BUG: plot_surface ignores lightsource when cmap/facecolors are not specified · Issue #8877 · matplotlib/matplotlib · GitHub

Three different, undocumented, cases that I think should be the same:

plot_surface(..., shade=True, lightsource=..., cmap=..., facecolors="garbage") - uses LightSource.shade, which does some messy and unnecessary trig in LightSource.hillshade, using the orientation of the lightsource.
plot_surface(..., shade=True, lightsource=..., cmap=...) - uses _shade_colors, which does a more sensible vector-based approach, but hard-codes a [-1, -1, 0.5] normal vector, rather than respecting the lightsource direction.
plot_surface(..., shade=True, lightsource=..., facecolors="garbage") - as above

Regarding (2), I think that there is a typo in axes3d.py, and this change should be made:

         # Shade the data
-        if shade and cmap is not None and fcolors is not None:
+        if shade and cmap is not None and fcolors is None:
             fcolors = self._shade_colors_lightsource(Z, cmap, lightsource)

It seems dumb to only calculate face colors if the user already asked for different ones.

Regarding (3) - I think it would be useful to unify the shading into a normal-vector based approach, which I might try in a later patch

A demo:

import numpy as np
from matplotlib import pyplot as plt
from mpl_toolkits.mplot3d import Axes3D

x, y = np.mgrid[-2:2:5j,-2:2:5j]
z = x * y

Simple case, showing ignored argument:

fig, ax = plt.subplots(subplot_kw={"projection": "3d"})
ax.plot_surface(x, y, z, cmap='viridis', shade=True, lightsource='Literally anything')

Showing different shading passing in a unrelated argument. Also, cmap can't always be a string

fig, ax = plt.subplots(subplot_kw={"projection": "3d"})
ax.plot_surface(x, y, z, cmap='viridis', shade=True, facecolors="do it differently, ok?")
# TypeError: String object not callable
ax.plot_surface(x, y, z, cmap=plt.get_cmap('viridis'), shade=True,
    facecolors="do it differently, ok?")

Showing lightsource calculations being wrong - overhead light should result in symmetric shading:

from matplotlib.colors import LightSource
fig, ax = plt.subplots(subplot_kw={"projection": "3d"})
ax.plot_surface(x, y, z, cmap=plt.get_cmap('viridis'), shade=True,
   facecolors="do it differently, ok?", lightsource=LightSource(altdeg=90))

This should probably remain open until some image-comparison tests are added to confirm it is fixed. I suspect the last issue still persists

This issue has been marked "inactive" because it has been 365 days since the last comment. If this issue is still present in recent Matplotlib releases, or the feature request is still wanted, please leave a comment and this label will be removed. If there are no updates in another 30 days, this issue will be automatically closed, but you are free to re-open or create a new issue if needed. We value issue reports, and this procedure is meant to help us resurface and prioritize issues that have not been addressed yet, not make them disappear. Thanks for your help!

BUG: plot_surface ignores lightsource when cmap/facecolors are not specified · Issue #8877 · matplotlib/matplotlib · GitHub

Repository navigation

BUG: plot_surface ignores lightsource when cmap/facecolors are not specified #8877

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

BUG: plot_surface ignores lightsource when cmap/facecolors are not specified · Issue #8877 · matplotlib/matplotlib · GitHub

Repository navigation

BUG: plot_surface ignores lightsource when cmap/facecolors are not specified #8877

Description

Activity

eric-wieser commented on Jul 14, 2017

eric-wieser commented on Sep 16, 2018

github-actions commented on Apr 14, 2023

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions