Example Scenes¶
After understanding the previous knowledge, we can understand more scenes.
Many example scenes are given in example_scenes.py, let’s start with
the simplest and one by one.
InteractiveDevlopment¶
InteractiveDevelopment¶
from manimx import *
class InteractiveDevelopment(Scene):
def construct(self):
circle = Circle()
circle.set_fill(BLUE, opacity=0.5)
circle.set_stroke(BLUE_E, width=4)
square = Square()
self.play(ShowCreation(square))
self.wait()
# This opens an iPython terminal where you can keep writing
# lines as if they were part of this construct method.
# In particular, 'square', 'circle' and 'self' will all be
# part of the local namespace in that terminal.
self.embed()
# Try copying and pasting some of the lines below into
# the interactive shell
self.play(ReplacementTransform(square, circle))
self.wait()
self.play(circle.animate.stretch(4, 0))
self.play(Rotate(circle, 90 * DEGREES))
self.play(circle.animate.shift(2 * RIGHT).scale(0.25))
text = Text("""
In general, using the interactive shell
is very helpful when developing new scenes
""")
self.play(Write(text))
# In the interactive shell, you can just type
# play, add, remove, clear, wait, save_state and restore,
# instead of self.play, self.add, self.remove, etc.
# To interact with the window, type touch(). You can then
# scroll in the window, or zoom by holding down 'z' while scrolling,
# and change camera perspective by holding down 'd' while moving
# the mouse. Press 'r' to reset to the standard camera position.
# Press 'q' to stop interacting with the window and go back to
# typing new commands into the shell.
# In principle you can customize a scene to be responsive to
# mouse and keyboard interactions
always(circle.move_to, self.mouse_point)
This scene is similar to what we wrote in Quick Start. And how to interact has been written in the comments. No more explanation here.
AnimatingMethods¶
AnimatingMethods¶
class AnimatingMethods(Scene):
def construct(self):
grid = OldTex(r"\pi").get_grid(10, 10, height=4)
self.add(grid)
# You can animate the application of mobject methods with the
# ".animate" syntax:
self.play(grid.animate.shift(LEFT))
# Alternatively, you can use the older syntax by passing the
# method and then the arguments to the scene's "play" function:
self.play(grid.shift, LEFT)
# Both of those will interpolate between the mobject's initial
# state and whatever happens when you apply that method.
# For this example, calling grid.shift(LEFT) would shift the
# grid one unit to the left, but both of the previous calls to
# "self.play" animate that motion.
# The same applies for any method, including those setting colors.
self.play(grid.animate.set_color(YELLOW))
self.wait()
self.play(grid.animate.set_submobject_colors_by_gradient(BLUE, GREEN))
self.wait()
self.play(grid.animate.set_height(TAU - MED_SMALL_BUFF))
self.wait()
# The method Mobject.apply_complex_function lets you apply arbitrary
# complex functions, treating the points defining the mobject as
# complex numbers.
self.play(grid.animate.apply_complex_function(np.exp), run_time=5)
self.wait()
# Even more generally, you could apply Mobject.apply_function,
# which takes in functions form R^3 to R^3
self.play(
grid.animate.apply_function(
lambda p: [
p[0] + 0.5 * math.sin(p[1]),
p[1] + 0.5 * math.sin(p[0]),
p[2]
]
),
run_time=5,
)
self.wait()
The new usage in this scene is .get_grid() and self.play(mob.animate.method(args)).
.get_grid()method will return a new mobject containing multiple copies of this one arranged in a grid.self.play(mob.animate.method(args))animates the method, and the details are in the comments above.
TextExample¶
TextExample¶
class TextExample(Scene):
def construct(self):
# To run this scene properly, you should have "Consolas" font in your computer
# for full usage, you can see https://github.com/3b1b/manim/pull/680
text = Text("Here is a text", font="Consolas", font_size=90)
difference = Text(
"""
The most important difference between Text and TexText is that\n
you can change the font more easily, but can't use the LaTeX grammar
""",
font="Arial", font_size=24,
# t2c is a dict that you can choose color for different text
t2c={"Text": BLUE, "TexText": BLUE, "LaTeX": ORANGE}
)
VGroup(text, difference).arrange(DOWN, buff=1)
self.play(Write(text))
self.play(FadeIn(difference, UP))
self.wait(3)
fonts = Text(
"And you can also set the font according to different words",
font="Arial",
t2f={"font": "Consolas", "words": "Consolas"},
t2c={"font": BLUE, "words": GREEN}
)
fonts.set_width(FRAME_WIDTH - 1)
slant = Text(
"And the same as slant and weight",
font="Consolas",
t2s={"slant": ITALIC},
t2w={"weight": BOLD},
t2c={"slant": ORANGE, "weight": RED}
)
VGroup(fonts, slant).arrange(DOWN, buff=0.8)
self.play(FadeOut(text), FadeOut(difference, shift=DOWN))
self.play(Write(fonts))
self.wait()
self.play(Write(slant))
self.wait()
The new classes in this scene are Text, VGroup, Write, FadeIn and FadeOut.
