Maybe 2/3 through inventing math project

animation/transform.py

@@ -9,11 +9,34 @@ from mobject import Mobject, Point
 from constants import *
 from helpers import *
 
+def straight_path(start_points, end_points, alpha):
+    return (1-alpha)*start_points + alpha*end_points
+
+def semi_circular_path(start_points, end_points, alpha, axis):
+    midpoints = (start_points + end_points) / 2
+    angle = alpha * np.pi
+    rot_matrix = rotation_matrix(angle, axis)[:2, :2]
+    result = np.zeros(start_points.shape)
+    result[:,:2] = np.dot(
+        (start_points - midpoints)[:,:2], 
+        np.transpose(rot_matrix)
+    ) + midpoints[:,:2]
+    result[:,2] = (1-alpha)*start_points[:,2] + alpha*end_points[:,2]
+    return result
+
+def clockwise_path(start_points, end_points, alpha):
+    return semi_circular_path(start_points, end_points, alpha, IN)
+
+def counterclockwise_path(start_points, end_points, alpha):
+    return semi_circular_path(start_points, end_points, alpha, OUT)
+
 class Transform(Animation):
     def __init__(self, mobject1, mobject2, 
                  run_time = DEFAULT_TRANSFORM_RUN_TIME,
+                 interpolation_function = straight_path,
                  black_out_extra_points = False,
                  *args, **kwargs):
+        self.interpolation_function = interpolation_function
         count1, count2 = mobject1.get_num_points(), mobject2.get_num_points()
         if count2 == 0:
             mobject2 = Point((SPACE_WIDTH, SPACE_HEIGHT, 0))
@@ -37,10 +60,14 @@ class Transform(Animation):
             self.non_redundant_m2_indices = indices
 
     def update_mobject(self, alpha):
-        Mobject.interpolate(
-            self.starting_mobject, 
-            self.ending_mobject,
-            self.mobject,
+        self.mobject.points = self.interpolation_function(
+            self.starting_mobject.points,
+            self.ending_mobject.points,
+            alpha
+        )
+        self.mobject.rgbs = straight_path(
+            self.starting_mobject.rgbs,
+            self.ending_mobject.rgbs,
             alpha
         )
 
@@ -59,23 +86,19 @@ class Transform(Animation):
                         )[self.non_redundant_m2_indices]
                     )
 
-class SemiCircleTransform(Transform):
-    def __init__(self, mobject1, mobject2, counterclockwise = True,
-                 *args, **kwargs):
-        Transform.__init__(self, mobject1, mobject2, *args, **kwargs)
-        self.axis = (0, 0, 1) if counterclockwise else (0, 0, -1)
+class ClockwiseTransform(Transform):
+    def __init__(self, mobject1, mobject2, **kwargs):
+        Transform.__init__(
+            self, mobject1, mobject2, 
+            interpolation_function = clockwise_path, **kwargs
+        )
 
-    def update_mobject(self, alpha):
-        sm, em = self.starting_mobject, self.ending_mobject
-        midpoints = (sm.points + em.points) / 2
-        angle = alpha * np.pi
-        rot_matrix = rotation_matrix(angle, self.axis)[:2, :2]
-        self.mobject.points[:,:2] = np.dot(
-            (sm.points - midpoints)[:,:2], 
-            np.transpose(rot_matrix)
-        ) + midpoints[:,:2]
-        self.mobject.points[:,2] = (1-alpha)*sm.points[:,2] + alpha*em.points[:,2]
-        self.mobject.rgbs = (1-alpha)*sm.rgbs + alpha*em.rgbs
+class CounterclockwiseTransform(Transform):
+    def __init__(self, mobject1, mobject2, **kwargs):
+        Transform.__init__(
+            self, mobject1, mobject2, 
+            interpolation_function = counterclockwise_path, **kwargs
+        )
 
 class FadeToColor(Transform):
     def __init__(self, mobject, color, *args, **kwargs):
@@ -119,12 +142,25 @@ class ApplyMethod(Transform):
         )
 
