Speed up calculations for default tilt=0

scottshambaugh · scottshambaugh · commit 2e54be2ce86f · 2021-10-31T15:11:55.000-06:00
diff --git a/lib/mpl_toolkits/mplot3d/proj3d.py b/lib/mpl_toolkits/mplot3d/proj3d.py
@@ -55,7 +55,7 @@ def rotation_about_vector(v, angle):
     """
     Produce a rotation matrix for an angle in radians about a vector.
     """
-    v /= np.linalg.norm(v)
+    v = v/np.linalg.norm(v)
     s = np.sin(angle)
     c = np.cos(angle)
     t = 1-c
@@ -73,15 +73,16 @@ def view_transformation(E, R, V, tilt):
     n = n/np.linalg.norm(n)
     u = np.cross(V, n)
     u = u/np.linalg.norm(u)
-    v = np.cross(n, u)
-    v = v/np.linalg.norm(v)
+    v = np.cross(n, u)  # Will be a unit vector
 
-    Rtilt = rotation_about_vector(n, tilt)
-    u = np.dot(Rtilt, u)
-    v = np.dot(Rtilt, v)
+    # Save some computation for the default tilt=0
+    if tilt != 0:
+        Rtilt = rotation_about_vector(n, tilt)
+        u = np.dot(Rtilt, u)
+        v = np.dot(Rtilt, v)
 
-    Mr = np.diag([1.] * 4)
-    Mt = np.diag([1.] * 4)
+    Mr = np.eye(4)
+    Mt = np.eye(4)
     Mr[:3, :3] = [u, v, n]
     Mt[:3, -1] = -E
 