Textcan create text, define fonts, etc. The usage ais clearly reflected in the above examples.VGroupcan put multipleVMobjecttogether as a whole. In the example, the.arrange()method is called to arrange the sub-mobjects in sequence downward (DOWN), and the spacing isbuff.Writeis an animation that shows similar writing effects.FadeInfades the object in, the second parameter indicates the direction of the fade in.FadeOutfades out the object, the second parameter indicates the direction of the fade out.
TexTransformExample¶
TexTransformExample¶
class TexTransformExample(Scene):
def construct(self):
to_isolate = ["B", "C", "=", "(", ")"]
lines = VGroup(
# Passing in muliple arguments to Tex will result
# in the same expression as if those arguments had
# been joined together, except that the submobject
# hierarchy of the resulting mobject ensure that the
# Tex mobject has a subject corresponding to
# each of these strings. For example, the Tex mobject
# below will have 5 subjects, corresponding to the
# expressions [A^2, +, B^2, =, C^2]
OldTex("A^2", "+", "B^2", "=", "C^2"),
# Likewise here
OldTex("A^2", "=", "C^2", "-", "B^2"),
# Alternatively, you can pass in the keyword argument
# "isolate" with a list of strings that should be out as
# their own submobject. So the line below is equivalent
# to the commented out line below it.
OldTex("A^2 = (C + B)(C - B)", isolate=["A^2", *to_isolate]),
# OldTex("A^2", "=", "(", "C", "+", "B", ")", "(", "C", "-", "B", ")"),
OldTex("A = \\sqrt{(C + B)(C - B)}", isolate=["A", *to_isolate])
)
lines.arrange(DOWN, buff=LARGE_BUFF)
for line in lines:
line.set_color_by_tex_to_color_map({
"A": BLUE,
"B": TEAL,
"C": GREEN,
})
play_kw = {"run_time": 2}
self.add(lines[0])
# The animation TransformMatchingTex will line up parts
# of the source and target which have matching tex strings.
# Here, giving it a little path_arc makes each part sort of
# rotate into their final positions, which feels appropriate
# for the idea of rearranging an equation
self.play(
TransformMatchingTex(
lines[0].copy(), lines[1],
path_arc=90 * DEGREES,
),
**play_kw
)
self.wait()
# Now, we could try this again on the next line...
self.play(
TransformMatchingTex(lines[1].copy(), lines[2]),
**play_kw
)
self.wait()
# ...and this looks nice enough, but since there's no tex
# in lines[2] which matches "C^2" or "B^2", those terms fade
# out to nothing while the C and B terms fade in from nothing.
# If, however, we want the C^2 to go to C, and B^2 to go to B,
# we can specify that with a key map.
self.play(FadeOut(lines[2]))
self.play(
TransformMatchingTex(
lines[1].copy(), lines[2],
key_map={
"C^2": "C",
"B^2": "B",
}
),
**play_kw
)
self.wait()
# And to finish off, a simple TransformMatchingShapes would work
# just fine. But perhaps we want that exponent on A^2 to transform into
# the square root symbol. At the moment, lines[2] treats the expression
# A^2 as a unit, so we might create a new version of the same line which
# separates out just the A. This way, when TransformMatchingTex lines up
# all matching parts, the only mismatch will be between the "^2" from
# new_line2 and the "\sqrt" from the final line. By passing in,
# transform_mismatches=True, it will transform this "^2" part into
# the "\sqrt" part.
new_line2 = OldTex("A^2 = (C + B)(C - B)", isolate=["A", *to_isolate])
new_line2.replace(lines[2])
new_line2.match_style(lines[2])
self.play(
TransformMatchingTex(
new_line2, lines[3],
transform_mismatches=True,
),
**play_kw
)
self.wait(3)
self.play(FadeOut(lines, RIGHT))
# Alternatively, if you don't want to think about breaking up
# the tex strings deliberately, you can TransformMatchingShapes,
# which will try to line up all pieces of a source mobject with
# those of a target, regardless of the submobject hierarchy in
# each one, according to whether those pieces have the same
# shape (as best it can).
source = Text("the morse code", height=1)
target = Text("here come dots", height=1)
self.play(Write(source))
self.wait()
kw = {"run_time": 3, "path_arc": PI / 2}
self.play(TransformMatchingShapes(source, target, **kw))
self.wait()
self.play(TransformMatchingShapes(target, source, **kw))
self.wait()
The new classes in this scene are Tex, TexText, TransformMatchingTex
and TransformMatchingShapes.
