Replace Holroyd by Bell

Gavin Bell appears to be the accurate reference/attribution, not Holroyd, replace it.
scottshambaugh · Oct 15, 2024 · Jul 10, 2024 · Sep 27, 2024 · Oct 1, 2024 · Oct 1, 2024
commit a293e31bea61607be481d8889ad84db2a88ca113
diff --git a/doc/api/toolkits/mplot3d/view_angles.rst b/doc/api/toolkits/mplot3d/view_angles.rst
@@ -83,8 +83,9 @@ mouse movement (it is quite noticeable, especially when adjusting roll),
 and it lacks an obvious mechanical equivalent; arguably, the path-independent rotation is unnatural.
 So it is a trade-off.
 
-Shoemake's arcball has an abrupt edge; this is remedied in Holroyd's arcball
-(``mouserotationstyle: Holroyd``).
+Shoemake's arcball has an abrupt edge; this is remedied in Gavin Bell's arcball
+(``mouserotationstyle: Bell``), originally written for OpenGL [Bell1988]_. It is used
+in Blender and Meshlab.
 
 Henriksen et al. [Henriksen2002]_ provide an overview. In summary:
 
@@ -122,7 +123,7 @@ Henriksen et al. [Henriksen2002]_ provide an overview. In summary:
      - ✔️
      - ✔️
      - ❌
-   * - Holroyd
+   * - Bell
      - ❌
      - ✔️
      - ✔️
@@ -142,7 +143,7 @@ You can try out one of the various mouse rotation styles using::
 .. code::
 
     import matplotlib as mpl
-    mpl.rcParams['axes3d.mouserotationstyle'] = 'trackball'  # 'azel', 'trackball', 'arcball', 'Shoemake', or 'Holroyd'
+    mpl.rcParams['axes3d.mouserotationstyle'] = 'trackball'  # 'azel', 'trackball', 'arcball', 'Shoemake', or 'Bell'
 
     import numpy as np
     import matplotlib.pyplot as plt
@@ -183,11 +184,14 @@ A size of about 2/3 appears to work reasonably well; this is the default.
   three-dimensional rotation using a mouse", in Proceedings of Graphics
   Interface '92, 1992, pp. 151-156, https://doi.org/10.20380/GI1992.18
 
+
+.. [Bell1988] Gavin Bell, in the examples included with the GLUT (OpenGL
+  Utility Toolkit) library,
+  https://github.com/markkilgard/glut/blob/master/progs/examples/trackball.h
+
 .. [Henriksen2002] Knud Henriksen, Jon Sporring, Kasper Hornbæk,
-  "Virtual Trackballs Revisited", in Proceedings of DSAGM'2002
-  `[pdf]`__;
-  and in IEEE Transactions on Visualization and Computer Graphics,
-  Volume 10, Issue 2, March-April 2004, pp. 206-216,
-  https://doi.org/10.1109/TVCG.2004.1260772
+  "Virtual Trackballs Revisited", in IEEE Transactions on Visualization
+  and Computer Graphics, Volume 10, Issue 2, March-April 2004, pp. 206-216,
+  https://doi.org/10.1109/TVCG.2004.1260772 `[full-text]`__;
 
-__ https://web.archive.org/web/20240607102518/http://hjemmesider.diku.dk/~kash/papers/DSAGM2002_henriksen.pdf
+__ https://www.researchgate.net/publication/8329656_Virtual_Trackballs_Revisited#fullTextFileContent
diff --git a/doc/users/next_whats_new/mouse_rotation.rst b/doc/users/next_whats_new/mouse_rotation.rst
@@ -20,7 +20,7 @@ To try out one of the various mouse rotation styles:
 .. code::
 
     import matplotlib as mpl
-    mpl.rcParams['axes3d.mouserotationstyle'] = 'trackball'  # 'azel', 'trackball', 'arcball', 'Shoemake', or 'Holroyd'
+    mpl.rcParams['axes3d.mouserotationstyle'] = 'trackball'  # 'azel', 'trackball', 'arcball', 'Shoemake', or 'Bell'
 
     import numpy as np
     import matplotlib.pyplot as plt

diff --git a/lib/matplotlib/mpl-data/matplotlibrc b/lib/matplotlib/mpl-data/matplotlibrc
@@ -433,7 +433,7 @@
 #axes3d.yaxis.panecolor:    (0.90, 0.90, 0.90, 0.5)  # background pane on 3D axes
 #axes3d.zaxis.panecolor:    (0.925, 0.925, 0.925, 0.5)  # background pane on 3D axes
 
-#axes3d.mouserotationstyle: arcball  # {azel, trackball, arcball, Shoemake, Holroyd}
+#axes3d.mouserotationstyle: arcball  # {azel, trackball, arcball, Shoemake, Bell}
                             # See also https://matplotlib.org/stable/api/toolkits/mplot3d/view_angles.html#rotation-with-mouse
 #axes3d.trackballsize: 0.667  # trackball diameter, in units of the Axes bbox
 

diff --git a/lib/matplotlib/rcsetup.py b/lib/matplotlib/rcsetup.py
@@ -1133,7 +1133,7 @@ def _convert_validator_spec(key, conv):
     "axes3d.zaxis.panecolor":    validate_color,  # 3d background pane
 
