[Text animation] Text sliding up letter by letter. #manim #text #animation

20240731_slidingtext.py

# https://discord.com/channels/581738731934056449/1268142621180690483/1268142621180690483
from manim import *

class SlideUpLetterByLetter(Animation):
    def __init__(
        self,
        text: Text,
        lag: float=0.4,
        buff: float = 0.0,
        **kwargs,
    ) -> None:
        self.lag = lag # lag between neighboring chars
        self.slope = 1/(1+(len(text)-1)*self.lag) # normalized time per transition
        self.text = text
        self.rect = SurroundingRectangle(text, fill_opacity=1, stroke_width=0, color=text.get_color(),buff=buff)
        self.bottom = self.rect.get_bottom()[1]
        self.deltay = text.get_top()[1]-self.bottom
        text.shift(self.deltay*DOWN)
        self.obj = text.copy()
        super().__init__(self.obj, **kwargs)

    def interpolate_mobject(self, alpha: float) -> None:
        dummy = self.text.copy()
        for i, letter in enumerate(dummy):
            individual_alpha = (alpha/self.slope-i*self.lag)
            individual_alpha = min(1, max(0, individual_alpha))
            letter.shift((self.deltay * rate_functions.smoothstep(individual_alpha))*UP)
            letter.become(Intersection(self.rect,letter, fill_opacity=1, stroke_width=0))
        self.obj.become(dummy)

class SlideUpExample(Scene):
    def construct(self):
        text = Tex("Hello World!").scale(2).shift(2*UP)
        self.play(SlideUpLetterByLetter(text[0], lag=0.7, buff=1), run_time=4)
        eqn = MathTex(r"x_{1,2}=-\frac{p}{2}\pm\sqrt{\frac{p^2}{4}-q}").scale(2).shift(DOWN)
        self.play(SlideUpLetterByLetter(eqn[0], lag=0.2), run_time=4)
        self.wait()

class SlideDownLetterByLetter(Animation):
    def __init__(
        self,
        text: MathTex,
        lag: float = 0.4,
        buff: float = 0.0,
        **kwargs,
    ) -> None:
        self.lag = lag  # lag between neighboring chars
        self.slope = 1 / (1 + (len(text) - 1) * self.lag)  # normalized time per transition
        self.text = text
        self.rect = SurroundingRectangle(text, fill_opacity=1, stroke_width=0, color=text.get_color(), buff=buff)
        self.top = text.get_top()[1]
        self.deltay = self.top - self.rect.get_bottom()[1]
        self.obj = text.copy()
        super().__init__(self.obj, **kwargs)

    def interpolate_mobject(self, alpha: float) -> None:
        dummy = self.text.copy()
        for i, letter in enumerate(dummy):
            individual_alpha = (alpha / self.slope - (len(dummy) - 1 - i) * self.lag)
            individual_alpha = min(1, max(0, individual_alpha))
            letter.shift((self.deltay * rate_functions.smoothstep(individual_alpha)) * DOWN)
            letter.become(Intersection(self.rect,letter, fill_opacity=1, stroke_width=0))
        self.obj.become(dummy)

class SlideDownExample(Scene):
    def construct(self):
        text = MathTex(r"1000000000000000").scale(2).shift(2*UP)
        self.wait(0.3)
        self.play(SlideDownLetterByLetter(text[0], lag=0.3, buff=1), run_time=1)
        self.wait()

readme.md