Texuses LaTeX to create mathematical formulas.TexTextuses LaTeX to create text.TransformMatchingTeXautomatically transforms sub-objects according to the similarities and differences of tex inTex.TransformMatchingShapesautomatically transform sub-objects directly based on the similarities and differences of the object point sets.
UpdatersExample¶
UpdatersExample¶
class UpdatersExample(Scene):
def construct(self):
square = Square()
square.set_fill(BLUE_E, 1)
# On all all frames, the constructor Brace(square, UP) will
# be called, and the mobject brace will set its data to match
# that of the newly constructed object
brace = always_redraw(Brace, square, UP)
text, number = label = VGroup(
Text("Width = "),
DecimalNumber(
0,
show_ellipsis=True,
num_decimal_places=2,
include_sign=True,
)
)
label.arrange(RIGHT)
# This ensures that the method deicmal.next_to(square)
# is called on every frame
always(label.next_to, brace, UP)
# You could also write the following equivalent line
# label.add_updater(lambda m: m.next_to(brace, UP))
# If the argument itself might change, you can use f_always,
# for which the arguments following the initial Mobject method
# should be functions returning arguments to that method.
# The following line ensures that decimal.set_value(square.get_y())
# is called every frame
f_always(number.set_value, square.get_width)
# You could also write the following equivalent line
# number.add_updater(lambda m: m.set_value(square.get_width()))
self.add(square, brace, label)
# Notice that the brace and label track with the square
self.play(
square.animate.scale(2),
rate_func=there_and_back,
run_time=2,
)
self.wait()
self.play(
square.animate.set_width(5, stretch=True),
run_time=3,
)
self.wait()
self.play(
square.animate.set_width(2),
run_time=3
)
self.wait()
# In general, you can alway call Mobject.add_updater, and pass in
# a function that you want to be called on every frame. The function
# should take in either one argument, the mobject, or two arguments,
# the mobject and the amount of time since the last frame.
now = self.time
w0 = square.get_width()
square.add_updater(
lambda m: m.set_width(w0 * math.cos(self.time - now))
)
self.wait(4 * PI)
The new classes and usage in this scene are always_redraw(), DecimalNumber, .to_edge(),
.center(), always(), f_always(), .set_y() and .add_updater().
always_redraw()function create a new mobject every frame.DecimalNumberis a variable number, speed it up by breaking it intoTextcharacters..to_edge()means to place the object on the edge of the screen..center()means to place the object in the center of the screen.always(f, x)means that a certain function (f(x)) is executed every frame.f_always(f, g)is similar toalways, executedf(g())every frame..set_y()means to set the ordinate of the object on the screen..add_updater()sets an update function for the object. For example:mob1.add_updater(lambda mob: mob.next_to(mob2))meansmob1.next_to(mob2)is executed every frame.
CoordinateSystemExample¶
CoordinateSystemExample¶
class CoordinateSystemExample(Scene):
def construct(self):
axes = Axes(
# x-axis ranges from -1 to 10, with a default step size of 1
x_range=(-1, 10),
# y-axis ranges from -2 to 2 with a step size of 0.5
y_range=(-2, 2, 0.5),
# The axes will be stretched so as to match the specified
# height and width
height=6,
width=10,
# Axes is made of two NumberLine mobjects. You can specify
# their configuration with axis_config
axis_config={
"stroke_color": GREY_A,
"stroke_width": 2,
},
# Alternatively, you can specify configuration for just one
# of them, like this.
y_axis_config={
"include_tip": False,
}
)
# Keyword arguments of add_coordinate_labels can be used to
# configure the DecimalNumber mobjects which it creates and
# adds to the axes
axes.add_coordinate_labels(
font_size=20,
num_decimal_places=1,
)
self.add(axes)
# Axes descends from the CoordinateSystem class, meaning
# you can call call axes.coords_to_point, abbreviated to
# axes.c2p, to associate a set of coordinates with a point,
# like so:
dot = Dot(color=RED)
dot.move_to(axes.c2p(0, 0))
self.play(FadeIn(dot, scale=0.5))
self.play(dot.animate.move_to(axes.c2p(3, 2)))
self.wait()
self.play(dot.animate.move_to(axes.c2p(5, 0.5)))
self.wait()
