Backport PR #18505: Fix depth shading when edge/facecolor is none.

jklymak · meeseeksmachine · commit a7ea0440c2bd · 2020-09-17T16:14:23.000Z
diff --git a/lib/mpl_toolkits/mplot3d/art3d.py b/lib/mpl_toolkits/mplot3d/art3d.py
@@ -803,7 +803,7 @@ def _zalpha(colors, zs):
     #        in all three dimensions. Otherwise, at certain orientations,
     #        the min and max zs are very close together.
     #        Should really normalize against the viewing depth.
-    if len(zs) == 0:
+    if len(colors) == 0 or len(zs) == 0:
         return np.zeros((0, 4))
     norm = Normalize(min(zs), max(zs))
     sats = 1 - norm(zs) * 0.7
diff --git a/lib/mpl_toolkits/tests/test_mplot3d.py b/lib/mpl_toolkits/tests/test_mplot3d.py
@@ -237,8 +237,14 @@ def test_scatter3d():
 def test_scatter3d_color():
     fig = plt.figure()
     ax = fig.add_subplot(111, projection='3d')
+
+    # Check that 'none' color works; these two should overlay to produce the
+    # same as setting just `color`.
+    ax.scatter(np.arange(10), np.arange(10), np.arange(10),
+               facecolor='r', edgecolor='none', marker='o')
     ax.scatter(np.arange(10), np.arange(10), np.arange(10),
-               color='r', marker='o')
+               facecolor='none', edgecolor='r', marker='o')
+
     ax.scatter(np.arange(10, 20), np.arange(10, 20), np.arange(10, 20),
                color='b', marker='s')
 
