Merge pull request #375 from 3b1b/shadows

Shadows

active_projects/shadows.py

@@ -57,6 +57,10 @@ class ShowShadows(ThreeDScene):
         "camera_config": {
             "light_source_start_point": 10 * OUT,
             "frame_center": [0, 0, 0.5],
+        },
+        "initial_orientation_config": {
+            "phi": 60 * DEGREES,
+            "theta": -120 * DEGREES,
         }
     }
 
@@ -144,8 +148,7 @@ class ShowShadows(ThreeDScene):
         temp_shadow = updating_mobject_from_func(lambda: get_shadow(obj3d))
         self.add(temp_shadow)
         self.move_camera(
-            phi=60 * DEGREES,
-            theta=-120 * DEGREES,
+            **self.initial_orientation_config,
             added_anims=[
                 LaggedStart(DrawBorderThenFill, obj3d)
             ],

camera/camera.py

@@ -300,7 +300,7 @@ class Camera(object):
         ctx.set_matrix(cairo.Matrix(
             fdiv(pw, fw), 0,
             0, -fdiv(ph, fh),
-            (pw / 2) + fc[0] * fdiv(pw, fw),
+            (pw / 2) - fc[0] * fdiv(pw, fw),
             (ph / 2) + fc[1] * fdiv(ph, fh),
         ))
         self.cache_cairo_context(pixel_array, ctx)

for_3b1b_videos/common_scenes.py

@@ -11,6 +11,7 @@ from animation.creation import DrawBorderThenFill
 from animation.creation import Write
 from animation.creation import FadeIn
 from animation.creation import FadeOut
+from continual_animation.continual_animation import ContinualMovement
 from mobject.svg.tex_mobject import TextMobject
 from mobject.types.vectorized_mobject import VGroup
 from scene.scene import Scene
@@ -18,12 +19,15 @@ from scene.moving_camera_scene import MovingCameraScene
 from for_3b1b_videos.pi_creature_animations import Blink
 from for_3b1b_videos.pi_creature import Mortimer
 from for_3b1b_videos.pi_creature import Randolph
+from for_3b1b_videos.pi_creature_scene import PiCreatureScene
 from mobject.geometry import Line
 from mobject.geometry import DashedLine
 from mobject.geometry import Rectangle
 from mobject.geometry import Square
 from mobject.svg.drawings import PatreonLogo
 from mobject.svg.drawings import Logo
+from utils.space_ops import get_norm
+from utils.space_ops import normalize
 
 
 class OpeningQuote(Scene):
@@ -147,7 +151,7 @@ class PatreonThanks(Scene):
             last_group = group
 
 
-class PatreonEndScreen(PatreonThanks):
+class PatreonEndScreen(PatreonThanks, PiCreatureScene):
     CONFIG = {
         "n_patron_columns": 3,
         "max_patron_width": 3.5,
@@ -155,6 +159,7 @@ class PatreonEndScreen(PatreonThanks):
         "randomize_order": True,
         "capitalize": True,
         "name_y_spacing": 0.7,
+        "thanks_words": "Funded by the community, with special thanks to:",
     }
 
     def construct(self):
@@ -169,10 +174,10 @@ class PatreonEndScreen(PatreonThanks):
                 for patron in self.specific_patrons
             ]
 
-        self.add_title()
+        # self.add_title()
         self.scroll_through_patrons()
 
-    def add_title(self):
+    def create_pi_creatures(self):
         title = self.title = TextMobject("Clicky Stuffs")
         title.scale(1.5)
         title.to_edge(UP, buff=MED_SMALL_BUFF)
@@ -184,6 +189,7 @@ class PatreonEndScreen(PatreonThanks):
             pi.look(DOWN)
             pi.next_to(title, vect, buff=MED_LARGE_BUFF)
         self.add_foreground_mobjects(title, randy, morty)
+        return self.pi_creatures
 
     def scroll_through_patrons(self):
         logo_box = Square(side_length=2.5)
@@ -202,12 +208,13 @@ class PatreonEndScreen(PatreonThanks):
         line = DashedLine(FRAME_X_RADIUS * LEFT, FRAME_X_RADIUS * RIGHT)
         line.move_to(ORIGIN)
 
