First page of chapter 5

eola/chapter5.py

@@ -0,0 +1,355 @@
+from mobject.tex_mobject import TexMobject
+from mobject import Mobject
+from mobject.image_mobject import ImageMobject
+from mobject.vectorized_mobject import VMobject
+
+from animation.animation import Animation
+from animation.transform import *
+from animation.simple_animations import *
+from topics.geometry import *
+from topics.characters import *
+from topics.functions import *
+from topics.number_line import *
+from topics.numerals import *
+from scene import Scene
+from camera import Camera
+from mobject.svg_mobject import *
+from mobject.tex_mobject import *
+from mobject.vectorized_mobject import *
+
+from eola.matrix import *
+from eola.two_d_space import *
+from eola.chapter3 import MatrixVectorMultiplicationAbstract
+
+class Blob(Circle):
+    CONFIG = {
+        "stroke_color" : TEAL,
+        "fill_color" : BLUE_E,
+        "fill_opacity" : 1,
+        "random_seed" : 1,
+        "random_nudge_size" : 0.5,
+        "height" : 2,
+    }
+    def __init__(self, **kwargs):
+        Circle.__init__(self, **kwargs)
+        random.seed(self.random_seed)
+        self.apply_complex_function(
+            lambda z : z*(1+self.random_nudge_size*(random.random()-0.5))
+        )
+        self.scale_to_fit_height(self.height).center()
+
+    def probably_contains(self, point):
+        border_points = np.array(self.get_anchors_and_handles()[0])
+        distances = map(lambda p : np.linalg.norm(p-point), border_points)
+        min3 = border_points[np.argsort(distances)[:3]]
+        center_direction = self.get_center() - point
+        in_center_direction = map(
+            lambda p : np.dot(p-point, center_direction) > 0, 
+            min3
+        )
+        return sum(in_center_direction) <= 2
+            
+
+class OpeningQuote(Scene):
+    def construct(self):
+        words = TextMobject([
+            "``The purpose of computation is \\\\",
+            "insight",
+            ", not ",
+            "numbers.",
+            "''",
+        ], separate_list_arg_with_spaces = False)
+        # words.scale_to_fit_width(2*SPACE_WIDTH - 2)
+        words.to_edge(UP)
+        words.split()[1].highlight(BLUE)
+        words.split()[3].highlight(GREEN)
+        author = TextMobject("-Richard Hamming")
+        author.highlight(YELLOW)
+        author.next_to(words, DOWN, buff = 0.5)
+
+        self.play(FadeIn(words))
+        self.dither(2)
+        self.play(Write(author, run_time = 3))
+        self.dither()
+
+class MovingForward(TeacherStudentsScene):
+    def construct(self):
+        self.setup()
+        student = self.get_students()[1]
+        bubble = student.get_bubble(direction = RIGHT, width = 5)
+        bubble.rotate(-np.pi/12)
+        bubble.next_to(student, UP, aligned_edge = RIGHT)
+        bubble.shift(0.5*LEFT)
+        bubble.make_green_screen()
+
+        self.teacher_says("""
+            Y'all know about linear
+            transformations, right?
+        """, width = 7)
+        self.play(
+            ShowCreation(bubble),
+            student.change_mode, "pondering"
+        )
+        self.dither(2)
+
+class StretchingTransformation(LinearTransformationScene):
+    def construct(self):
+        self.setup()
+        self.add_title("Generally stretches space")
+        self.apply_transposed_matrix([[3, 1], [-1, 2]])
+        self.dither()
+
+class SquishingTransformation(LinearTransformationScene):
+    CONFIG = {
+        "foreground_plane_kwargs" : {
+            "x_radius" : 3*SPACE_WIDTH,
+            "y_radius" : 3*SPACE_WIDTH,
+            "secondary_line_ratio" : 0
+        },
+    }
+    def construct(self):
+        self.setup()
+        self.add_title("Generally squishes space")
+        self.apply_transposed_matrix([[1./2, -0.5], [1, 1./3]])
+        self.dither()
+
+class AskAboutStretching(LinearTransformationScene):
+    def construct(self):
+        self.setup()
+        words = TextMobject("""
+            Exactly how much are 
+            things being stretched?
+        """)
+        words.add_background_rectangle()
+        words.to_corner(UP+RIGHT)
+        words.highlight(YELLOW)
+        self.apply_transposed_matrix(
+            [[2, 1], [-1, 3]],
+            added_anims = [Write(words)]
+        )
+        self.dither()
+
+class AskAboutStretchingSpecifically(LinearTransformationScene):
+    def construct(self):
+        self.setup()
+        self.add_title(["How much are", "areas", "scaled?"])
+        hma, areas, scaled = self.title.split()[1].split()
+        areas.highlight(YELLOW)
+        blob = Blob().shift(UP+RIGHT)
+
+        label = TextMobject("Area")
+        label.highlight(YELLOW)
+        label = VMobject(VectorizedPoint(label.get_left()), label)
+        label.move_to(blob)
+        target_label = TexMobject(["c \\cdot", "\\text{Area}"])
+        target_label.split()[1].highlight(YELLOW)
+
+        self.add_transformable_mobject(blob)
+        self.add_moving_mobject(label, target_label)
+        self.dither()
+        self.apply_transposed_matrix([[2, -1], [1, 1]])
+        arrow = Arrow(scaled, label.target.split()[0])
+        self.play(ShowCreation(arrow))
+        self.dither()
+
+class BeautyNowUsesLater(TeacherStudentsScene):
+    def construct(self):
+        self.setup()
+        self.teacher_says("Beauty now, uses later")
+        self.dither()
+
+class DiagonalExample(LinearTransformationScene):
+    CONFIG = {
+        "show_square" : False, 
+        "show_coordinates" : True,
+        "transposed_matrix" : [[3, 0], [0, 2]]
+    }
+    def construct(self):
+        self.setup()
+        matrix = Matrix(np.array(self.transposed_matrix).transpose())
+        matrix.highlight_columns(X_COLOR, Y_COLOR)
+        matrix.next_to(ORIGIN, LEFT).to_edge(UP)
+        matrix_background = BackgroundRectangle(matrix)
+        self.play(ShowCreation(matrix_background), Write(matrix))
+        if self.show_square:
+            self.add_unit_square(animate = True)
+        self.add_foreground_mobject(matrix_background, matrix)
+        self.dither()
+        self.apply_transposed_matrix([self.transposed_matrix[0], [0, 1]])
+        self.apply_transposed_matrix([[1, 0], self.transposed_matrix[1]])
+        self.dither()
+        if self.show_square:
+
+
+            bottom_brace = Brace(self.i_hat, DOWN)
+            right_brace = Brace(self.square, RIGHT)
+            width = TexMobject(str(self.transposed_matrix[0][0]))
+            height = TexMobject(str(self.transposed_matrix[1][1]))
+            width.next_to(bottom_brace, DOWN)
+            height.next_to(right_brace, RIGHT)
+            for mob in bottom_brace, width, right_brace, height:
+                mob.add_background_rectangle()
+                self.play(Write(mob, run_time = 0.5))
+            self.dither()
+
+            width_target, height_target = width.copy(), height.copy()
+            det = np.linalg.det(self.transposed_matrix)
+            times, eq_det = map(TexMobject, ["\\times", "=%d"%det])
+            words = TextMobject("New area $=$")
+            equation = VMobject(
+                words, width_target, times, height_target, eq_det
+            )
+            equation.arrange_submobjects(RIGHT, buff = 0.2)
+            equation.next_to(self.square, UP, aligned_edge = LEFT)
+            equation.shift(0.5*RIGHT)
+            background_rect = BackgroundRectangle(equation)
+
+            self.play(
+                ShowCreation(background_rect),                
+                Transform(width.copy(), width_target),
+                Transform(height.copy(), height_target),
+                *map(Write, [words, times, eq_det])
+            )
+            self.dither()
+
+class DiagonalExampleWithSquare(DiagonalExample):
+    CONFIG = {
+        "show_square" : True
+    }
+
+class ShearExample(DiagonalExample):
+    CONFIG = {
+        "show_square" : False, 
+        "show_coordinates" : True,
+        "transposed_matrix" : [[1, 0], [1, 1]]
+    }
+
+class ShearExampleWithSquare(DiagonalExample):
+    CONFIG = {
+        "show_square" : True, 
+        "show_coordinates" : True,
+        "show_coordinates" : False,
+        "transposed_matrix" : [[1, 0], [1, 1]]
+    }
+
+class ThisSquareTellsEverything(LinearTransformationScene):
+    def construct(self):
+        self.setup()
+        self.add_unit_square()
+        words = TextMobject("""
+            This square gives you
+            everything you need.
+        """)
+        words.to_corner(UP+RIGHT)
+        words.highlight(YELLOW)
+        words.add_background_rectangle()
+        arrow = Arrow(
+            words.get_bottom(), self.square.get_right(), 
+            color = WHITE
+        )
+
+        self.play(Write(words, run_time = 2))
+        self.play(ShowCreation(arrow))
+        self.add_foreground_mobject(words, arrow)
+        self.dither()
+        self.apply_transposed_matrix([[1.5, -0.5], [1, 1.5]])
+        self.dither()
+
+class WhatHappensToOneSquareHappensToAll(LinearTransformationScene):
+    def construct(self):
+        self.setup()
+        self.add_unit_square()
+        pairs = [
+            (2*RIGHT+UP, 1),
+            (3*LEFT, 2),
+            (2*LEFT+DOWN, 0.5),          
+            (3.5*RIGHT+2.5*UP, 1.5),
+            (RIGHT+2*DOWN, 0.25),
+            (3*LEFT+3*DOWN, 1),
+        ]
+        squares = VMobject()
+        for position, side_length in pairs:
+            square = self.square.copy()
+            square.scale(side_length)
+            square.shift(position)
+            squares.add(square)
+        self.play(FadeIn(
+            squares, submobject_mode = "lagged_start",
+            run_time = 3
+        ))
+        self.add_transformable_mobject(squares)
+        self.apply_transposed_matrix([[1, -1], [0.5, 1]])
+        self.dither()
+
+class BreakBlobIntoGridSquares(LinearTransformationScene):
+    CONFIG = {
+        "square_size" : 0.5,
+        "blob_height" : 3,
+    }
+    def construct(self):
+        self.setup()
+        blob = Blob(
+            height = self.blob_height, 
+            random_seed = 5,
+            random_nudge_size = 0.2,
+        )
+        blob.next_to(ORIGIN, UP+RIGHT)
+        self.add_transformable_mobject(blob)
+        arange = np.arange(
+            0, self.blob_height + self.square_size, 
+            self.square_size
+        )
+        square = Square(side_length = self.square_size)
+        square.set_stroke(YELLOW, width = 2)
+        square.set_fill(YELLOW, opacity = 0.3)
+        squares = VMobject()
+        for x, y in it.product(*[arange]*2):
+            point = x*RIGHT + y*UP
+            if blob.probably_contains(point):
+                squares.add(square.copy().shift(point))
+        self.play(ShowCreation(
+            squares, submobject_mode = "lagged_start",
+            run_time = 2,
+        ))
+        self.add_transformable_mobject(squares)
+        self.dither()
+        self.apply_transposed_matrix([[1, -1], [0.5, 1]])
+        self.dither()
+
+class BreakBlobIntoGridSquaresGranular(BreakBlobIntoGridSquares):
+    CONFIG = {
+        "square_size" : 0.25
+    }
+
+class BreakBlobIntoGridSquaresVeryGranular(BreakBlobIntoGridSquares):
+    CONFIG = {
+        "square_size" : 0.1
+    }
+
+class NameDeterminant(LinearTransformationScene):
+    CONFIG = {
+        "t_matrix" : [[1, 0], [2, 1]]
+    }
+    def construct(self):
+        self.setup()
+        self.add_unit_square()
+        self.add_title(["The", "``determinant''", "of a transformation"])
+        self.title.split()[1].split()[1].highlight(YELLOW)
+
+        text = TextMobject("Area $=1$")
+        text.move_to(self.square)
+        det = np.linalg.det(self.t_matrix)
+        self.add_moving_mobject(text, TextMobject("Area $=%d$"%det))
+        self.show_frame()
+
+
+
+
+
+
+
+
+
+
+
+

eola/two_d_space.py

@@ -9,7 +9,8 @@ from animation.transform import ApplyPointwiseFunction, Transform, \
     ApplyMethod, FadeOut, ApplyFunction
 from animation.simple_animations import ShowCreation, Write
 from topics.number_line import NumberPlane, Axes
-from topics.geometry import Vector, Line, Circle, Arrow, Dot, BackgroundRectangle
+from topics.geometry import Vector, Line, Circle, Arrow, Dot, \
+    BackgroundRectangle, Square
 
 from helpers import *
 from eola.matrix import Matrix, VECTOR_LABEL_SCALE_VAL, vector_coordinate_label
@@ -260,8 +261,9 @@ class LinearTransformationScene(VectorScene):
         self.background_mobjects = []
         self.foreground_mobjects = []        
         self.transformable_mobjects = []
-        self.moving_vectors = []
+        self.moving_vectors = []        
         self.transformable_labels = []
+        self.moving_mobjects = []
 
 
         self.background_plane = NumberPlane(
@@ -301,6 +303,24 @@ class LinearTransformationScene(VectorScene):
     def add_transformable_mobject(self, *mobjects):
         self.add_special_mobjects(self.transformable_mobjects, *mobjects)
 
+    def add_moving_mobject(self, mobject, target_mobject = None):
+        mobject.target = target_mobject
+        self.add_special_mobjects(self.moving_mobjects, mobject)
+
+    def add_unit_square(self, color = YELLOW, opacity = 0.3, animate = False):
+        square = Square(color = color, side_length = 1)
+        square.shift(-square.get_corner(DOWN+LEFT))
+        if animate:
+            added_anims = map(Animation, self.moving_vectors)
+            self.play(ShowCreation(square), *added_anims)
+            self.play(square.set_fill, color, opacity, *added_anims)
+        else:
+            square.set_fill(color, opacity)
+        self.add_transformable_mobject(square)
+        self.bring_to_front(*self.moving_vectors)        
+        self.square = square
+        return self
+
     def add_vector(self, vector, color = YELLOW, **kwargs):
         vector = VectorScene.add_vector(
             self, vector, color = color, **kwargs
@@ -334,6 +354,7 @@ class LinearTransformationScene(VectorScene):
         if animate:
             self.play(Write(title))
         self.add_foreground_mobject(title)
+        self.title = title
         return self
 
     def get_matrix_transformation(self, transposed_matrix):
@@ -353,6 +374,14 @@ class LinearTransformationScene(VectorScene):
             self.add(start.copy().fade(0.7))
         return Transform(start, target, submobject_mode = "all_at_once")
 
+    def get_moving_mobject_movement(self, func):
+        for m in self.moving_mobjects:
+            if m.target is None:
+                m.target = m.copy()
+            target_point = func(m.get_center())
+            m.target.move_to(target_point)
+        return self.get_piece_movement(self.moving_mobjects)
+
     def get_vector_movement(self, func):
         for v in self.moving_vectors:
             v.target = Vector(func(v.get_end()), color = v.get_color())
@@ -382,13 +411,18 @@ class LinearTransformationScene(VectorScene):
     def apply_function(self, function, added_anims = [], **kwargs):
         if "run_time" not in kwargs:
             kwargs["run_time"] = 3
-        added_anims.append(self.get_vector_movement(function))
-        added_anims.append(self.get_transformable_label_movement())
-        added_anims += map(Animation, self.foreground_mobjects)
-        function_application = ApplyPointwiseFunction(
-            function, VMobject(*self.transformable_mobjects)
-        )
-        self.play(function_application, *added_anims, **kwargs)
+        anims = [
+            ApplyPointwiseFunction(function, t_mob)
+            for t_mob in self.transformable_mobjects
+        ] + [
+            self.get_vector_movement(function),
+            self.get_transformable_label_movement(),
+            self.get_moving_mobject_movement(function),
+        ] + [
+            Animation(f_mob)
+            for f_mob in self.foreground_mobjects
+        ] + added_anims
+        self.play(*anims, **kwargs)
 
 
 

extract_scene.py

@@ -122,7 +122,8 @@ def is_scene(obj):
 
 def prompt_user_for_choice(name_to_obj):
    num_to_name = {}
-   for count, name in zip(it.count(1), name_to_obj):
+   names = sorted(name_to_obj.keys())
+   for count, name in zip(it.count(1), names):
       print "%d: %s"%(count, name)
       num_to_name[count] = name
    try:

mobject/mobject.py

@@ -224,12 +224,12 @@ class Mobject(object):
         self.shift(target_point - point_to_align + buff*direction)
         return self
 
