Additional code review changes

Author: scottshambaugh

doc/users/next_whats_new/3d_plot_focal_length.rst

@@ -2,24 +2,25 @@ Give the 3D camera a custom focal length
 ----------------------------------------
 
 Users can now better mimic real-world cameras by specifying the focal length of
-the virtual camera in 3D plots. An increasing focal length between 1 and
-infinity "flattens" the image, while a decreasing focal length between 1 and 0
-exaggerates the perspective and gives the image more apparent depth. The
-default focal length of 1 corresponds to a Field of View (FOV) of 90 deg, and
-is backwards-compatible with existing 3D plots.
+the virtual camera in 3D plots. The default focal length of 1 corresponds to a
+Field of View (FOV) of 90 deg, and is backwards-compatible with existing 3D
+plots. An increased focal length between 1 and infinity "flattens" the image,
+while a decreased focal length between 1 and 0 exaggerates the perspective and
+gives the image more apparent depth.
 
 The focal length can be calculated from a desired FOV via the equation:
 
 .. mathmpl::
 
-    focal\_length = 1/tan(FOV/2)
+    focal\_length = 1/\tan(FOV/2)
 
 .. plot::
     :include-source: true
 
     from mpl_toolkits.mplot3d import axes3d
     import matplotlib.pyplot as plt
-    fig, axs = plt.subplots(1, 3, subplot_kw={'projection': '3d'})
+    fig, axs = plt.subplots(1, 3, subplot_kw={'projection': '3d'},
+                            constrained_layout=True)
     X, Y, Z = axes3d.get_test_data(0.05)
     focal_lengths = [0.25, 1, 4]
     for ax, fl in zip(axs, focal_lengths):

examples/mplot3d/projections.py

@@ -4,13 +4,13 @@
 ========================
 
 Demonstrates the different camera projections for 3D plots, and the effects of
-changing the focal length for a perspective projection. Note that matplotlib
+changing the focal length for a perspective projection. Note that Matplotlib
 corrects for the 'zoom' effect of changing the focal length.
 
-An increasing focal length between 1 and infinity "flattens" the image, while
-a decreasing focal length between 1 and 0 exaggerates the perspective and gives
-the image more apparent depth. The default focal length of 1 corresponds to a
-Field of View (FOV) of 90 deg. In the limiting case, a focal length of
+The default focal length of 1 corresponds to a Field of View (FOV) of 90 deg.
+An increased focal length between 1 and infinity "flattens" the image, while a
+decreased focal length between 1 and 0 exaggerates the perspective and gives
+the image more apparent depth. In the limiting case, a focal length of
 infinity corresponds to an orthographic projection after correction of the
 zoom effect.
 

lib/mpl_toolkits/mplot3d/axes3d.py

@@ -1013,12 +1013,11 @@ def set_proj_type(self, proj_type, focal_length=None):
         _api.check_in_list(['persp', 'ortho'], proj_type=proj_type)
         if proj_type == 'persp':
             if focal_length is None:
-                self._focal_length = 1
-            else:
-                if focal_length <= 0:
-                    raise ValueError(f"focal_length = {focal_length} must be"
-                                     " greater than 0")
-                self._focal_length = focal_length
+                focal_length = 1
+            elif focal_length <= 0:
+                raise ValueError(f"focal_length = {focal_length} must be "
+                                 "greater than 0")
+            self._focal_length = focal_length
         elif proj_type == 'ortho':
             if focal_length not in (None, np.inf):
                 raise ValueError(f"focal_length = {focal_length} must be "