Merge pull request matplotlib#25272 from scottshambaugh/3d_exact_limits

Do not add padding to 3D axis limits when limits are manually set

Author: timhoffm

doc/api/toolkits/mplot3d/axes3d.rst

@@ -92,12 +92,18 @@ Axis limits and direction
 
    get_zaxis
    get_xlim
+   set_xlim
    get_ylim
+   set_ylim
    get_zlim
    set_zlim
    get_w_lims
    invert_zaxis
    zaxis_inverted
+   get_xbound
+   set_xbound
+   get_ybound
+   set_ybound
    get_zbound
    set_zbound
 

doc/users/next_whats_new/3d_axis_limits.rst

@@ -0,0 +1,18 @@
+Setting 3D axis limits now set the limits exactly
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Previously, setting the limits of a 3D axis would always add a small margin to
+the limits. Limits are now set exactly by default. The newly introduced rcparam
+``axes3d.automargin`` can be used to revert to the old behavior where margin is
+automatically added.
+
+.. plot::
+    :include-source: true
+    :alt: Example of the new behavior of 3D axis limits, and how setting the rcparam reverts to the old behavior.
+
+    import matplotlib.pyplot as plt
+    fig, axs = plt.subplots(1, 2, subplot_kw={'projection': '3d'})
+    plt.rcParams['axes3d.automargin'] = False  # the default in 3.9.0
+    axs[0].set(xlim=(0, 1), ylim=(0, 1), zlim=(0, 1), title='New Behavior')
+    plt.rcParams['axes3d.automargin'] = True
+    axs[1].set(xlim=(0, 1), ylim=(0, 1), zlim=(0, 1), title='Old Behavior')

lib/matplotlib/axis.py

@@ -840,13 +840,14 @@ def _get_autoscale_on(self):
     def _set_autoscale_on(self, b):
         """
         Set whether this Axis is autoscaled when drawing or by
-        `.Axes.autoscale_view`.
+        `.Axes.autoscale_view`. If b is None, then the value is not changed.
 
         Parameters
         ----------
         b : bool
         """
-        self._autoscale_on = b
+        if b is not None:
+            self._autoscale_on = b
 
     def get_children(self):
         return [self.label, self.offsetText,
@@ -1229,8 +1230,7 @@ def _set_lim(self, v0, v1, *, emit=True, auto):
         # Mark viewlims as no longer stale without triggering an autoscale.
         for ax in self._get_shared_axes():
             ax._stale_viewlims[name] = False
-        if auto is not None:
-            self._set_autoscale_on(bool(auto))
+        self._set_autoscale_on(auto)
 
         if emit:
             self.axes.callbacks.process(f"{name}lim_changed", self.axes)
@@ -1277,6 +1277,17 @@ def _update_ticks(self):
         if view_low > view_high:
             view_low, view_high = view_high, view_low
 
+        if (hasattr(self, "axes") and self.axes.name == '3d'
+                and mpl.rcParams['axes3d.automargin']):
+            # In mpl3.8, the margin was 1/48. Due to the change in automargin
+            # behavior in mpl3.9, we need to adjust this to compensate for a
+            # zoom factor of 2/48, giving us a 23/24 modifier. So the new
+            # margin is 0.019965277777777776 = 1/48*23/24.
+            margin = 0.019965277777777776
+            delta = view_high - view_low
+            view_high = view_high - delta * margin
+            view_low = view_low + delta * margin
+
         interval_t = self.get_transform().transform([view_low, view_high])
 
         ticks_to_draw = []

lib/matplotlib/mpl-data/matplotlibrc

@@ -425,8 +425,9 @@
 #axes.autolimit_mode: data  # If "data", use axes.xmargin and axes.ymargin as is.
                             # If "round_numbers", after application of margins, axis
                             # limits are further expanded to the nearest "round" number.
-#polaraxes.grid: True  # display grid on polar axes
-#axes3d.grid:    True  # display grid on 3D axes
+#polaraxes.grid:    True   # display grid on polar axes
+#axes3d.grid:       True   # display grid on 3D axes
+#axes3d.automargin: False  # automatically add margin when manually setting 3D axis limits
 
 #axes3d.xaxis.panecolor:    (0.95, 0.95, 0.95, 0.5)  # background pane on 3D axes
 #axes3d.yaxis.panecolor:    (0.90, 0.90, 0.90, 0.5)  # background pane on 3D axes

lib/matplotlib/mpl-data/stylelib/classic.mplstyle

@@ -223,7 +223,8 @@ axes.spines.left    : True
 axes.spines.right   : True
 axes.spines.top     : True
 polaraxes.grid      : True    # display grid on polar axes
-axes3d.grid         : True    # display grid on 3d axes
+axes3d.grid         : True    # display grid on 3D axes
+axes3d.automargin   : False   # automatically add margin when manually setting 3D axis limits
 
 date.autoformatter.year   : %Y
 date.autoformatter.month  : %b %Y

lib/matplotlib/rcsetup.py

@@ -1094,8 +1094,10 @@ def _convert_validator_spec(key, conv):
     "axes.ymargin": _validate_greaterthan_minushalf,  # margin added to yaxis
     "axes.zmargin": _validate_greaterthan_minushalf,  # margin added to zaxis
 
-    "polaraxes.grid": validate_bool,  # display polar grid or not
-    "axes3d.grid":    validate_bool,  # display 3d grid
+    "polaraxes.grid":    validate_bool,  # display polar grid or not
+    "axes3d.grid":       validate_bool,  # display 3d grid
+    "axes3d.automargin": validate_bool,  # automatically add margin when
+                                         # manually setting 3D axis limits
 
     "axes3d.xaxis.panecolor":    validate_color,  # 3d background pane
     "axes3d.yaxis.panecolor":    validate_color,  # 3d background pane

lib/matplotlib/tests/test_collections.py

@@ -401,6 +401,7 @@ def test_EllipseCollection():
 @image_comparison(['polycollection_close.png'], remove_text=True, style='mpl20')
 def test_polycollection_close():
     from mpl_toolkits.mplot3d import Axes3D  # type: ignore
+    plt.rcParams['axes3d.automargin'] = True
 
     vertsQuad = [
         [[0., 0.], [0., 1.], [1., 1.], [1., 0.]],

lib/matplotlib/ticker.py

@@ -2102,6 +2102,11 @@ def _raw_ticks(self, vmin, vmax):
             steps = steps[igood]
 
         raw_step = ((_vmax - _vmin) / nbins)
+        if hasattr(self.axis, "axes") and self.axis.axes.name == '3d':
+            # Due to the change in automargin behavior in mpl3.9, we need to
+            # adjust the raw step to match the mpl3.8 appearance. The zoom
+            # factor of 2/48, gives us the 23/24 modifier.
+            raw_step = raw_step * 23/24
         large_steps = steps >= raw_step
         if mpl.rcParams['axes.autolimit_mode'] == 'round_numbers':
             # Classic round_numbers mode may require a larger step.