-        thanks = TextMobject("Funded by the community, with special thanks to:")
+        thanks = TextMobject(self.thanks_words)
         thanks.scale(0.9)
         thanks.next_to(black_rect.get_bottom(), UP, SMALL_BUFF)
         thanks.set_color(YELLOW)
         underline = Line(LEFT, RIGHT)
-        underline.set_width(thanks.get_width() + MED_SMALL_BUFF)
+        underline.match_width(thanks)
+        underline.scale(1.1)
         underline.next_to(thanks, DOWN, SMALL_BUFF)
         thanks.add(underline)
 
@@ -233,13 +240,22 @@ class PatreonEndScreen(PatreonThanks):
         thanks.to_edge(RIGHT)
         columns.next_to(thanks, DOWN, 3 * LARGE_BUFF)
 
-        self.add(columns, black_rect, line, thanks)
-        self.play(
-            columns.move_to, 2 * DOWN, DOWN,
-            columns.align_to, thanks, {"alignment_vect": RIGHT},
-            rate_func=None,
-            run_time=self.run_time,
+        columns.generate_target()
+        columns.target.move_to(2 * DOWN, DOWN)
+        columns.target.align_to(
+            thanks, alignment_vect=RIGHT
         )
+        vect = columns.target.get_center() - columns.get_center()
+        distance = get_norm(vect)
+        wait_time = 20
+        columns_shift = ContinualMovement(
+            columns,
+            direction=normalize(vect),
+            rate=(distance / wait_time)
+        )
+
+        self.add(columns_shift, black_rect, line, thanks)
+        self.wait(wait_time)
 
 
 class LogoGenerationTemplate(MovingCameraScene):

mobject/geometry.py

@@ -481,6 +481,19 @@ class DashedLine(Line):
             return self.end
 
 
+class Elbow(VMobject):
+    CONFIG = {
+        "width": 0.2,
+        "angle": 0,
+    }
+
+    def __init__(self, **kwargs):
+        VMobject.__init__(self, **kwargs)
+        self.set_points_as_corners([UP, UP + RIGHT, RIGHT])
+        self.set_width(self.width, about_point=ORIGIN)
+        self.rotate(self.angle, about_point=ORIGIN)
+
+
 class Arrow(Line):
     CONFIG = {
         "tip_length": 0.25,

mobject/mobject.py

@@ -18,7 +18,6 @@ from utils.iterables import list_update
 from utils.iterables import remove_list_redundancies
 from utils.paths import straight_path
 from utils.space_ops import angle_of_vector
-from utils.space_ops import complex_to_R3
 from utils.space_ops import rotation_matrix
 from utils.simple_functions import get_num_args
 from utils.space_ops import get_norm
@@ -270,10 +269,15 @@ class Mobject(Container):
         return self
 
     def apply_complex_function(self, function, **kwargs):
-        return self.apply_function(
-            lambda x_y_z: complex_to_R3(function(complex(x_y_z[0], x_y_z[1]))),
-            **kwargs
-        )
+        def R3_func(point):
+            x, y, z = point
+            xy_complex = function(complex(x, y))
+            return [
+                xy_complex.real,
+                xy_complex.imag,
+                z
+            ]
+        return self.apply_function(R3_func)
 
     def wag(self, direction=RIGHT, axis=DOWN, wag_factor=1.0):
         for mob in self.family_members_with_points():

mobject/three_dimensions.py

@@ -42,7 +42,7 @@ class ParametricSurface(VGroup):
         if self.should_make_jagged:
             self.make_jagged()
 
-    def setup_in_uv_space(self):
+    def get_u_values_and_v_values(self):
         res = tuplify(self.resolution)
         if len(res) == 1:
             u_res = v_res = res[0]
@@ -55,9 +55,14 @@ class ParametricSurface(VGroup):
 
         u_values = np.linspace(u_min, u_max, u_res + 1)
         v_values = np.linspace(v_min, v_max, v_res + 1)
+
+        return u_values, v_values
+
+    def setup_in_uv_space(self):
+        u_values, v_values = self.get_u_values_and_v_values()
         faces = VGroup()
-        for i in range(u_res):
-            for j in range(v_res):
+        for i in range(len(u_values) - 1):
+            for j in range(len(v_values) - 1):
                 u1, u2 = u_values[i:i + 2]
                 v1, v2 = v_values[j:j + 2]
                 face = ThreeDVMobject()

mobject/value_tracker.py

@@ -41,3 +41,13 @@ class ExponentialValueTracker(ValueTracker):
 
