example_scenes.py

from manimlib.imports import *

# To watch one of these scenes, run the following:
# python -m manim example_scenes.py SquareToCircle
# Use -s to skip to the end and just save the final frame
# Use -w to write the animation to a file
# Use -o to write it to a file and open it once done
# Use -n <number> to skip ahead to the n'th animation of a scene.


class OpeningManimExample(Scene):
    def construct(self):
        title = TexText("This is some \\LaTeX")
        basel = Tex(
            "\\sum_{n=1}^\\infty "
            "\\frac{1}{n^2} = \\frac{\\pi^2}{6}"
        )
        VGroup(title, basel).arrange(DOWN)
        self.play(
            Write(title),
            FadeIn(basel, UP),
        )
        self.wait()

        transform_title = Text("That was a transform")
        transform_title.to_corner(UL)
        self.play(
            Transform(title, transform_title),
            LaggedStartMap(FadeOut, basel, shift=DOWN),
        )
        self.wait()

        fade_comment = Text(
            """
            You probably don't want to overuse
            Transforms, though, a simple fade often
            looks nicer.
            """,
            font_size=36,
            color=GREY_B,
        )
        fade_comment.next_to(
            transform_title, DOWN,
            buff=LARGE_BUFF,
            aligned_edge=LEFT
        )
        self.play(FadeIn(fade_comment, shift=DOWN))
        self.wait(3)

        grid = NumberPlane((-10, 10), (-5, 5))
        grid_title = Text(
            "But manim is for illustrating math, not text",
        )
        grid_title.to_edge(UP)
        grid_title.add_background_rectangle()

        self.add(grid, grid_title)  # Make sure title is on top of grid
        self.play(
            FadeOut(title, shift=LEFT),
            FadeOut(fade_comment, shift=LEFT),
            FadeIn(grid_title),
            ShowCreation(grid, run_time=3, lag_ratio=0.1),
        )
        self.wait()

        matrix = [[1, 1], [0, 1]]
        linear_transform_title = VGroup(
            Text("This is what the matrix"),
            IntegerMatrix(matrix, include_background_rectangle=True),
            Text("looks like")
        )
        linear_transform_title.arrange(RIGHT)
        linear_transform_title.to_edge(UP)

        self.play(
            FadeOut(grid_title),
            FadeIn(linear_transform_title),
        )
        self.play(grid.apply_matrix, matrix, run_time=3)
        self.wait()

        grid_transform_title = Text(
            "And this is a nonlinear transformation"
        )
        grid_transform_title.set_stroke(BLACK, 5, background=True)
        grid_transform_title.to_edge(UP)
        grid.prepare_for_nonlinear_transform(100)
        self.play(
            ApplyPointwiseFunction(
                lambda p: p + np.array([np.sin(p[1]), np.sin(p[0]), 0]),
                grid,
                run_time=5,
            ),
            FadeOut(linear_transform_title),
            FadeIn(grid_transform_title),
        )
        self.wait()


class SquareToCircle(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()
        self.play(ReplacementTransform(square, circle))
        self.wait()

        # This opens an iPython termnial where you can keep writing
        # lines as if they were part of this construct method
        self.embed()
        # Try typing the following lines
        # self.play(circle.stretch, 4, {"dim": 0})
        # self.play(Rotate(circle, TAU / 4))
        # self.play(circle.shift, 2 * RIGHT, circle.scale, 0.25)
        # circle.insert_n_curves(10)
        # self.play(circle.apply_complex_function, lambda z: z**2)


class AnimatingMethods(Scene):
    def construct(self):
        grid = Tex(r"\pi").get_grid(10, 10, height=4)
        self.add(grid)

        # If you pass in a mobject method to the scene's "play" function,
        # it will apply an animation interpolating between the mobject's
        # initial state and whatever happens when you apply that method.
        # For example, calling grid.shift(2 * LEFT) would shift it two units
        # to the left, but the following line animates that motion.
        self.play(grid.shift, 2 * LEFT)
        # The same applies for any method, including those setting colors.
        self.play(grid.set_submobject_colors_by_gradient, BLUE, GREEN)
        self.play(grid.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.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.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()


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}
        )
        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()


class TexTransformExample(Scene):
    def construct(self):
        to_isolate = ["B", "C", "=", "(", ")"]
        lines = VGroup(
            # Surrounding substrings with double braces
            # will ensure that those parts are separated
            # out in the Tex.  For example, here the
            # Tex will have 5 submobjects, corresponding
            # to the strings [A^2, +, B^2, =, C^2]
            Tex("{{A^2}} + {{B^2}} = {{C^2}}"),
            Tex("{{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 both lines below are equivalent
            # to what you'd get by wrapping every instance of "B", "C"
            # "=", "(" and ")" with double braces
            Tex("{{A^2}} = (C + B)(C - B)", isolate=to_isolate),
            Tex("A = \\sqrt{(C + B)(C - B)}", isolate=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 = Tex("{{A}}^2 = (C + B)(C - B)", isolate=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()


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 thst 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.scale, 2,
            rate_func=there_and_back,
            run_time=2,
        )
        self.wait()
        self.play(
            square.set_width, 5, {"stretch": True},
            run_time=3,
        )
        self.wait()
        self.play(
            square.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)


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_defaults.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.increment_phi, -10 * DEGREES,
            frame.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.move_to, 3 * IN, run_time=5)
        self.play(light.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()


class ControlsExample(Scene):
    def setup(self):
        self.textbox = Textbox()
        self.checkbox = Checkbox()
        self.color_picker = ColorSliders()
        self.panel = ControlPanel(
            Text("Text", size=0.5), self.textbox, Line(),
            Text("Show/Hide Text", size=0.5), self.checkbox, Line(),
            Text("Color of Text", size=0.5), self.color_picker
        )
        self.add(self.panel)

    def construct(self):
        text = Text("", size=2)

        def text_updater(old_text):
            assert(isinstance(old_text, Text))
            new_text = Text(self.textbox.get_value(), size=old_text.size)
            # new_text.align_data_and_family(old_text)
            new_text.move_to(old_text)
            if self.checkbox.get_value():
                new_text.set_fill(
                    color=self.color_picker.get_picked_color(),
                    opacity=self.color_picker.get_picked_opacity()
                )
            else:
                new_text.set_opacity(0)
            old_text.become(new_text)

        text.add_updater(text_updater)

        self.add(MotionMobject(text))

        self.textbox.set_value("Manim")
        # self.wait(60)
        # self.embed()


# See https://github.com/3b1b/videos for many, many more