Sure, I *could* separate all these updates into separate reasonable commits, but where's the fun in that?

animation/transform.py

@@ -9,6 +9,7 @@ from helpers import *
 from animation import Animation
 from simple_animations import DelayByOrder
 from mobject import Mobject, Point, VMobject, Group
+from topics.geometry import Dot
 
 class Transform(Animation):
     CONFIG = {
@@ -160,6 +161,26 @@ class ShimmerIn(DelayByOrder):
         mobject.sort_points(lambda p : np.dot(p, DOWN+RIGHT))
         DelayByOrder.__init__(self, FadeIn(mobject, **kwargs))
 
+class FocusOn(Transform):
+    CONFIG = {
+        "opacity" : 0.2,
+        "color" : GREY,
+        "run_time" : 2,
+        "remover" : True,
+    }
+    def __init__(self, mobject_or_point, **kwargs):
+        digest_config(self, kwargs)
+        big_dot = Dot(
+            radius = SPACE_WIDTH+SPACE_HEIGHT,
+            stroke_width = 0,
+            fill_color = self.color,
+            fill_opacity = 0,
+        )
+        little_dot = Dot(radius = 0)
+        little_dot.set_fill(self.color, opacity = self.opacity)
+        little_dot.move_to(mobject_or_point)
+
+        Transform.__init__(self, big_dot, little_dot, **kwargs)
 
 class Rotate(ApplyMethod):
     CONFIG = {

eoc/graph_scene.py

@@ -37,10 +37,7 @@ class GraphScene(Scene):
     def setup_axes(self, animate = False):
         x_num_range = float(self.x_max - self.x_min)
         self.space_unit_to_x = self.x_axis_width/x_num_range
-        if self.x_labeled_nums is None:
+        self.x_labeled_nums = self.x_labeled_nums or []
-            self.x_labeled_nums = np.arange(
-                self.x_min, self.x_max, 2*self.x_tick_frequency
-            )
         x_axis = NumberLine(
             x_min = self.x_min,
             x_max = self.x_max,
@@ -67,10 +64,7 @@ class GraphScene(Scene):
 
         y_num_range = float(self.y_max - self.y_min)
         self.space_unit_to_y = self.y_axis_height/y_num_range
-        if self.y_labeled_nums is None:
+        self.y_labeled_nums = self.y_labeled_nums or []
-            self.y_labeled_nums = np.arange(
-                self.y_min, self.y_max, 2*self.y_tick_frequency
-            )
         y_axis = NumberLine(
             x_min = self.y_min,
             x_max = self.y_max,
@@ -223,6 +217,20 @@ class GraphScene(Scene):
             **line_kwargs
         )  
 
+    def get_vertical_lines_to_graph(
+        self, graph,
+        x_min = None,
+        x_max = None,
+        num_lines = 20,
+        **kwargs
+        ):
+        x_min = x_min or self.x_min
+        x_max = x_max or self.x_max
+        return VGroup(*[
+            self.get_vertical_line_to_graph(x, graph, **kwargs)
+            for x in np.linspace(x_min, x_max, num_lines)
+        ])
+
     def get_secant_slope_group(
         self, 
         x, graph, 
@@ -236,6 +244,15 @@ class GraphScene(Scene):
         secant_line_color = None,
         secant_line_length = 10,
         ):
+        """
+        Resulting group is of the form VGroup(
+            dx_line, 
+            df_line,
+            dx_label, (if applicable)
+            df_label, (if applicable)
+            secant_line, (if applicable)
+        )
+        """
         kwargs = locals()
         kwargs.pop("self")
         group = VGroup()

mobject/mobject.py

@@ -310,7 +310,7 @@ class Mobject(object):
     def scale_to_fit_height(self, height):
         return self.stretch_to_fit(height, 1, stretch = False)
 
-    def space_out_submobjects(self, factor = 1.5):
+    def space_out_submobjects(self, factor = 1.5, **kwargs):
         self.scale_in_place(factor)
         for submob in self.submobjects:
             submob.scale_in_place(1./factor)

mobject/tex_mobject.py

@@ -1,4 +1,4 @@
-from vectorized_mobject import VMobject
+from vectorized_mobject import VMobject, VGroup
 from svg_mobject import SVGMobject, VMobjectFromSVGPathstring
 from topics.geometry import BackgroundRectangle
 from helpers import *
@@ -74,8 +74,24 @@ class TexMobject(SVGMobject):
             result = result.replace("\n", " \\\\ \n ")
         result = " ".join([self.alignment, result])
         result = result.strip()
+        result = self.remove_stray_braces(result)
         return result
 
+    def remove_stray_braces(self, tex):
+        """
+        Makes TexMobject resiliant to unmatched { at start
+        """
+        num_lefts, num_rights = [
+            tex.count(char)
+            for char in "{}"
+        ]
+        if tex.startswith("{") and num_lefts > num_rights:
+            return tex[1:]
+        elif tex.endswith("}") and num_rights > num_lefts:
+            return tex[:-1]
+        return tex
+
+
     def get_tex_string(self):
         return self.tex_string
 
@@ -86,7 +102,7 @@ class TexMobject(SVGMobject):
         for expr in self.args:
             model = TexMobject(expr, **self.CONFIG)
             new_index = curr_index + len(model.submobjects)
-            new_submobjects.append(VMobject(
+            new_submobjects.append(VGroup(
                 *self.submobjects[curr_index:new_index]
             ))
             curr_index = new_index
@@ -129,8 +145,9 @@ class TextMobject(TexMobject):
 class Brace(TexMobject):
     CONFIG = {
         "buff" : 0.2,
-        "n_quads" : 3,
+        "width_multiplier" : 2,
-        "tex_string" : "\\underbrace{%s}"%(3*"\\qquad"),
+        "max_num_quads" : 15,
+        "min_num_quads" : 0,
     }
     def __init__(self, mobject, direction = DOWN, **kwargs):
         digest_config(self, kwargs, locals())
@@ -141,7 +158,11 @@ class Brace(TexMobject):
         target_width = right[0]-left[0]
 
         ## Adding int(target_width) qquads gives approximately the right width
-        tex_string = "\\underbrace{%s}"%(int(target_width)*"\\qquad")
+        num_quads = np.clip(
+            int(self.width_multiplier*target_width),
+            self.min_num_quads, self.max_num_quads
+        )
+        tex_string = "\\underbrace{%s}"%(num_quads*"\\qquad")
         TexMobject.__init__(self, tex_string, **kwargs)
         self.stretch_to_fit_width(target_width)
         self.shift(left - self.get_corner(UP+LEFT) + self.buff*DOWN)

scene/zoomed_scene.py

@@ -1,6 +1,7 @@
 import numpy as np
 
 from scene import Scene
+from animation.transform import FadeIn
 from mobject import Mobject
 from topics.geometry import Rectangle
 from camera import MovingCamera, Camera
@@ -18,6 +19,7 @@ class ZoomedScene(Scene):
         "zoomed_canvas_corner"      : UP+RIGHT,
         "zoomed_canvas_corner_buff" : DEFAULT_MOBJECT_TO_EDGE_BUFFER,
         "zoomed_camera_background"  : None,
+        "little_rectangle_start_position" : ORIGIN,
         "zoom_factor"               : 6,
         "square_color"              : WHITE,
         "zoom_activated"            : False,
@@ -28,6 +30,12 @@ class ZoomedScene(Scene):
         self.setup_zoomed_camera()
         self.zoom_activated = True
 
+    def animate_activate_zooming(self):
+        self.activate_zooming()
+        self.play(*map(FadeIn, [
+            self.little_rectangle, self.big_rectangle
+        ]))
+
     def disactivate_zooming(self):
         self.remove(self.big_rectangle, self.little_rectangle)
         self.zoom_activated = False
@@ -71,7 +79,9 @@ class ZoomedScene(Scene):
     def setup_zoomed_camera(self):
         self.little_rectangle = self.big_rectangle.copy()
         self.little_rectangle.scale(1./self.zoom_factor)
-        self.little_rectangle.center()
+        self.little_rectangle.move_to(
+            self.little_rectangle_start_position
+        )
         self.zoomed_camera = MovingCamera(
             self.little_rectangle,
             pixel_shape = self.zoomed_canvas_pixel_shape,

