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132 lines
4.4 KiB
ReStructuredText
132 lines
4.4 KiB
ReStructuredText
Learning by Example
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===================
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SquareToCircle
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--------------
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``example_scenes.py`` contains simple examples that we can use to learn about manim.
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Go ahead and try out the ``SquareToCircle`` scene by running it with ``$ manim example_scenes.py SquareToCircle -p``
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in manim directory.
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.. code-block:: python
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:linenos:
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from manimlib.imports import *
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class SquareToCircle(Scene):
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def construct(self):
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circle = Circle()
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square = Square()
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square.flip(RIGHT)
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square.rotate(-3 * TAU / 8)
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circle.set_fill(PINK, opacity=0.5)
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self.play(ShowCreation(square))
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self.play(Transform(square, circle))
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self.play(FadeOut(square))
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.. raw:: html
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<video width="560" height="315" controls>
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<source src="../_static/SquareToCircle.mp4" type="video/mp4">
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</video>
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.. note::
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The flag ``-p`` plays the rendered video with default video player.
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Other frequently used flags are:
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* ``-l`` for rendering video in lower resolution (which renders faster)
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* ``-s`` to show the last frame of the video.
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Run ``manim -h`` all the available flags (``python -m manim -h`` if you installed it to a venv)
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Let's step through each line of ``SquareToCircle``
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.. code-block:: python
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:lineno-start: 3
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class SquareToCircle(Scene):
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You create videos in manim by writing :class:`~scene.scene.Scene` classes.
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Each :class:`~scene.scene.Scene` in manim is self-contained. That means everything
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you created under this scene does not exist outside the class.
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.. code-block:: python
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:lineno-start: 4
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def construct(self):
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:meth:`~scene.scene.Scene.construct` specifies what is displayed on the screen
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when the :class:`~scene.scene.Scene` is rendered to video.
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.. code-block:: python
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:lineno-start: 5
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circle = Circle()
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square = Square()
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``Circle()`` and ``Square()`` create :class:`~mobject.geometry.Circle` and :class:`~mobject.geometry.Square`.
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Both of these are instances of :class:`~mobject.mobject.Mobject` subclasses, the base class for objects in manim. Note
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that instantiating a :class:`~mobject.mobject.Mobject` does not add it to the
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:class:`~scene.scene.Scene`, so you wouldn't see anything if you were to render
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the :class:`~scene.scene.Scene` at this point.
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.. code-block:: python
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:lineno-start: 7
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square.flip(RIGHT)
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square.rotate(-3 * TAU / 8)
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circle.set_fill(PINK, opacity=0.5)
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``flip()`` ``rotate()`` ``set_fill()`` apply various modifications to the mobjects before animating
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them. The call to :meth:`~mobject.mobject.Mobject.flip` flips the
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:class:`~mobject.geometry.Square` across the RIGHT vector. This is equivalent
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to a refection across the x-axis.
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The call to :meth:`~mobject.mobject.Mobject.rotate` rotates the
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:class:`~mobject.geometry.Square` 3/8ths of a full rotation counterclockwise.
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The call to :meth:`~mobject.mobject.Mobject.set_fill` sets
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the fill color for the :class:`~mobject.geometry.Circle` to pink, and its opacity to 0.5.
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.. code-block:: python
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:lineno-start: 11
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self.play(ShowCreation(square))
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self.play(Transform(square, circle))
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self.play(FadeOut(square))
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To generated animation, :class:`~animation.animation.Animation` classes are used.
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Each :class:`~animation.animation.Animation` takes one or more :class:`~mobject.mobject.Mobject` instances as arguments, which it animates
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when passed to :meth:`~scene.scene.Scene.play`. This is how video is typically
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created in manim.
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:class:`~mobject.mobject.Mobject` instances are automatically
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added to the :class:`~scene.scene.Scene` when they are animated. You can add a
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:class:`~mobject.mobject.Mobject` to the :class:`~scene.scene.Scene` manually
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by passing it as an argument to :meth:`~scene.scene.Scene.add`.
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:class:`~animation.creation.ShowCreation` draws a :class:`~mobject.mobject.Mobject` to the screen.
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:class:`~animation.transform.Transform` morphs one :class:`~mobject.mobject.Mobject` into another.
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:class:`~animation.creation.FadeOut` fades a :class:`~mobject.mobject.Mobject` out of the :class:`~scene.scene.Scene`.
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.. note::
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Only the first argument to :class:`~animation.transform.Transform` is modified,
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the second is not added to the :class:`~scene.scene.Scene`. :class:`~animation.tranform.Transform`
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only changes the appearance but not the underlying properties.
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After the call to ``transform()`` ``square`` is still a :class:`~mobject.geometry.Square` instance
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but with the shape of :class:`~mobject.geometry.Circle`.
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