Reorganized animations folder. Warning: While I tried to be systematic, there is a decent chance this will cause import errors somewhere.

animation/movement.py

@@ -0,0 +1,62 @@
+from __future__ import absolute_import
+
+from constants import *
+
+import warnings
+
+from animation.animation import Animation
+from utils.config_ops import digest_config
+
+class Homotopy(Animation):
+    CONFIG = {
+        "run_time" : 3,
+        "apply_function_kwargs" : {},
+    }
+    def __init__(self, homotopy, mobject, **kwargs):
+        """
+        Homotopy a function from (x, y, z, t) to (x', y', z')
+        """
+        def function_at_time_t(t):
+            return lambda p : homotopy(p[0], p[1], p[2], t)
+        self.function_at_time_t = function_at_time_t
+        digest_config(self, kwargs)
+        Animation.__init__(self, mobject, **kwargs)
+
+    def update_submobject(self, submob, start, alpha):
+        submob.points = start.points
+        submob.apply_function(
+            self.function_at_time_t(alpha),
+            **self.apply_function_kwargs
+        )
+
+class SmoothedVectorizedHomotopy(Homotopy):
+    def update_submobject(self, submob, start, alpha):
+        Homotopy.update_submobject(self, submob, start, alpha)
+        submob.make_smooth()
+
+class PhaseFlow(Animation):
+    CONFIG = {
+        "virtual_time" : 1,
+        "rate_func" : None,
+    }
+    def __init__(self, function, mobject, **kwargs):
+        digest_config(self, kwargs, locals())        
+        Animation.__init__(self, mobject, **kwargs)
+
+    def update_mobject(self, alpha):
+        if hasattr(self, "last_alpha"):
+            dt = self.virtual_time*(alpha-self.last_alpha)
+            self.mobject.apply_function(
+                lambda p : p + dt*self.function(p)
+            )
+        self.last_alpha = alpha
+
+class MoveAlongPath(Animation):
+    def __init__(self, mobject, path, **kwargs):
+        digest_config(self, kwargs, locals())
+        Animation.__init__(self, mobject, **kwargs)
+
+    def update_mobject(self, alpha):
+        point = self.path.point_from_proportion(alpha)
+        self.mobject.move_to(point)
+