     def set_value(self, value):
         return ValueTracker.set_value(self, np.log(value))
+
+
+class ComplexValueTracker(ValueTracker):
+    def get_value(self):
+        return complex(*self.points[0, :2])
+
+    def set_value(self, z):
+        z = complex(z)
+        self.points[0, :2] = (z.real, z.imag)
+        return self

old_projects/for_flammy.py

@@ -0,0 +1,339 @@
+from big_ol_pile_of_manim_imports import *
+from old_projects.sphere_area import *
+
+
+class MadAtMathologer(PiCreatureScene):
+    def create_pi_creature(self):
+        return Mortimer().to_corner(DR)
+
+    def construct(self):
+        morty = self.pi_creature
+        self.play(morty.change, "angry")
+        self.wait(3)
+        self.play(morty.change, "heistant")
+        self.wait(2)
+        self.play(morty.change, "shruggie")
+        self.wait(3)
+
+
+class JustTheIntegral(Scene):
+    def construct(self):
+        tex = TexMobject("\\int_0^{\\pi / 2} \\cos(\\theta)d\\theta")
+        tex.scale(2)
+        self.add(tex)
+
+
+class SphereVideoWrapper(Scene):
+    def construct(self):
+        title = TextMobject("Surface area of a sphere")
+        title.scale(1.5)
+        title.to_edge(UP)
+        rect = ScreenRectangle(height=6)
+        rect.next_to(title, DOWN)
+        self.add(title)
+        self.play(ShowCreation(rect))
+        self.wait()
+
+
+class SphereRings(SecondProof):
+    CONFIG = {
+        "sphere_config": {
+            "resolution": (60, 60),
+        },
+    }
+
+    def construct(self):
+        self.setup_shapes()
+        self.grow_rings()
+        self.show_one_ring()
+        self.show_radial_line()
+        self.show_thickness()
+        self.flash_through_rings()
+
+    def grow_rings(self):
+        sphere = self.sphere
+        rings = self.rings
+        north_rings = rings[:len(rings) // 2]
+        sphere.set_fill(opacity=0)
+        sphere.set_stroke(WHITE, 0.5, opacity=0.5)
+        southern_mesh = VGroup(*[
+            face.copy() for face in sphere
+            if face.get_center()[2] < 0
+        ])
+        southern_mesh.set_stroke(WHITE, 0.1, 0.5)
+
+        self.play(Write(sphere))
+        self.wait()
+        self.play(
+            FadeOut(sphere),
+            FadeIn(southern_mesh),
+            FadeIn(north_rings),
+        )
+        self.wait(4)
+
+        self.north_rings = north_rings
+        self.southern_mesh = southern_mesh
+
+    def show_one_ring(self):
+        north_rings = self.north_rings
+        index = len(north_rings) // 2
+        ring = north_rings[index]
+        to_fade = VGroup(*[
+            nr for nr in north_rings
+            if nr is not ring
+        ])
+
+        north_rings.save_state()
+
+        circle = Circle()
+        circle.set_stroke(PINK, 5)
+        circle.set_width(ring.get_width())
+        circle.move_to(ring, IN)
+
+        thickness = ring.get_depth() * np.sqrt(2)
+        brace = Brace(Line(ORIGIN, 0.2 * RIGHT), UP)
+        brace.set_width(thickness)
+        brace.rotate(90 * DEGREES, RIGHT)
+        brace.rotate(45 * DEGREES, UP)
+        brace.move_to(1.5 * (RIGHT + OUT))
+        brace.set_stroke(WHITE, 1)
+        word = TextMobject("Thickness")
+        word.rotate(90 * DEGREES, RIGHT)
+        word.next_to(brace, RIGHT + OUT, buff=0)
+
+        self.play(
+            to_fade.set_fill, {"opacity": 0.2},
+            to_fade.set_stroke, {"opacity": 0.0},
+        )
+        self.move_camera(
+            phi=0, theta=-90 * DEGREES,
+            run_time=2,
+        )
+        self.stop_ambient_camera_rotation()
+        self.play(ShowCreation(circle))
+        self.play(FadeOut(circle))
+        self.move_camera(
+            phi=70 * DEGREES,
+            theta=-100 * DEGREES,
+            run_time=2,
+        )
+        self.begin_ambient_camera_rotation(0.02)
+        self.play(
+            GrowFromCenter(brace),
+            Write(word),
+        )
+        self.wait(2)
+        self.play(FadeOut(VGroup(brace, word)))
+
+        self.circum_circle = circle
+        self.thickness_label = VGroup(brace, word)
+        self.ring = ring
+
+    def show_radial_line(self):
+        ring = self.ring
+
+        point = ring.get_corner(RIGHT + IN)
+        R_line = Line(ORIGIN, point)
+        xy_line = Line(ORIGIN, self.sphere.get_right())
+        theta = np.arccos(np.dot(
+            normalize(R_line.get_vector()),
+            normalize(xy_line.get_vector())
+        ))
+        arc = Arc(angle=theta, radius=0.5)
+        arc.rotate(90 * DEGREES, RIGHT, about_point=ORIGIN)
+
+        theta = TexMobject("\\theta")
+        theta.rotate(90 * DEGREES, RIGHT)
+        theta.next_to(arc, RIGHT)
+        theta.shift(SMALL_BUFF * (LEFT + OUT))
+
+        R_label = TexMobject("R")
+        R_label.rotate(90 * DEGREES, RIGHT)
+        R_label.next_to(
+            R_line.get_center(), OUT + LEFT,
+            buff=SMALL_BUFF
+        )
+        VGroup(R_label, R_line).set_color(YELLOW)
+
+        z_axis_point = np.array(point)
+        z_axis_point[:2] = 0
+        r_line = DashedLine(z_axis_point, point)
+        r_line.set_color(RED)
+        r_label = TexMobject("R\\cos(\\theta)")
+        r_label.rotate(90 * DEGREES, RIGHT)
+        r_label.scale(0.7)
+        r_label.match_color(r_line)
+        r_label.set_stroke(width=0, background=True)