# Similarly, you can call axes.point_to_coords, or axes.p2c
# print(axes.p2c(dot.get_center()))
# We can draw lines from the axes to better mark the coordinates
# of a given point.
# Here, the always_redraw command means that on each new frame
# the lines will be redrawn
h_line = always_redraw(lambda: axes.get_h_line(dot.get_left()))
v_line = always_redraw(lambda: axes.get_v_line(dot.get_bottom()))
self.play(
ShowCreation(h_line),
ShowCreation(v_line),
)
self.play(dot.animate.move_to(axes.c2p(3, -2)))
self.wait()
self.play(dot.animate.move_to(axes.c2p(1, 1)))
self.wait()
# If we tie the dot to a particular set of coordinates, notice
# that as we move the axes around it respects the coordinate
# system defined by them.
f_always(dot.move_to, lambda: axes.c2p(1, 1))
self.play(
axes.animate.scale(0.75).to_corner(UL),
run_time=2,
)
self.wait()
self.play(FadeOut(VGroup(axes, dot, h_line, v_line)))
# Other coordinate systems you can play around with include
# ThreeDAxes, NumberPlane, and ComplexPlane.
GraphExample¶
GraphExample¶
class GraphExample(Scene):
def construct(self):
axes = Axes((-3, 10), (-1, 8))
axes.add_coordinate_labels()
self.play(Write(axes, lag_ratio=0.01, run_time=1))
# Axes.get_graph will return the graph of a function
sin_graph = axes.get_graph(
lambda x: 2 * math.sin(x),
color=BLUE,
)
# By default, it draws it so as to somewhat smoothly interpolate
# between sampled points (x, f(x)). If the graph is meant to have
# a corner, though, you can set use_smoothing to False
relu_graph = axes.get_graph(
lambda x: max(x, 0),
use_smoothing=False,
color=YELLOW,
)
# For discontinuous functions, you can specify the point of
# discontinuity so that it does not try to draw over the gap.
step_graph = axes.get_graph(
lambda x: 2.0 if x > 3 else 1.0,
discontinuities=[3],
color=GREEN,
)
# Axes.get_graph_label takes in either a string or a mobject.
# If it's a string, it treats it as a LaTeX expression. By default
# it places the label next to the graph near the right side, and
# has it match the color of the graph
sin_label = axes.get_graph_label(sin_graph, "\\sin(x)")
relu_label = axes.get_graph_label(relu_graph, Text("ReLU"))
step_label = axes.get_graph_label(step_graph, Text("Step"), x=4)
self.play(
ShowCreation(sin_graph),
FadeIn(sin_label, RIGHT),
)
self.wait(2)
self.play(
ReplacementTransform(sin_graph, relu_graph),
FadeTransform(sin_label, relu_label),
)
self.wait()
self.play(
ReplacementTransform(relu_graph, step_graph),
FadeTransform(relu_label, step_label),
)
self.wait()
parabola = axes.get_graph(lambda x: 0.25 * x**2)
parabola.set_stroke(BLUE)
self.play(
FadeOut(step_graph),
FadeOut(step_label),
ShowCreation(parabola)
)
self.wait()
# You can use axes.input_to_graph_point, abbreviated
# to axes.i2gp, to find a particular point on a graph
dot = Dot(color=RED)
dot.move_to(axes.i2gp(2, parabola))
self.play(FadeIn(dot, scale=0.5))
# A value tracker lets us animate a parameter, usually
# with the intent of having other mobjects update based
# on the parameter
x_tracker = ValueTracker(2)
f_always(
dot.move_to,
lambda: axes.i2gp(x_tracker.get_value(), parabola)
)
self.play(x_tracker.animate.set_value(4), run_time=3)
self.play(x_tracker.animate.set_value(-2), run_time=3)
self.wait()
SurfaceExample¶
SurfaceExample¶
class SurfaceExample(Scene):
CONFIG = {
"camera_class": ThreeDCamera,
}
def construct(self):
surface_text = Text("For 3d scenes, try using surfaces")
surface_text.fix_in_frame()
surface_text.to_edge(UP)
self.add(surface_text)
self.wait(0.1)
torus1 = Torus(r1=1, r2=1)
torus2 = Torus(r1=3, r2=1)
sphere = Sphere(radius=3, resolution=torus1.resolution)