 class ApplyFunction(Transform):
-    def __init__(self, mobject, function, run_time = DEFAULT_ANIMATION_RUN_TIME,
-                 *args, **kwargs):
+    def __init__(self, function, mobject, **kwargs):
+        Transform.__init__(
+            self, 
+            mobject, 
+            function(copy.deepcopy(mobject)),
+            **kwargs
+        )
+        self.name = "ApplyFunctionTo"+str(mobject)
+
+
+class ApplyPointwiseFunction(Transform):
+    def __init__(self, mobject, function, 
+                 run_time = DEFAULT_ANIMATION_RUN_TIME, **kwargs):
         map_image = copy.deepcopy(mobject)
         map_image.points = np.array(map(function, map_image.points))
-        Transform.__init__(self, mobject, map_image, run_time = run_time, 
-                           *args, **kwargs)
+        Transform.__init__(
+            self, mobject, map_image, 
+            run_time = run_time, **kwargs
+        )
         self.name = "".join([
             "Apply",
             "".join([s.capitalize() for s in function.__name__.split("_")]),

constants.py

@@ -41,8 +41,8 @@ UP     = np.array(( 0, 1, 0))
 DOWN   = np.array(( 0,-1, 0))
 RIGHT  = np.array(( 1, 0, 0))
 LEFT   = np.array((-1, 0, 0))
-IN     = np.array(( 0, 0, 1))
-OUT    = np.array(( 0, 0,-1))
+IN     = np.array(( 0, 0,-1))
+OUT    = np.array(( 0, 0, 1))
 
 THIS_DIR  = os.path.dirname(os.path.realpath(__file__))
 FILE_DIR  = os.path.join(THIS_DIR, "files")
@@ -61,6 +61,7 @@ SIZE_TO_REPLACE = "SizeHere"
 TEX_TEXT_TO_REPLACE = "YourTextHere"
 TEMPLATE_TEX_FILE  = os.path.join(TEX_DIR, "template.tex")
 TEMPLATE_TEXT_FILE = os.path.join(TEX_DIR, "text_template.tex")
+MAX_LEN_FOR_HUGE_TEX_FONT = 25
 
 LOGO_PATH = os.path.join(IMAGE_DIR, "logo.png")
 

mobject/image_mobject.py

@@ -81,18 +81,26 @@ class VideoIcon(ImageMobject):
         self.scale(0.3)
         self.center()
 
-def text_mobject(text, size = "\\Large"):
+def text_mobject(text, size = None):
+    size = size or "\\Large" #TODO, auto-adjust?
     return tex_mobject(text, size, TEMPLATE_TEXT_FILE)
 
 def tex_mobject(expression, 
-                size = "\\Huge", 
+                size = None, 
                 template_tex_file = TEMPLATE_TEX_FILE):
+    if size == None:
+        if len("".join(expression)) < MAX_LEN_FOR_HUGE_TEX_FONT:
+            size = "\\Huge"
+        else:
+            size = "\\large"
+        #Todo, make this more sophisticated.
     images = tex_to_image(expression, size, template_tex_file)
     if isinstance(images, list):
         #TODO, is checking listiness really the best here?
-        return CompoundMobject(*map(ImageMobject, images)).center()
+        result = CompoundMobject(*map(ImageMobject, images))
     else:
-        return ImageMobject(images).center()
+        result = ImageMobject(images)
+    return result.highlight("white").center()
 
 
 

mobject/mobject.py

@@ -146,11 +146,15 @@ class Mobject(object):
         center = self.get_center()
         return self.center().scale(scale_factor).shift(center)
 
+    def stretch(self, factor, dim):
+        self.points[:,dim] *= factor
+        return self
+
     def stretch_to_fit(self, length, dim):
         center = self.get_center()
         old_length = max(self.points[:,dim]) - min(self.points[:,dim])
         self.center()
-        self.points[:,dim] *= length/old_length
+        self.stretch(length/old_length, dim)
         self.shift(center)
         return self
 
@@ -178,6 +182,9 @@ class Mobject(object):
         return self
 
     def replace(self, mobject, stretch = False):
+        if mobject.get_num_points() == 0:
+            raise Warning("Attempting to replace mobject with no points")
+            return self
         if stretch:
             self.stretch_to_fit_width(mobject.get_width())
             self.stretch_to_fit_height(mobject.get_height())
@@ -231,11 +238,34 @@ class Mobject(object):
     ### Getters ###
 
     def get_num_points(self):
-        return self.points.shape[0]
+        return len(self.points)
 
     def get_center(self):
+        return (np.max(self.points, 0) + np.min(self.points, 0))/2.0
+
+    def get_center_of_mass(self):
         return np.apply_along_axis(np.mean, 0, self.points)
 
+    def get_border_point(self, direction):
+        return self.points[np.argmax(np.dot(self.points, direction))]
+
+    def get_edge_center(self, dim, max_or_min_func):
+        result = self.get_center()
+        result[dim] = max_or_min_func(self.points[:,dim])
+        return result
+
+    def get_top(self):
+        return self.get_edge_center(1, np.max)
+
+    def get_bottom(self):
+        return self.get_edge_center(1, np.min)
+
+    def get_right(self):
+        return self.get_edge_center(0, np.max)
+
+    def get_left(self):
+        return self.get_edge_center(0, np.min)
+
     def get_width(self):
         return np.max(self.points[:, 0]) - np.min(self.points[:, 0])
 

mobject/simple_mobjects.py

@@ -6,6 +6,7 @@ from constants import *
 from helpers import *
 
 class Point(Mobject):
+    DEFAULT_COLOR = "black"
     def __init__(self, point = (0, 0, 0), *args, **kwargs):
         Mobject.__init__(self, *args, **kwargs)
         self.points = np.array(point).reshape(1, 3)
@@ -21,16 +22,18 @@ class Arrow(Mobject1D):
                  length = 1, 
                  tip_length = 0.25,
                  normal = (0, 0, 1), 
+                 density = DEFAULT_POINT_DENSITY_1D,
                  *args, **kwargs):
         self.point = np.array(point)
         if tail is not None:
             direction = self.point - tail
             length = np.linalg.norm(direction)
         self.direction = np.array(direction) / np.linalg.norm(direction)
+        density *= max(length, 0.1)
         self.length = length
         self.normal = np.array(normal)
         self.tip_length = tip_length
-        Mobject1D.__init__(self, *args, **kwargs)
+        Mobject1D.__init__(self, density = density, **kwargs)
 
     def generate_points(self):
         self.add_points([
@@ -131,12 +134,34 @@ class CurvedLine(Line):
 
 class Circle(Mobject1D):
     DEFAULT_COLOR = "red"
+    def __init__(self, radius = 1.0, **kwargs):
+        self.radius = radius
+        Mobject1D.__init__(self, **kwargs)
+
     def generate_points(self):
         self.add_points([
-            (np.cos(theta), np.sin(theta), 0)
-            for theta in np.arange(0, 2 * np.pi, self.epsilon)
+            (self.radius*np.cos(theta), self.radius*np.sin(theta), 0)
+            for theta in np.arange(0, 2 * np.pi, self.epsilon/self.radius)
         ])
 
+class Rectangle(Mobject1D):
+    DEFAULT_COLOR = "yellow"
+    def __init__(self, height = 2.0, width = 2.0, **kwargs):
+        self.height, self.width = height, width
+        Mobject1D.__init__(self, **kwargs)
+
+    def generate_points(self):
+        wh = [self.width/2.0, self.height/2.0]
+        self.add_points([
+            (x, u, 0) if dim==0 else (u, x, 0)
+            for dim in 0, 1
+            for u in wh[1-dim], -wh[1-dim]
+            for x in np.arange(-wh[dim], wh[dim], self.epsilon)
+        ])
+
+class Square(Rectangle):
+    def __init__(self, side_length = 2.0, **kwargs):
+        Rectangle.__init__(self, side_length, side_length, **kwargs)
 
 class Bubble(Mobject):
     def __init__(self, direction = LEFT, index_of_tip = -1, center = ORIGIN):
@@ -151,7 +176,7 @@ class Bubble(Mobject):
         return self.points[self.index_of_tip]
 
