movement

class janim.anims.movement.Homotopy(item: Item, homotopy: Callable[[float, float, float, float], Vect], *, duration: float = 3.0, root_only: bool = False, **kwargs)

基类：DataUpdater

一个从 (x, y, z, t) 到 (x’, y’, z’) 的函数

t 的取值范围是 [0, 1]，表示动画进度

HomotopyExample

from janim.imports import *

class HomotopyExample(Timeline):
    def construct(self):
        def homotopy_func(x, y, z, t):
            return [x * t, y * t, z]

        square = Square()
        self.play(Homotopy(square, homotopy_func))
        self.forward(0.3)

class janim.anims.movement.ComplexHomotopy(item: Item, complex_homotopy: Callable[[complex, float], complex], **kwargs)

基类：Homotopy

与 Homotopy 类似，区别是用复数描述坐标

ComplexHomotopyExample

from janim.imports import *

class ComplexHomotopyExample(Timeline):
    def construct(self):
        def complex_func(z: complex, t: float) -> complex:
            return interpolate(z, z**3, t)

        group = Group(
            Text('Text'),
            Square(side_length=1),
        )
        group.points.arrange(RIGHT, buff=2)

        self.play(
            *[ComplexHomotopy(
                item,
                complex_func
            ) for item in group]
        )
        self.forward(0.3)

class janim.anims.movement.MoveAlongPath(item: Item, path: VItem, *, root_only: bool = False, **kwargs)

基类：DataUpdater

MoveAlongPathExample

from janim.imports import *

class MoveAlongPathExample(Timeline):
    def construct(self):
        line = Line(ORIGIN, RIGHT * Config.get.frame_width, buff=1)
        dot1 = Dot(color=YELLOW)

        curve = ParametricCurve(
            lambda t: [math.cos(t) * t * 0.2, math.sin(t) * t * 0.2, 0],
            (0, 10, 0.1)
        )
        dot2 = Dot(color=YELLOW)

        group = Group(line, curve).show()
        group.points.arrange(DOWN)

        self.play(
            MoveAlongPath(dot1, line),
            MoveAlongPath(dot2, curve),
            duration=2
        )
        self.forward(0.3)

class janim.anims.movement.Follow(item: Points, other: Item, direction: Vect = array([1., 0., 0.]), buff: float = 0.25, aligned_edge: Vect = array([0., 0., 0.]), coor_mask: Iterable = (1, 1, 1), item_root_only: bool = False, **kwargs)

基类：GroupUpdater[Points]

FollowExample

from janim.imports import *

class FollowExample(Timeline):
    def construct(self):
        dot = Dot(RIGHT * 2).show()
        txt = Text('dot').show()
        txt.points.next_to(dot, DOWN)

        self.forward()
        self.play(
            Succession(
                Rotate(dot, PI * 3 / 2, about_point=ORIGIN),
                dot.anim.points.shift(UP * 4),
                duration=3
            ),
            Follow(txt, dot, DOWN, duration=3),
        )
        self.forward()