Fix marker overlap

xenoryt · jakeprojects · timhoffm · timhoffm · commit 4428da66f0db · 2020-05-10T19:38:04.000+02:00
Sort points by z coordinate values similar to Poly3DCollection

Co-authored-by: Jake Lee &lt;jake@sigmastatistics.co.uk&gt;
Co-authored-by: Tim Hoffmann &lt;2836374+timhoffm@users.noreply.github.com&gt;
diff --git a/lib/mpl_toolkits/mplot3d/art3d.py b/lib/mpl_toolkits/mplot3d/art3d.py
@@ -494,9 +494,27 @@ def do_3d_projection(self, renderer):
 
         ecs = (_zalpha(self._edgecolor3d, vzs) if self._depthshade else
                self._edgecolor3d)
+
+        # Sort the points based on z coordinates
+        # Performance optimization: Create a sorted index array and reorder
+        # points and point properties according to the index array
+        z_markers_idx = np.argsort(vzs)[::-1]
+
+        # Re-order items
+        vzs = vzs[z_markers_idx]
+        vxs = vxs[z_markers_idx]
+        vys = vys[z_markers_idx]
+        fcs = fcs[z_markers_idx]
+        ecs = ecs[z_markers_idx]
+        vps = np.column_stack((vxs, vys))
+
+        fcs = mcolors.to_rgba_array(fcs, self._alpha)
         ecs = mcolors.to_rgba_array(ecs, self._alpha)
+
         self.set_edgecolors(ecs)
-        PathCollection.set_offsets(self, np.column_stack([vxs, vys]))
+        self.set_facecolors(fcs)
+
+        PathCollection.set_offsets(self, vps)
 
         return np.min(vzs) if vzs.size else np.nan
 
@@ -663,17 +681,16 @@ def do_3d_projection(self, renderer):
              in enumerate(zip(xyzlist, cface, cedge))),
             key=lambda x: x[0], reverse=True)
 
-        segments_2d = [s for z, s, fc, ec, idx in z_segments_2d]
+        zzs, segments_2d, self._facecolors2d, self._edgecolors2d, idxs = \
+            zip(*z_segments_2d)
+
         if self._codes3d is not None:
-            codes = [self._codes3d[idx] for z, s, fc, ec, idx in z_segments_2d]
+            codes = [self._codes3d[idx] for idx in idxs]
             PolyCollection.set_verts_and_codes(self, segments_2d, codes)
         else:
             PolyCollection.set_verts(self, segments_2d, self._closed)
 
-        self._facecolors2d = [fc for z, s, fc, ec, idx in z_segments_2d]
-        if len(self._edgecolors3d) == len(cface):
-            self._edgecolors2d = [ec for z, s, fc, ec, idx in z_segments_2d]
-        else:
+        if len(self._edgecolors3d) != len(cface):
             self._edgecolors2d = self._edgecolors3d
 
         # Return zorder value
diff --git a/lib/mpl_toolkits/tests/test_mplot3d.py b/lib/mpl_toolkits/tests/test_mplot3d.py
@@ -230,6 +230,51 @@ def test_scatter3d_color():
                color='b', marker='s')
 
 
+@pytest.mark.parametrize('azim', [-50, 130])  # yellow first, blue first
+@check_figures_equal(extensions=['png'])
+def test_marker_draw_order_data_reversed(fig_test, fig_ref, azim):
+    """
+    Test that the draw order does not depend on the data point order.
+
+    For the given viewing angle at azim=-50, the yellow marker should be in
+    front. For azim=130, the blue marker should be in front.
+    """
+    x = [-1, 1]
+    y = [1, -1]
+    z = [0, 0]
+    color = ['b', 'y']
+    ax = fig_test.add_subplot(projection='3d')
+    ax.scatter(x, y, z, s=3500, c=color)
+    ax.view_init(elev=0, azim=azim)
+    ax = fig_ref.add_subplot(projection='3d')
+    ax.scatter(x[::-1], y[::-1], z[::-1], s=3500, c=color[::-1])
+    ax.view_init(elev=0, azim=azim)
+
+
+@check_figures_equal(extensions=['png'])
+def test_marker_draw_order_view_rotated(fig_test, fig_ref):
+    """
+    Test that the draw order changes with the direction.
+
+    If we rotate *azim* by 180 degrees and exchange the colors, the plot
+    plot should look the same again.
+    """
+    azim = 130
+    x = [-1, 1]
+    y = [1, -1]
+    z = [0, 0]
+    color = ['b', 'y']
+    ax = fig_test.add_subplot(projection='3d')
+    # axis are not exactly invariant under 180 degree rotation -> deactivate
+    ax.set_axis_off()
+    ax.scatter(x, y, z, s=3500, c=color)
+    ax.view_init(elev=0, azim=azim)
+    ax = fig_ref.add_subplot(projection='3d')
+    ax.set_axis_off()
+    ax.scatter(x, y, z, s=3500, c=color[::-1])  # color reversed
+    ax.view_init(elev=0, azim=azim - 180)  # view rotated by 180 degrees
+
+
 @mpl3d_image_comparison(['plot_3d_from_2d.png'], tol=0.01)
 def test_plot_3d_from_2d():
     fig = plt.figure()
