BUG: Fix the aspect ratio of 3d plots

eric-wieser · eric-wieser · commit 4479a0ffe1b8 · 2020-02-11T16:17:23.000Z
Fixes gh-8894, by always using a "position" that maintains a uniform coordinate system. Test added - when viewed from above, the plot should be square not rhombic.
diff --git a/doc/users/next_whats_new/2019-03-25-mplot3d-projection.rst b/doc/users/next_whats_new/2019-03-25-mplot3d-projection.rst
@@ -0,0 +1,9 @@
+``Axes3D`` no longer distorts the 3d plot to match the 2d aspect ratio
+----------------------------------------------------------------------
+
+Plots made with :class:`~mpl_toolkits.mplot3d.axes3d.Axes3D` were previously
+stretched to fit a square bounding box. As this stretching was done after
+the projection from 3D to 2D, it resulted in distorted images if non-square
+bounding boxes were used.
+
+As of this release, this no longer occurs.
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -1499,9 +1499,9 @@ def apply_aspect(self, position=None):
         """
         Adjust the Axes for a specified data aspect ratio.
 
-        Depending on `.get_adjustable` this will modify either the Axes box
-        (position) or the view limits. In the former case, `.get_anchor`
-        will affect the position.
+        Depending on `.get_adjustable` this will modify either the
+        Axes box (position) or the view limits. In the former case,
+        `~matplotlib.axes.Axes.get_anchor` will affect the position.
 
         Notes
         -----
diff --git a/lib/mpl_toolkits/mplot3d/axes3d.py b/lib/mpl_toolkits/mplot3d/axes3d.py
@@ -255,6 +255,20 @@ def tunit_edges(self, vals=None, M=None):
                  (tc[7], tc[4])]
         return edges
 
+    def apply_aspect(self, position=None):
+        if position is None:
+            position = self.get_position(original=True)
+
+        # in the superclass, we would go through and actually deal with axis
+        # scales and box/datalim. Those are all irrelevant - all we need to do
+        # is make sure our coordinate system is square.
+        figW, figH = self.get_figure().get_size_inches()
+        fig_aspect = figH / figW
+        box_aspect = 1
+        pb = position.frozen()
+        pb1 = pb.shrunk_to_aspect(box_aspect, pb, fig_aspect)
+        self.set_position(pb1.anchored(self.get_anchor(), pb), 'active')
+
     @artist.allow_rasterization
     def draw(self, renderer):
         # draw the background patch
diff --git a/lib/mpl_toolkits/tests/test_mplot3d.py b/lib/mpl_toolkits/tests/test_mplot3d.py
@@ -511,6 +511,13 @@ def test_axes3d_cla():
     ax.cla()  # make sure the axis displayed is 3D (not 2D)
 
 
+@image_comparison(['axes3d_rotated.png'])
+def test_axes3d_rotated():
+    fig = plt.figure()
+    ax = fig.add_subplot(1, 1, 1, projection='3d')
+    ax.view_init(90, 45)  # look down, rotated. Should be square
+
+
 def test_plotsurface_1d_raises():
     x = np.linspace(0.5, 10, num=100)
     y = np.linspace(0.5, 10, num=100)
