matplotlib · patquem · Mar 25, 2022
diff --git a/lib/mpl_toolkits/mplot3d/axes3d.py b/lib/mpl_toolkits/mplot3d/axes3d.py
@@ -273,22 +273,16 @@ def set_aspect(self, aspect, adjustable=None, anchor=None, share=False):
        """
        Set the aspect ratios.

-        Axes 3D does not current support any aspect but 'auto' which fills
-        the Axes with the data limits.
-
-        To simulate having equal aspect in data space, set the ratio
-        of your data limits to match the value of `.get_box_aspect`.
-        To control box aspect ratios use `~.Axes3D.set_box_aspect`.
-
        Parameters
        ----------
-        aspect : {'auto'}
+        aspect : {'auto', 'equal'}
            Possible values:

            =========   ==================================================
            value       description
            =========   ==================================================
            'auto'      automatic; fill the position rectangle with data.
+            'equal'     automatic; adapt the axes to have equal aspect
            =========   ==================================================

        adjustable : None
@@ -322,14 +316,27 @@ def set_aspect(self, aspect, adjustable=None, anchor=None, share=False):
        --------
        mpl_toolkits.mplot3d.axes3d.Axes3D.set_box_aspect
        """
-        if aspect != 'auto':
+        if aspect not in ['auto', 'equal']:
            raise NotImplementedError(
                "Axes3D currently only supports the aspect argument "
-                f"'auto'. You passed in {aspect!r}."
+                f"'auto' or 'equal'. You passed in {aspect!r}."
            )
        super().set_aspect(
            aspect, adjustable=adjustable, anchor=anchor, share=share)

+        if aspect == 'equal':
+            self.set_box_aspect((1., 1., 1.))
+            v_intervals = np.vstack((self.xaxis.get_view_interval(),
+                                     self.yaxis.get_view_interval(),
+                                     self.zaxis.get_view_interval())).T
+            mean = np.mean(v_intervals, axis=0)
+            delta = np.max(np.max(v_intervals, axis=0) -
+                           np.min(v_intervals, axis=0))
+
+            self.set_xlim3d(mean[0] - delta / 2., mean[0] + delta / 2.)
+            self.set_ylim3d(mean[1] - delta / 2., mean[1] + delta / 2.)
+            self.set_zlim3d(mean[2] - delta / 2., mean[2] + delta / 2.)
+
    def set_box_aspect(self, aspect, *, zoom=1):
        """
        Set the Axes box aspect.

diff --git a/lib/mpl_toolkits/tests/baseline_images/test_mplot3d/aspect_equal.png b/lib/mpl_toolkits/tests/baseline_images/test_mplot3d/aspect_equal.png
diff --git a/lib/mpl_toolkits/tests/test_mplot3d.py b/lib/mpl_toolkits/tests/test_mplot3d.py
@@ -21,11 +21,27 @@
    image_comparison, remove_text=True, style='default')


-def test_aspect_equal_error():
+@mpl3d_image_comparison(['aspect_equal.png'], remove_text=False)
+def test_aspect_equal():
    fig = plt.figure()
    ax = fig.add_subplot(projection='3d')
-    with pytest.raises(NotImplementedError):
-        ax.set_aspect('equal')
+
+    points = np.array([[0, 0, 0], [1, 0, 0], [0, 1, 0], [1, 1, 0],
+                       [0, 0, 3], [1, 0, 3], [0, 1, 3], [1, 1, 3]])
+
+    x = np.asarray([coord[0] for coord in points])
+    y = np.asarray([coord[1] for coord in points])
+    z = np.asarray([coord[2] for coord in points])
+
+    def plot_edge(i, j):
+        ax.plot([x[i], x[j]], [y[i], y[j]], [z[i], z[j]], c='r')
+
+    # hexaedron creation
+    plot_edge(0, 1), plot_edge(1, 3), plot_edge(3, 2), plot_edge(2, 0)
+    plot_edge(4, 5), plot_edge(5, 7), plot_edge(7, 6), plot_edge(6, 4)
+    plot_edge(0, 4), plot_edge(1, 5), plot_edge(3, 7), plot_edge(2, 6)
+
+    ax.set_aspect('equal')


 @mpl3d_image_comparison(['bar3d.png'])