):
"""Test that plot_surface with facecolors uses shade=False by default."""
X = np.linspace(0, 1, 5)
Y = np.linspace(0, 1, 5)
X_mesh, Y_mesh = np.meshgrid(X, Y)
Z = X_mesh + Y_mesh
colors = cm.viridis(X_mesh)

# Test with facecolors (should have shade=False by default)
ax_test = fig_test.add_subplot(projection='3d')
ax_test.plot_surface(X_mesh, Y_mesh, Z, facecolors=colors)

# Reference with explicit shade=False
ax_ref = fig_ref.add_subplot(projection='3d')
ax_ref.plot_surface(X_mesh, Y_mesh, Z, facecolors=colors, shade=False)


@check_figures_equal()
def test_plot_surface_shade_auto_without_facecolors(fig_test, fig_ref):
"""Test that plot_surface without facecolors uses shade=True by default."""
X = np.linspace(0, 1, 5)
Y = np.linspace(0, 1, 5)
X_mesh, Y_mesh = np.meshgrid(X, Y)
Z = X_mesh + Y_mesh

# Test without facecolors (should have shade=True by default)
ax_test = fig_test.add_subplot(projection='3d')
ax_test.plot_surface(X_mesh, Y_mesh, Z)

# Reference with explicit shade=True
ax_ref = fig_ref.add_subplot(projection='3d')
ax_ref.plot_surface(X_mesh, Y_mesh, Z, shade=True)


@check_figures_equal()
def test_plot_surface_shade_auto_with_cmap(fig_test, fig_ref):
"""Test that plot_surface with cmap uses shade=False by default."""
X = np.linspace(0, 1, 5)
Y = np.linspace(0, 1, 5)
X_mesh, Y_mesh = np.meshgrid(X, Y)
Z = X_mesh + Y_mesh

# Test with cmap (should have shade=False by default)
ax_test = fig_test.add_subplot(projection='3d')
ax_test.plot_surface(X_mesh, Y_mesh, Z, cmap=cm.viridis)

# Reference with explicit shade=False
ax_ref = fig_ref.add_subplot(projection='3d')
ax_ref.plot_surface(X_mesh, Y_mesh, Z, cmap=cm.viridis, shade=False)


@check_figures_equal()
def test_plot_surface_shade_override_with_facecolors(fig_test, fig_ref):
"""Test that explicit shade parameter overrides auto behavior with facecolors."""
X = np.linspace(0, 1, 5)
Y = np.linspace(0, 1, 5)
X_mesh, Y_mesh = np.meshgrid(X, Y)
Z = X_mesh + Y_mesh
colors = cm.viridis(X_mesh)

# Test with explicit shade=True (overrides auto behavior)
ax_test = fig_test.add_subplot(projection='3d')
ax_test.plot_surface(X_mesh, Y_mesh, Z, facecolors=colors, shade=True)

# Reference with explicit shade=True
ax_ref = fig_ref.add_subplot(projection='3d')
ax_ref.plot_surface(X_mesh, Y_mesh, Z, facecolors=colors, shade=True)


def test_plot_surface_shade_with_cmap_raises():
"""Test that shade=True with cmap raises an error."""
X = np.linspace(0, 1, 5)
Y = np.linspace(0, 1, 5)
X_mesh, Y_mesh = np.meshgrid(X, Y)
Z = X_mesh + Y_mesh

fig = plt.figure()
ax = fig.add_subplot(projection='3d')

with pytest.raises(ValueError, match="Shading is not compatible with colormapping"):
ax.plot_surface(X_mesh, Y_mesh, Z, cmap=cm.viridis, shade=True)
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