     "axes3d.mouserotationstyle": ["azel", "trackball", "arcball",
-                                  "Shoemake", "Holroyd"],
+                                  "Shoemake", "Bell"],
     "axes3d.trackballsize": validate_float,
 
     # scatter props

diff --git a/lib/mpl_toolkits/mplot3d/axes3d.py b/lib/mpl_toolkits/mplot3d/axes3d.py
@@ -1513,7 +1513,7 @@ def _arcball(self, x: float, y: float, style: str) -> np.ndarray:
         Convert a point (x, y) to a point on a virtual trackball.
 
         This is either Ken Shoemake's arcball (a sphere) or
-        Tom Holroyd's (a sphere combined with a hyperbola).
+        Gavin Bell's (a sphere combined with a hyperbola).
         See: Ken Shoemake, "ARCBALL: A user interface for specifying
         three-dimensional rotation using a mouse." in
         Proceedings of Graphics Interface '92, 1992, pp. 151-156,
@@ -1523,7 +1523,7 @@ def _arcball(self, x: float, y: float, style: str) -> np.ndarray:
         x /= s
         y /= s
         r2 = x*x + y*y
-        if style == 'Holroyd':
+        if style == 'Bell':
             if r2 > 0.5:
                 p = np.array([1/(2*math.sqrt(r2)), x, y])/math.sqrt(1/(4*r2)+r2)
             else:
@@ -1587,12 +1587,12 @@ def _on_move(self, event):
                     nk = np.linalg.norm(k)
                     th = nk / mpl.rcParams['axes3d.trackballsize']
                     dq = _Quaternion(np.cos(th), k*np.sin(th)/nk)
-                else:  # 'arcball', 'Shoemake', 'Holroyd'
+                else:  # 'arcball', 'Shoemake', 'Bell'
                     current_vec = self._arcball(self._sx/w, self._sy/h, style)
                     new_vec = self._arcball(x/w, y/h, style)
                     if style == 'arcball':
                         dq = _Quaternion.rotate_from_to(current_vec, new_vec)
-                    else:  # 'Shoemake', 'Holroyd'
+                    else:  # 'Shoemake', 'Bell'
                         dq = _Quaternion(0, new_vec) * _Quaternion(0, -current_vec)
 
                 q = dq * q

diff --git a/lib/mpl_toolkits/mplot3d/tests/test_axes3d.py b/lib/mpl_toolkits/mplot3d/tests/test_axes3d.py
@@ -1944,7 +1944,7 @@ def test_quaternion():
 
 
 @pytest.mark.parametrize('style',
-                         ('azel', 'trackball', 'arcball', 'Shoemake', 'Holroyd'))
+                         ('azel', 'trackball', 'arcball', 'Shoemake', 'Bell'))
 def test_rotate(style):
     """Test rotating using the left mouse button."""
     if style == 'azel':
@@ -2008,13 +2008,13 @@ def test_rotate(style):
                 ('Shoemake', 30, 0, 1): (-48.590378, -40.893395, 49.106605),
                 ('Shoemake', 30, 0.5, c): (-25.658906, -56.309932, 43.897886),
 
-                ('Holroyd', 0, 1, 0): (0, -60, 0),
-                ('Holroyd', 0, 0, 1): (-60, 0, 0),
-                ('Holroyd', 0, 0.5, c): (-48.590378, -40.893395, 19.106605),
-                ('Holroyd', 0, 2, 0): (0, -126.869898, 0),
-                ('Holroyd', 30, 1, 0):  (25.658906, -56.309932, 16.102114),
-                ('Holroyd', 30, 0, 1): (-48.590378, -40.893395, 49.106605),
-                ('Holroyd', 30, 0.5, c): (-25.658906, -56.309932, 43.897886)}
+                ('Bell', 0, 1, 0): (0, -60, 0),
+                ('Bell', 0, 0, 1): (-60, 0, 0),
+                ('Bell', 0, 0.5, c): (-48.590378, -40.893395, 19.106605),
+                ('Bell', 0, 2, 0): (0, -126.869898, 0),
+                ('Bell', 30, 1, 0):  (25.658906, -56.309932, 16.102114),
+                ('Bell', 30, 0, 1): (-48.590378, -40.893395, 49.106605),
+                ('Bell', 30, 0.5, c): (-25.658906, -56.309932, 43.897886)}
             new_elev, new_azim, new_roll = expectations[(style, roll, dx, dy)]
             np.testing.assert_allclose((ax.elev, ax.azim, ax.roll),
                                        (new_elev, new_azim, new_roll), atol=1e-6)