# You can texture a surface with up to two images, which will
# be interpreted as the side towards the light, and away from
# the light. These can be either urls, or paths to a local file
# in whatever you've set as the image directory in
# the custom_config.yml file
# day_texture = "EarthTextureMap"
# night_texture = "NightEarthTextureMap"
day_texture = "https://upload.wikimedia.org/wikipedia/commons/thumb/4/4d/Whole_world_-_land_and_oceans.jpg/1280px-Whole_world_-_land_and_oceans.jpg"
night_texture = "https://upload.wikimedia.org/wikipedia/commons/thumb/b/ba/The_earth_at_night.jpg/1280px-The_earth_at_night.jpg"
surfaces = [
TexturedSurface(surface, day_texture, night_texture)
for surface in [sphere, torus1, torus2]
]
for mob in surfaces:
mob.shift(IN)
mob.mesh = SurfaceMesh(mob)
mob.mesh.set_stroke(BLUE, 1, opacity=0.5)
# Set perspective
frame = self.camera.frame
frame.set_euler_angles(
theta=-30 * DEGREES,
phi=70 * DEGREES,
)
surface = surfaces[0]
self.play(
FadeIn(surface),
ShowCreation(surface.mesh, lag_ratio=0.01, run_time=3),
)
for mob in surfaces:
mob.add(mob.mesh)
surface.save_state()
self.play(Rotate(surface, PI / 2), run_time=2)
for mob in surfaces[1:]:
mob.rotate(PI / 2)
self.play(
Transform(surface, surfaces[1]),
run_time=3
)
self.play(
Transform(surface, surfaces[2]),
# Move camera frame during the transition
frame.animate.increment_phi(-10 * DEGREES),
frame.animate.increment_theta(-20 * DEGREES),
run_time=3
)
# Add ambient rotation
frame.add_updater(lambda m, dt: m.increment_theta(-0.1 * dt))
# Play around with where the light is
light_text = Text("You can move around the light source")
light_text.move_to(surface_text)
light_text.fix_in_frame()
self.play(FadeTransform(surface_text, light_text))
light = self.camera.light_source
self.add(light)
light.save_state()
self.play(light.animate.move_to(3 * IN), run_time=5)
self.play(light.animate.shift(10 * OUT), run_time=5)
drag_text = Text("Try moving the mouse while pressing d or s")
drag_text.move_to(light_text)
drag_text.fix_in_frame()
self.play(FadeTransform(light_text, drag_text))
self.wait()
This scene shows an example of using a three-dimensional surface, and the related usage has been briefly described in the notes.
.fix_in_frame()makes the object not change with the view angle of the screen, and is always displayed at a fixed position on the screen.
OpeningManimExample¶
OpeningManimExample¶
class OpeningManimExample(Scene):
def construct(self):
intro_words = Text("""
The original motivation for manim was to
better illustrate mathematical functions
as transformations.
""")
intro_words.to_edge(UP)
self.play(Write(intro_words))
self.wait(2)
# Linear transform
grid = NumberPlane((-10, 10), (-5, 5))
matrix = [[1, 1], [0, 1]]
linear_transform_words = VGroup(
Text("This is what the matrix"),
IntegerMatrix(matrix, include_background_rectangle=True),
Text("looks like")
)
linear_transform_words.arrange(RIGHT)
linear_transform_words.to_edge(UP)
linear_transform_words.set_stroke(BLACK, 10, background=True)
self.play(
ShowCreation(grid),
FadeTransform(intro_words, linear_transform_words)
)
self.wait()
self.play(grid.animate.apply_matrix(matrix), run_time=3)
self.wait()
# Complex map
c_grid = ComplexPlane()
moving_c_grid = c_grid.copy()
moving_c_grid.prepare_for_nonlinear_transform()
c_grid.set_stroke(BLUE_E, 1)
c_grid.add_coordinate_labels(font_size=24)
complex_map_words = TexText("""
Or thinking of the plane as $\\mathds{C}$,\\\\
this is the map $z \\rightarrow z^2$
""")
complex_map_words.to_corner(UR)
complex_map_words.set_stroke(BLACK, 5, background=True)
self.play(
FadeOut(grid),
Write(c_grid, run_time=3),
FadeIn(moving_c_grid),
FadeTransform(linear_transform_words, complex_map_words),
)
self.wait()
self.play(
moving_c_grid.animate.apply_complex_function(lambda z: z**2),
run_time=6,
)
self.wait(2)
This scene is a comprehensive application of a two-dimensional scene.
After seeing these scenes, you have already understood part of the usage of manim. For more examples, see the video code of 3b1b.