     def get_bubble_center(self):
-        return Mobject.get_center(self)+self.center_offset
+        return self.get_center()+self.center_offset
 
     def move_tip_to(self, point):
         self.shift(point - self.get_tip())
@@ -168,8 +193,7 @@ class Bubble(Mobject):
     def add_content(self, mobject):
         mobject.scale(0.75*self.get_width() / mobject.get_width())
         mobject.shift(self.get_bubble_center())
-        self.content = CompoundMobject(self.content, mobject)
-        self.add(self.content)
+        self.content = mobject
         return self
 
     def write(self, text):
@@ -177,10 +201,7 @@ class Bubble(Mobject):
         return self
 
     def clear(self):
-        num_content_points = self.content.points.shape[0]
-        self.points = self.points[:-num_content_points]
-        self.rgbs = self.rgbs[:-num_content_points]
-        self.contents = Mobject()
+        self.content = Mobject()
         return self
 
 class SpeechBubble(Bubble):

sample_script.py

@@ -10,14 +10,24 @@ from animation import *
 from mobject import *
 from constants import *
 from region import *
-from scene import Scene
+from scene import Scene, RearrangeEquation
 from script_wrapper import command_line_create_scene
 
 
-class SampleScene(Scene):
+class SampleScene(RearrangeEquation):
     def construct(self):
-        tauy = TauCreature()
-        self.animate(ApplyMethod(tauy.make_sad))
+        start_terms = "a + b = c".split(" ")
+        end_terms = "a = c - b + 0".split(" ")
+        index_map = {
+            0 : 0,
+            1 : 3,
+            2 : 4,
+            3 : 1,
+            4 : 2,
+        }
+        RearrangeEquation.construct(
+            self, start_terms, end_terms, index_map
+        )
 
 
 

scene/__init__.py

@@ -1,2 +1,3 @@
 from scene import *
 from sub_scenes import *
+from arithmetic_scenes import *

scene/arithmetic_scenes.py

@@ -0,0 +1,93 @@
+import numpy as np
+import itertools as it
+
+from scene import Scene
+from graphs import *
+
+from mobject import *
+from animation import *
+from region import *
+from constants import *
+from helpers import *
+
+class RearrangeEquation(Scene):
+    def construct(
+        self, 
+        start_terms, 
+        end_terms, 
+        index_map,
+        size = None,
+        path = counterclockwise_path,
+        start_transform = None,
+        end_transform = None,
+        leave_start_terms = False,
+        transform_kwargs = {},
+        ):
+        transform_kwargs["interpolation_function"] = path
+        start_mobs, end_mobs = self.get_mobs_from_terms(
+            start_terms, end_terms, size
+        )
+        if start_transform:
+            start_mobs = start_transform(CompoundMobject(*start_mobs)).split()
+        if end_transform:
+            end_mobs = end_transform(CompoundMobject(*end_mobs)).split()
+        unmatched_start_indices = set(range(len(start_mobs)))
+        unmatched_end_indices   = set(range(len(end_mobs)))
+        unmatched_start_indices.difference_update(
+            [n%len(start_mobs) for n in index_map]
+        )
+        unmatched_end_indices.difference_update(
+            [n%len(end_mobs) for n in index_map.values()]
+        )
+        mobject_pairs = [
+            (start_mobs[a], end_mobs[b])
+            for a, b in index_map.iteritems()
+        ]+ [
+            (Point(end_mobs[b].get_center()), end_mobs[b])
+            for b in unmatched_end_indices
+        ]
+        if not leave_start_terms:
+            mobject_pairs += [
+                (start_mobs[a], Point(start_mobs[a].get_center()))
+                for a in unmatched_start_indices
+            ] 
+
+        self.add(*start_mobs)
+        if leave_start_terms:
+            self.add(CompoundMobject(*start_mobs))
+        self.dither()
+        self.animate(*[
+            Transform(*pair, **transform_kwargs)
+            for pair in mobject_pairs
+        ])
+        self.dither()
+
+
+    def get_mobs_from_terms(self, start_terms, end_terms, size):
+        """
+        Need to ensure that all image mobjects for a tex expression
+        stemming from the same string are point-for-point copies of one
+        and other.  This makes transitions much smoother, and not look
+        like point-clouds.
+        """
+        num_start_terms = len(start_terms)
+        all_mobs = np.array(
+            tex_mobject(start_terms, size = size).split() + \
+            tex_mobject(end_terms, size = size).split()
+        )
+        all_terms = np.array(start_terms+end_terms)
+        for term in set(all_terms):
+            matches = all_terms == term
+            if sum(matches) > 1:
+                base_mob = all_mobs[list(all_terms).index(term)]
+                all_mobs[matches] = [
+                    deepcopy(base_mob).replace(target_mob)
+                    for target_mob in all_mobs[matches]
+                ]
+        return all_mobs[:num_start_terms], all_mobs[num_start_terms:]
+
+
+
+
+
+