topics/characters.py

@@ -242,8 +242,8 @@ class PiCreatureBubbleIntroduction(AnimationGroup):
     }
     def __init__(self, pi_creature, *content, **kwargs):
         digest_config(self, kwargs)
-        if isinstance(content, Mobject):
+        if isinstance(content[0], Mobject):
-            bubble_content = content
+            bubble_content = content[0]
         else:
             bubble_content = TextMobject(*content)
         bubble = pi_creature.get_bubble(
@@ -390,11 +390,13 @@ class PiCreatureScene(Scene):
         first mobject being animated with each .play call
         """
         animations = Scene.compile_play_args_to_animation_list(self, *args)
-        if len(animations) == 0:
+        non_pi_creature_anims = filter(
-            return animations
+            lambda anim : anim.mobject not in self.get_pi_creatures(),
-        first_anim = animations[0]
+            animations
-        if isinstance(first_anim, Blink):
+        )
+        if len(non_pi_creature_anims) == 0:
             return animations
+        first_anim = non_pi_creature_anims[0]
         #Look at ending state
         first_anim.update(1)
         point_of_interest = first_anim.mobject.get_center()
@@ -405,10 +407,10 @@ class PiCreatureScene(Scene):
                 continue
             if pi_creature in first_anim.mobject.submobject_family():
                 continue
-            anims_with_pi_creature = [
+            anims_with_pi_creature = filter(
-                anim for anim in animations
+                lambda anim : pi_creature in anim.mobject.submobject_family(),
-                if pi_creature in anim.mobject.submobject_family()
+                animations
-            ]
+            )
             if anims_with_pi_creature:
                 for anim in anims_with_pi_creature:
                     if isinstance(anim, Transform):

topics/geometry.py

@@ -154,6 +154,7 @@ class DashedLine(Line):
         for p1, p2, include in zip(points, points[1:], includes):
             if include:
                 self.add(Line(p1, p2, **self.init_kwargs))
+        self.put_start_and_end_on(self.start, self.end)
         return self
 
     def get_start(self):

topics/number_line.py

@@ -16,6 +16,7 @@ class NumberLine(VMobject):
         "tick_frequency" : 1,
         "leftmost_tick" : None, #Defaults to ceil(x_min)
         "numbers_with_elongated_ticks" : [0],
+        "numbers_to_show" : None,
         "longer_tick_multiple" : 2,
         "number_at_center" : 0,
         "propogate_style_to_family" : True
@@ -62,11 +63,19 @@ class NumberLine(VMobject):
         )
 
     def point_to_number(self, point):
-        dist_from_left = float(point[0]-self.main_line.get_left()[0])
+        left_point, right_point = self.main_line.get_start_and_end()
-        num_dist_from_left = dist_from_left/self.space_unit_to_num
+        full_vect = right_point-left_point
-        return self.x_min + num_dist_from_left
+        def distance_from_left(p):
+            return np.dot(p-left_point, full_vect)/np.linalg.norm(full_vect)
+
+        return interpolate(
+            self.x_min, self.x_max, 
+            distance_from_left(point)/distance_from_left(right_point)
+        )
 
     def default_numbers_to_display(self):
+        if self.numbers_to_show is not None:
+            return self.numbers_to_show
         return np.arange(self.leftmost_tick, self.x_max, 1)
 
     def get_vertical_number_offset(self, direction = DOWN):

topics/three_dimensions.py

@@ -1,6 +1,8 @@
 
 from helpers import *
 
+from mobject.vectorized_mobject import VGroup
+from topics.geometry import Square
 from scene import Scene
 from camera import Camera
 
@@ -60,7 +62,24 @@ class ThreeDScene(Scene):
         "camera_class" : ThreeDCamera,
     }
 
-
+##############
+
+class Cube(VGroup):
+    CONFIG = {
+        "fill_opacity" : 0.75,
+        "fill_color" : BLUE,
+        "stroke_width" : 0,
+        "propogate_style_to_family" : True,
+        "side_length" : 2,
+    }
+    def generate_points(self):
+        faces = [
+            Square(side_length = self.side_length).shift(OUT).apply_function(
+                lambda p : np.dot(p, z_to_vector(vect).T)
+            )
+            for vect in IN, OUT, LEFT, RIGHT, UP, DOWN
+        ]
+        self.add(*faces)