Merge pull request matplotlib#20416 from slavoutich/fix/patch3dcollection_z_marker_idx_missing

Fix missing Patch3DCollection._z_markers_idx

Author: jklymak

lib/mpl_toolkits/mplot3d/art3d.py

@@ -462,6 +462,7 @@ def set_3d_properties(self, zs, zdir):
             xs = []
             ys = []
         self._offsets3d = juggle_axes(xs, ys, np.atleast_1d(zs), zdir)
+        self._z_markers_idx = slice(-1)
         self._vzs = None
         self.stale = True
 

lib/mpl_toolkits/tests/test_mplot3d.py

@@ -601,22 +601,26 @@ def test_patch_modification():
 @check_figures_equal(extensions=['png'])
 def test_patch_collection_modification(fig_test, fig_ref):
     # Test that modifying Patch3DCollection properties after creation works.
-    patch = Circle((0, 0), 0.05)
-    c = art3d.Patch3DCollection([patch], linewidths=3)
+    patch1 = Circle((0, 0), 0.05)
+    patch2 = Circle((0.1, 0.1), 0.03)
+    facecolors = np.array([[0., 0.5, 0., 1.], [0.5, 0., 0., 0.5]])
+    c = art3d.Patch3DCollection([patch1, patch2], linewidths=3)
 
     ax_test = fig_test.add_subplot(projection='3d')
     ax_test.add_collection3d(c)
     c.set_edgecolor('C2')
-    c.set_facecolor('C3')
+    c.set_facecolor(facecolors)
     c.set_alpha(0.7)
     assert c.get_depthshade()
     c.set_depthshade(False)
     assert not c.get_depthshade()
 
-    patch = Circle((0, 0), 0.05)
-    c = art3d.Patch3DCollection([patch], linewidths=3,
-                                edgecolor='C2', facecolor='C3', alpha=0.7,
-                                depthshade=False)
+    patch1 = Circle((0, 0), 0.05)
+    patch2 = Circle((0.1, 0.1), 0.03)
+    facecolors = np.array([[0., 0.5, 0., 1.], [0.5, 0., 0., 0.5]])
+    c = art3d.Patch3DCollection([patch1, patch2], linewidths=3,
+                                edgecolor='C2', facecolor=facecolors,
+                                alpha=0.7, depthshade=False)
 
     ax_ref = fig_ref.add_subplot(projection='3d')
     ax_ref.add_collection3d(c)