+        r_label.next_to(r_line, OUT, 0.5 * SMALL_BUFF)
+
+        VGroup(
+            R_label, xy_line, arc, R_label,
+            r_line, r_label,
+        ).set_shade_in_3d(True)
+
+        # self.stop_ambient_camera_rotation()
+        self.move_camera(
+            phi=85 * DEGREES,
+            theta=-100 * DEGREES,
+            added_anims=[
+                ring.set_fill, {"opacity": 0.5},
+                ring.set_stroke, {"opacity": 0.1},
+                ShowCreation(R_line),
+                FadeInFrom(R_label, IN),
+            ]
+        )
+        self.wait()
+        self.play(
+            FadeIn(xy_line),
+            ShowCreation(arc),
+            Write(theta),
+        )
+        self.wait()
+        self.play(
+            ShowCreation(r_line),
+            FadeInFrom(r_label, IN),
+        )
+        self.wait()
+        self.move_camera(
+            phi=70 * DEGREES,
+            theta=-110 * DEGREES,
+            run_time=3
+        )
+        self.wait(2)
+
+    def show_thickness(self):
+        brace, word = self.thickness_label
+        R_dtheta = TexMobject("R \\, d\\theta")
+        R_dtheta.rotate(90 * DEGREES, RIGHT)
+        R_dtheta.move_to(word, LEFT)
+
+        self.play(
+            GrowFromCenter(brace),
+            Write(R_dtheta)
+        )
+        self.wait(3)
+
+    def flash_through_rings(self):
+        rings = self.north_rings.copy()
+        rings.fade(1)
+        rings.sort_submobjects(lambda p: p[2])
+
+        for x in range(8):
+            self.play(LaggedStart(
+                ApplyMethod, rings,
+                lambda m: (m.set_fill, PINK, 0.5),
+                rate_func=there_and_back,
+                lag_ratio=0.1,
+                run_time=2,
+            ))
+
+
+class IntegralSymbols(Scene):
+    def construct(self):
+        int_sign = TexMobject("\\displaystyle \\int")
+        int_sign.set_height(1.5)
+        int_sign.move_to(5 * LEFT)
+
+        circumference, times, thickness = ctt = TextMobject(
+            "circumference", "$\\times$", "thickness"
+        )
+        circumference.set_color(MAROON_B)
+        ctt.next_to(int_sign, RIGHT, SMALL_BUFF)
+        area_brace = Brace(ctt, DOWN)
+        area_text = area_brace.get_text("Area of a ring")
+
+        all_rings = TextMobject("All rings")
+        all_rings.scale(0.5)
+        all_rings.next_to(int_sign, DOWN, SMALL_BUFF)
+        all_rings.shift(SMALL_BUFF * LEFT)
+
+        circum_formula = TexMobject(
+            "2\\pi", "R\\cos(\\theta)",
+        )
+        circum_formula[1].set_color(RED)
+        circum_formula.move_to(circumference)
+        circum_brace = Brace(circum_formula, UP)
+
+        R_dtheta = TexMobject("R \\, d\\theta")
+        R_dtheta.move_to(thickness, LEFT)
+        R_dtheta_brace = Brace(R_dtheta, UP)
+
+        zero, pi_halves = bounds = TexMobject("0", "\\pi / 2")
+        bounds.scale(0.5)
+        zero.move_to(all_rings)
+        pi_halves.next_to(int_sign, UP, SMALL_BUFF)
+        pi_halves.shift(SMALL_BUFF * RIGHT)
+
+        self.add(int_sign)
+        self.play(
+            GrowFromCenter(area_brace),
+            FadeInFrom(area_text, UP),
+        )
+        self.wait()
+        self.play(FadeInFromDown(circumference))
+        self.play(
+            FadeInFromDown(thickness),
+            Write(times)
+        )
+        self.play(Write(all_rings))
+        self.wait()
+
+        self.play(
+            circumference.next_to, circum_brace, UP, MED_SMALL_BUFF,
+            circumference.shift, SMALL_BUFF * UR,
+            GrowFromCenter(circum_brace),
+        )
+        self.play(FadeInFrom(circum_formula, UP))
+        self.wait()
+        self.play(
+            thickness.next_to, circumference, RIGHT, MED_SMALL_BUFF,
+            GrowFromCenter(R_dtheta_brace),
+            area_brace.stretch, 0.84, 0, {"about_edge": LEFT},
+            MaintainPositionRelativeTo(area_text, area_brace),
+        )
+        self.play(FadeInFrom(R_dtheta, UP))
+        self.wait()
+        self.play(ReplacementTransform(all_rings, bounds))
+        self.wait()
+
+        # RHS
+        rhs = TexMobject(
+            "\\displaystyle =", "2\\pi R^2", "\\int_0^{\\pi / 2}",
+            "\\cos(\\theta)", "d\\theta",
+        )
+        rhs.set_color_by_tex("cos", RED)
+        rhs.next_to(R_dtheta, RIGHT)
+        int_brace = Brace(rhs[2:], DOWN)
+        q_marks = int_brace.get_text("???")
+        one = TexMobject("1")
+        one.move_to(q_marks)
+
+        self.play(FadeInFrom(rhs, 4 * LEFT))
+        self.wait()
+        self.play(CircleThenFadeAround(rhs[1]))
+        self.wait()
+        self.play(CircleThenFadeAround(rhs[2:]))
+        self.wait()
+        self.play(
+            GrowFromCenter(int_brace),
+            LaggedStart(
+                FadeInFrom, q_marks,
+                lambda m: (m, UP),
+            )
+        )
+        self.wait()
+        self.play(ReplacementTransform(q_marks, one))
+        self.wait()
+
+
+class ShamelessPlug(TeacherStudentsScene):
+    def construct(self):
+        self.student_says(
+            "But why $4\\pi R^2$?",
+            target_mode="maybe"
+        )
+        self.change_student_modes(
+            "erm", "maybe", "happy",
+            added_anims=[self.teacher.change, "happy"]
+        )
+        self.wait(3)