scene/graphs.py

@@ -247,7 +247,7 @@ class GraphScene(Scene):
         mobject.center()
         diameter = max(mobject.get_height(), mobject.get_width())
         self.animate(*[
-            SemiCircleTransform(
+            CounterclockwiseTransform(
                 vertex,
                 deepcopy(mobject).shift(vertex.get_center())
             )

scene/scene.py

@@ -213,7 +213,6 @@ class Scene(object):
         self.number = num_mob
         return self
 
-
     def get_frame(self):
         frame = self.background
         for mob in self.mobjects:
@@ -224,6 +223,10 @@ class Scene(object):
         self.frames += [self.get_frame()]*int(duration / self.frame_duration)
         return self
 
+    def repeat(self, num):
+        self.frames = self.frames*num
+        return self
+
     def write_to_gif(self, name = None, 
                      end_dither_time = DEFAULT_DITHER_TIME):
         self.dither(end_dither_time)

scripts/ecf_graph_scenes.py

@@ -165,7 +165,7 @@ class OldIntroduceGraphs(GraphScene):
         friends = text_mobject("Friends").scale(EDGE_ANNOTATION_SCALE_VAL)
         self.annotate_edges(friends.shift((0, friends.get_height()/2, 0)))
         self.animate(*[
-            SemiCircleTransform(vertex, Dot(point))
+            CounterclockwiseTransform(vertex, Dot(point))
             for vertex, point in zip(self.vertices, self.points)
         ]+[
             Transform(ann, line)
@@ -558,7 +558,7 @@ class FacebookGraph(GraphScene):
         self.annotate_edges(friends)
         self.dither()
         self.animate(*[
-            SemiCircleTransform(account, vertex)
+            CounterclockwiseTransform(account, vertex)
             for account, vertex in zip(accounts, self.vertices)
         ])
         self.dither()
@@ -1176,7 +1176,7 @@ class FinalSum(Scene):
             copy = plus if index == -2 else deepcopy(mob)
             copy.center().shift(lines[index].get_center())
             copy.scale_in_place(lines[index].get_width()/mob.get_width())
-            anims.append(SemiCircleTransform(copy, mob))
+            anims.append(CounterclockwiseTransform(copy, mob))
         self.clear()
         self.animate(*anims, run_time = 2.0)
         self.dither()

scripts/moser_main.py

@@ -226,7 +226,7 @@ class HardProblemsSimplerQuestions(Scene):
         self.remove(*self.mobjects)
         self.add(fermat["n"])
         self.animate(*[
-            SemiCircleTransform(mobs[0], mobs[1])
+            CounterclockwiseTransform(mobs[0], mobs[1])
             for f_copy, sym in zip(copies, ["3", "2"])            
             for mobs in zip(f_copy.split(), fermat[sym].split())
         ])
@@ -260,7 +260,7 @@ class HardProblemsSimplerQuestions(Scene):
         self.animate(
             FadeIn(fermat2_jargon),
             FadeIn(fermat3_jargon),
-            SemiCircleTransform(start_line, end_line),
+            CounterclockwiseTransform(start_line, end_line),
             ShowCreation(dots)
         )
         self.dither()
@@ -686,17 +686,17 @@ class GraphsAndEulersFormulaJoke(Scene):
         self.add(axes)
         self.animate(ShowCreation(graph), run_time = 1.0)
         eulers = tex_mobject("e^{\pi i} = -1").shift((0, 3, 0))
-        self.animate(SemiCircleTransform(
+        self.animate(CounterclockwiseTransform(
             deepcopy(graph), eulers
         ))
         self.dither()
         self.remove(*self.mobjects)
         self.add(eulers)
-        self.animate(SemiCircleTransform(
+        self.animate(CounterclockwiseTransform(
             CompoundMobject(axes, graph),
             Point((-SPACE_WIDTH, SPACE_HEIGHT, 0))
         ))
-        self.animate(SemiCircleTransform(
+        self.animate(CounterclockwiseTransform(
             eulers,
             Point((SPACE_WIDTH, SPACE_HEIGHT, 0))
         ))
@@ -899,7 +899,7 @@ class ShowMoserGraphLines(CircleScene):
             compound = CompoundMobject(*mobs)            
             if mobs in (self.dots, self.intersection_dots):
                 self.remove(*mobs)
-                self.animate(SemiCircleTransform(
+                self.animate(CounterclockwiseTransform(
                     compound,
                     deepcopy(compound).scale(1.05),
                     alpha_func = there_and_back,
@@ -1055,7 +1055,7 @@ class ApplyEulerToMoser(CircleScene):
                 )
 
         self.animate(*[
-            SemiCircleTransform(d[1], d[2], run_time = 2.0)
+            CounterclockwiseTransform(d[1], d[2], run_time = 2.0)
             for d in [V, minus, E, plus, F, equals, two]
         ])
         self.dither()
@@ -1164,8 +1164,8 @@ class ApplyEulerToMoser(CircleScene):
         self.dither()
         self.remove(*self.mobjects)
         self.animate(
-            SemiCircleTransform(two[6], two[7]),
-            SemiCircleTransform(plus[6], plus[7]),
+            CounterclockwiseTransform(two[6], two[7]),
+            CounterclockwiseTransform(plus[6], plus[7]),
             *[
                 Transform(d[6], d[7])
                 for d in [F, equals, nc2, plus1, nc4]
@@ -1184,7 +1184,7 @@ class ApplyEulerToMoser(CircleScene):
         one = tex_mobject("1").shift(two.get_center())
         two.highlight("red")
         self.add(two)
-        self.animate(SemiCircleTransform(two, one))
+        self.animate(CounterclockwiseTransform(two, one))
 
 class FormulaRelatesToPowersOfTwo(Scene):
     def __init__(self, *args, **kwargs):
@@ -1226,7 +1226,7 @@ class FormulaRelatesToPowersOfTwo(Scene):
         self.remove(*self.mobjects)
         self.add(*forms + sums + results)
         self.animate(*[
-            SemiCircleTransform(result, pof2)
+            CounterclockwiseTransform(result, pof2)
             for result, pof2 in zip(results, powers_of_two)
         ])        
 