-    def shift_onto_screen(self):
+    def shift_onto_screen(self, **kwargs):
         space_lengths = [SPACE_WIDTH, SPACE_HEIGHT]
         for vect in UP, DOWN, LEFT, RIGHT:
             dim = np.argmax(np.abs(vect))
             if abs(self.get_edge_center(vect)[dim]) > space_lengths[dim]:
-                self.to_edge(vect)
+                self.to_edge(vect, **kwargs)
 
     def stretch_to_fit(self, length, dim, stretch = True):
         old_length = self.length_over_dim(dim)

mobject/vectorized_mobject.py

@@ -14,6 +14,7 @@ class VMobject(Mobject):
         "is_subpath"       : False,
         "close_new_points" : False,
         "mark_paths_closed" : False,
+        "considered_smooth" : True,
         "propogate_style_to_family" : False,
     }
     def __init__(self, *args, **kwargs):
@@ -181,6 +182,7 @@ class VMobject(Mobject):
         return self
 
     def make_smooth(self):
+        self.considered_smooth = True
         return self.change_anchor_mode("smooth")
 
     def make_jagged(self):
@@ -211,7 +213,7 @@ class VMobject(Mobject):
 
     def apply_function(self, function, maintain_smoothness = True):
         Mobject.apply_function(self, function)
-        if maintain_smoothness:
+        if maintain_smoothness and self.considered_smooth:
             self.make_smooth()
         return self
 

scene/scene.py

@@ -114,13 +114,13 @@ class Scene(object):
         )
         return self
 
-    def bring_to_front(self, mobject):
-        self.add(mobject)
+    def bring_to_front(self, *mobjects):
+        self.add(*mobjects)
         return self
 
-    def bring_to_back(self, mobject):
-        self.remove(mobject)
-        self.mobjects = [mobject] + self.mobjects
+    def bring_to_back(self, *mobjects):
+        self.remove(*mobjects)
+        self.mobjects = mobjects + self.mobjects
         return self
 
     def clear(self):

topics/characters.py

@@ -189,6 +189,7 @@ class Bubble(SVGMobject):
         self.stretch_to_fit_width(self.width)
         if self.direction[0] > 0:
             Mobject.flip(self)
+        self.direction_was_specified = ("direction" in kwargs)
         self.content = Mobject()
 
     def get_tip(self):
@@ -207,9 +208,11 @@ class Bubble(SVGMobject):
         self.direction = -np.array(self.direction)
         return self
 
-    def pin_to(self, mobject, allow_flipping = True):
+    def pin_to(self, mobject):
         mob_center = mobject.get_center()
-        if np.sign(mob_center[0]) != np.sign(self.direction[0]) and allow_flipping:
+        want_to_filp = np.sign(mob_center[0]) != np.sign(self.direction[0])
+        can_flip = not self.direction_was_specified
+        if want_to_filp and can_flip:
             self.flip()
         boundary_point = mobject.get_critical_point(UP-self.direction)
         vector_from_center = 1.0*(boundary_point-mob_center)

topics/geometry.py

@@ -56,6 +56,7 @@ class Dot(Circle): #Use 1D density, even though 2D
 class Line(VMobject):
     CONFIG = {
         "buff" : 0,
+        "considered_smooth" : False,
     }
     def __init__(self, start, end, **kwargs):
         digest_config(self, kwargs)
@@ -214,6 +215,7 @@ class Polygon(VMobject):
         "color" : GREEN_D,
         "mark_paths_closed" : True,
         "close_new_points" : True,
+        "considered_smooth" : False,
     }
     def __init__(self, *vertices, **kwargs):
         assert len(vertices) > 1
@@ -244,6 +246,7 @@ class Rectangle(VMobject):
         "width"  : 4.0,
         "mark_paths_closed" : True,
         "close_new_points" : True,
+        "considered_smooth" : False,
     }
     def generate_points(self):
         y, x = self.height/2., self.width/2.
@@ -302,6 +305,7 @@ class Grid(VMobject):
     CONFIG = {
         "height" : 6.0,
         "width"  : 6.0,
+        "considered_smooth" : False,
     }
     def __init__(self, rows, columns, **kwargs):
         digest_config(self, kwargs, locals())