old_projects/quaternions.py

@@ -1,47 +1,4 @@
 from big_ol_pile_of_manim_imports import *
-# from pprint import pprint
-
-
-# Helpers
-def get_three_d_scene_config(high_quality=True):
-    hq_config = {
-        "camera_config": {
-            "should_apply_shading": True,
-            "exponential_projection": True,
-        },
-        "three_d_axes_config": {
-            "num_axis_pieces": 1,
-            "number_line_config": {
-                "unit_size": 2,
-                # "tick_frequency": 0.5,
-                "tick_frequency": 1,
-                "numbers_with_elongated_ticks": [0, 1, 2],
-                "stroke_width": 2,
-            }
-        },
-        "sphere_config": {
-            "radius": 2,
-            "resolution": (24, 48),
-        }
-    }
-    lq_added_config = {
-        "camera_config": {
-            "should_apply_shading": False,
-        },
-        "three_d_axes_config": {
-            "num_axis_pieces": 1,
-        },
-        "sphere_config": {
-            "resolution": (12, 24),
-        }
-    }
-    if high_quality:
-        return hq_config
-    else:
-        return merge_config([
-            lq_added_config,
-            hq_config
-        ])
 
 
 def q_mult(q1, q2):
@@ -459,53 +416,6 @@ class RubiksCube(VGroup):
 