@@ -1277,7 +1277,7 @@ class PascalsTriangleWithNChooseK(PascalsTriangleScene):
             self.dither()
             self.remove(*self.mobjects)
             self.animate(*[
-                SemiCircleTransform(
+                CounterclockwiseTransform(
                     deepcopy(mob_dicts[i][n][k]), 
                     mob_dicts[1-i][n][k]
                 )
@@ -1399,7 +1399,7 @@ class PascalsTriangleSumRows(PascalsTriangleScene):
         self.remove(*to_remove)
         self.add(*powers_of_two)
         for n in range(self.nrows):
-            self.animate(SemiCircleTransform(
+            self.animate(CounterclockwiseTransform(
                 powers_of_two[n], powers_of_two_symbols[n], 
                 run_time = run_time
             ))
@@ -1456,14 +1456,14 @@ class MoserSolutionInPascal(PascalsTriangleScene):
         ])
         self.animate(*
             [
-                SemiCircleTransform(
+                CounterclockwiseTransform(
                     self.coords_to_n_choose_k[n0][k0],
                     self.coords_to_mobs[n0][k0]
                 )
                 for n0, k0 in self.coords
                 if (n0, k0) not in [(n, k) for k in term_range]
             ]+[
-                SemiCircleTransform(terms[k], target_terms[k])
+                CounterclockwiseTransform(terms[k], target_terms[k])
                 for k in term_range
             ]
         )
@@ -1565,7 +1565,7 @@ class ExplainNChoose2Formula(Scene):
         b_mob = nums.pop(b-2 if a < b else b-1)
         self.add(b_mob)
         self.animate(*[
-            SemiCircleTransform(
+            CounterclockwiseTransform(
                 mob, 
                 Point(mob.get_center()).highlight("black")
             )
@@ -1582,8 +1582,8 @@ class ExplainNChoose2Formula(Scene):
         b_copy = deepcopy(b_mob).center().shift(a_center - (0, 2, 0))
         self.add(over_2, deepcopy(a_mob), deepcopy(b_mob))
         self.animate(
-            SemiCircleTransform(a_mob, a_copy),
-            SemiCircleTransform(b_mob, b_copy),
+            CounterclockwiseTransform(a_mob, a_copy),
+            CounterclockwiseTransform(b_mob, b_copy),
             FadeIn(parens_copy),
             FadeIn(text_mobject("is considered the same as"))
         )
@@ -1635,7 +1635,7 @@ class ExplainNChoose4Formula(Scene):
                 )
             else:
                 self.animate(*[
-                    SemiCircleTransform(
+                    CounterclockwiseTransform(
                         mob, 
                         Point(mob.get_center()).highlight("black")
                     )
@@ -1658,7 +1658,7 @@ class ExplainNChoose4Formula(Scene):
                 for i in range(4)
             ]
             compound_quad = CompoundMobject(*quad_mobs)
-            self.animate(SemiCircleTransform(
+            self.animate(CounterclockwiseTransform(
                 compound_quad,
                 CompoundMobject(*new_quad_mobs)
             ))

scripts/tau_poem.py

@@ -203,12 +203,12 @@ class TauPoem(Scene):
         )
         self.add(two_pi)
         self.dither()
-        self.animate(SemiCircleTransform(
+        self.animate(CounterclockwiseTransform(
             two_pi, sphere,
             alpha_func = lambda t : 2*high_inflection_0_to_1(t/2)
         ))
         self.remove(two_pi)
-        self.animate(SemiCircleTransform(
+        self.animate(CounterclockwiseTransform(
             sphere, tau,
             alpha_func = lambda t : 2*(high_inflection_0_to_1(t/2+0.5)-0.5)
         ))
@@ -302,10 +302,10 @@ class TauPoem(Scene):
         self.dither()
         self.remove(bubble)
         bubble_copy = deepcopy(bubble)
-        self.animate(SemiCircleTransform(bubble_copy, heart))
+        self.animate(CounterclockwiseTransform(bubble_copy, heart))
         self.dither()
         self.remove(bubble_copy)
-        self.animate(SemiCircleTransform(heart, bubble))
+        self.animate(CounterclockwiseTransform(heart, bubble))
         self.dither()
 
 
@@ -323,7 +323,7 @@ class TauPoem(Scene):
                 Point(pi.right_leg.points[0,:]).highlight("black")
             ),
             Transform(pi.mouth, tau.mouth),
-            SemiCircleTransform(
+            CounterclockwiseTransform(
                 two, 
                 Dot(two.get_center()).highlight("black")
             )
@@ -412,8 +412,8 @@ class TauPoem(Scene):
             ShowCreation(circle)
         )
         self.animate(
-            SemiCircleTransform(sine_period, tau_line),
-            SemiCircleTransform(circle, deepcopy(tau_line)),
+            CounterclockwiseTransform(sine_period, tau_line),
+            CounterclockwiseTransform(circle, deepcopy(tau_line)),
             FadeOut(axes),
             FadeOut(grid),
             FadeOut(sine),
@@ -435,7 +435,7 @@ class TauPoem(Scene):
 
         self.add(*formula)
         self.dither()
-        self.animate(SemiCircleTransform(two_pi, tau))
+        self.animate(CounterclockwiseTransform(two_pi, tau))
         self.remove(two_pi)
         self.animate(BlinkPiCreature(tau))
         self.dither()