 
 # Abstract scenes
-class SpecialThreeDScene(ThreeDScene):
-    CONFIG = {
-        "cut_axes_at_radius": True,
-    }
-
-    def __init__(self, **kwargs):
-        digest_config(self, kwargs)
-        if self.frame_duration == PRODUCTION_QUALITY_FRAME_DURATION:
-            high_quality = True
-        else:
-            high_quality = False
-        default_config = get_three_d_scene_config(high_quality)
-        config = merge_config([self.CONFIG, kwargs, default_config])
-        ThreeDScene.__init__(self, **config)
-
-    def get_axes(self):
-        axes = ThreeDAxes(**self.three_d_axes_config)
-        for axis in axes:
-            if self.cut_axes_at_radius:
-                p0 = axis.main_line.get_start()
-                p1 = axis.number_to_point(-1)
-                p2 = axis.number_to_point(1)
-                p3 = axis.main_line.get_end()
-                new_pieces = VGroup(
-                    Line(p0, p1), Line(p1, p2), Line(p2, p3),
-                )
-                for piece in new_pieces:
-                    piece.shade_in_3d = True
-                new_pieces.match_style(axis.pieces)
-                axis.pieces.submobjects = new_pieces.submobjects
-            for tick in axis.tick_marks:
-                tick.add(VectorizedPoint(
-                    1.5 * tick.get_center(),
-                ))
-        return axes
-
-    def get_sphere(self):
-        return Sphere(**self.sphere_config)
-
-    def get_default_camera_position(self):
-        return {
-            "phi": 70 * DEGREES,
-            "theta": -110 * DEGREES,
-        }
-
-
-# Animated scenes
 
 
 class ManyNumberSystems(Scene):

old_projects/zeta.py

@@ -3265,18 +3265,23 @@ class Thumbnail(ZetaTransformationScene):
         "anchor_density" : 35
     }
     def construct(self):
+        self.y_min = -4
+        self.y_max = 4
+        self.x_min = 1
+        self.x_max = int(FRAME_X_RADIUS+2)
         self.add_transformable_plane()
         self.add_extra_plane_lines_for_zeta()
         self.add_reflected_plane()
-        self.apply_zeta_function()
+        # self.apply_zeta_function()
         self.plane.set_stroke(width = 4)
 
         div_sum = TexMobject("-\\frac{1}{12} = ", "1+2+3+4+\\cdots")
         div_sum.set_width(FRAME_WIDTH-1)
         div_sum.to_edge(DOWN)
         div_sum.set_color(YELLOW)
-        for mob in div_sum.submobjects:
-            mob.add_to_back(BackgroundRectangle(mob))
+        div_sum.set_background_stroke(width=8)
+        # for mob in div_sum.submobjects:
+        #     mob.add_to_back(BackgroundRectangle(mob))
 
         zeta = TexMobject("\\zeta(s)")
         zeta.set_height(FRAME_Y_RADIUS-1)
@@ -3286,7 +3291,7 @@ class Thumbnail(ZetaTransformationScene):
         million.set_width(FRAME_X_RADIUS+1)
         million.to_edge(UP+RIGHT)
         million.set_color(GREEN_B)
-        million.add_background_rectangle()
+        million.set_background_stroke(width=8)
 
         self.add(div_sum, million, zeta)
 

scene/three_d_scene.py

@@ -1,15 +1,26 @@
-from constants import *
-
+from constants import DEGREES
+from constants import PRODUCTION_QUALITY_FRAME_DURATION
 from continual_animation.update import ContinualGrowValue
 from animation.transform import ApplyMethod
 from camera.three_d_camera import ThreeDCamera
+from mobject.coordinate_systems import ThreeDAxes
+from mobject.geometry import Line
+from mobject.three_dimensions import Sphere
+from mobject.types.vectorized_mobject import VGroup
+from mobject.types.vectorized_mobject import VectorizedPoint
 from scene.scene import Scene
+from utils.config_ops import digest_config
+from utils.config_ops import merge_config
 
 
 class ThreeDScene(Scene):
     CONFIG = {
         "camera_class": ThreeDCamera,
         "ambient_camera_rotation": None,
+        "default_angled_camera_orientation_kwargs": {
+            "phi": 70 * DEGREES,
+            "theta": -135 * DEGREES,
+        }
     }
 
     def set_camera_orientation(self, phi=None, theta=None, distance=None, gamma=None):
@@ -22,7 +33,7 @@ class ThreeDScene(Scene):
         if gamma is not None:
             self.camera.set_gamma(gamma)
 
-    def begin_ambient_camera_rotation(self, rate=0.05):
+    def begin_ambient_camera_rotation(self, rate=0.02):
         self.ambient_camera_rotation = ContinualGrowValue(
             self.camera.theta_tracker,
             rate=rate
@@ -86,3 +97,90 @@ class ThreeDScene(Scene):
 
     def remove_fixed_in_frame_mobjects(self, *mobjects):
         self.camera.remove_fixed_in_frame_mobjects(*mobjects)
+
+    ##
+    def set_to_default_angled_camera_orientation(self, **kwargs):
+        config = dict(self.default_camera_orientation_kwargs)
+        config.update(kwargs)
+        self.set_camera_orientation(**config)
+
+
+class SpecialThreeDScene(ThreeDScene):
+    CONFIG = {
+        "cut_axes_at_radius": True,
+        "camera_config": {
+            "should_apply_shading": True,
+            "exponential_projection": True,
+        },
+        "three_d_axes_config": {
+            "num_axis_pieces": 1,
+            "number_line_config": {
+                "unit_size": 2,
+                "tick_frequency": 1,
+                "numbers_with_elongated_ticks": [0, 1, 2],
+                "stroke_width": 2,
+            }
+        },
+        "sphere_config": {
+            "radius": 2,
+            "resolution": (24, 48),
+        },
+        "default_angled_camera_position": {
+            "phi": 70 * DEGREES,
+            "theta": -110 * DEGREES,
+        },
+        # When scene is extracted with -l flag, this
+        # configuration will override the above configuration.
+        "low_quality_config": {
+            "camera_config": {
+                "should_apply_shading": False,
+            },
+            "three_d_axes_config": {
+                "num_axis_pieces": 1,
+            },
+            "sphere_config": {
+                "resolution": (12, 24),
+            }
+        }
+    }
+
+    def __init__(self, **kwargs):
+        digest_config(self, kwargs)
+        if self.frame_duration == PRODUCTION_QUALITY_FRAME_DURATION:
+            config = {}
+        else:
+            config = self.low_quality_config
+        ThreeDScene.__init__(self, **merge_config([kwargs, config]))
+
+    def get_axes(self):
+        axes = ThreeDAxes(**self.three_d_axes_config)
+        for axis in axes:
+            if self.cut_axes_at_radius:
+                p0 = axis.main_line.get_start()
+                p1 = axis.number_to_point(-1)
+                p2 = axis.number_to_point(1)
+                p3 = axis.main_line.get_end()
+                new_pieces = VGroup(
+                    Line(p0, p1), Line(p1, p2), Line(p2, p3),
+                )
+                for piece in new_pieces:
+                    piece.shade_in_3d = True
+                new_pieces.match_style(axis.pieces)
+                axis.pieces.submobjects = new_pieces.submobjects
+            for tick in axis.tick_marks:
+                tick.add(VectorizedPoint(
+                    1.5 * tick.get_center(),
+                ))
+        return axes
+
+    def get_sphere(self, **kwargs):
+        config = merge_config([kwargs, self.sphere_config])
+        return Sphere(**config)
+
+    def get_default_camera_position(self):
+        return self.default_angled_camera_position
+
+    def set_camera_to_default_position(self):
+        self.set_camera_orientation(
+            **self.default_angled_camera_position
+        )

utils/config_ops.py

@@ -57,6 +57,13 @@ def digest_config(obj, kwargs, caller_locals={}):
 
 
 def merge_config(all_dicts):
+    """
+    Creates a dict whose keyset is the union of all the
+    input dictionaries.  The value for each key is based
+    on the first dict in the list with that key.
+
+    When values are dictionaries, it is applied recursively
+    """
     all_config = reduce(op.add, [list(d.items()) for d in all_dicts])
     config = dict()
     for c in all_config: