Issue with ThreeDScene plus MathTex layout changing

[balopat]

I want to display MathTex in front of a 3D scene that changes significantly throughout the animation. It seems that manim can't handle it - the rendered TeX seems to fall apart. What am I missing? I am using Manim Community v0.19.2.

from manim import *
import numpy as np
from scipy.linalg import fractional_matrix_power


class ReproAnimation(ThreeDScene):

    def construct(self):
        self.camera.background_color = WHITE

        radius_range = 2
        L = (
            config.frame_height + 2.5
        )  # make all axis lengths identical (pick what you like)

        axes = ThreeDAxes(
            x_range=[-radius_range, radius_range, 1],
            y_range=[-radius_range, radius_range, 1],
            z_range=[-radius_range, radius_range, 1],
            x_length=L,
            y_length=L,
            z_length=L,
            axis_config={"include_tip": True, "stroke_color": ORANGE},
        )

        time_tracker = ValueTracker(0)

        state_text = always_redraw(lambda: self.get_state_tex(time_tracker.get_value()))

        self.set_camera_orientation(phi=75 * DEGREES, theta=-45 * DEGREES)
        self.add(axes, state_text)

        self.add_fixed_in_frame_mobjects(state_text)
        self.add_fixed_orientation_mobjects(state_text)
        total_duration = 0.5
        self.play(
            time_tracker.animate.set_value(total_duration),
            run_time=total_duration,
            rate_func=linear,
        )

    def format_complex_number(self, z):
        im_zero = np.isclose(z.imag, 0, atol=1e-3)
        imag_sign = "+" if z.imag >= 0 else "-"
        re_zero = np.isclose(z.real, 0, atol=1e-3)
        real_sign = "+" if z.real >= 0 else "-"

        if im_zero and re_zero:
            return f"0", "+"
        elif im_zero:
            return f"{z.real:.2f}", real_sign
        elif re_zero:
            return f"{z.imag:.2f}i", imag_sign
        else:
            return f"({z.real:.2f}{imag_sign}{abs(z.imag):.2f}i)", real_sign

    def get_state_tex(self, t):
        alpha, beta = self.get_qubit_state_math(t)
        alpha_str, _ = self.format_complex_number(alpha)
        beta_str, beta_sign = self.format_complex_number(beta)
        zero_str = "" if alpha_str == "0" else rf"{alpha_str} |0\rangle"
        one_str = "" if beta_str == "0" else rf"{beta_str}|1\rangle"

        superposition_str = f"{zero_str} {beta_sign if one_str and zero_str else ''} {one_str}"        

        tex = MathTex(
            rf"|\psi\rangle = {superposition_str}",
            color=BLACK,
            font_size=36,
        ).move_to(DOWN * 6)
        return tex

    def get_qubit_state_math(self, t):
        state0 = np.array([1.0 + 0.0j, 0.0 + 0.0j])  # |0>
        X = np.array([[0, 1], [1, 0]], dtype=complex)
        s = np.clip(t, 0.0, 1.0)
        X_frac = fractional_matrix_power(X, s)
        state = X_frac @ state0

        return state

ReproAnimation.mp4

[balopat]

Note, the same code renders nicely in a regular Scene.

ReproAnimation.mp4

[balopat]

If I pad the string to the same number of non-invisible characters, then it renders perfectly.

...
       full_str = rf"|\psi\rangle = {superposition_str}"

       padding_chars = "." * ((100 - len(full_str)) // 2)
       padded_str = rf"{padding_chars}{full_str}{padding_chars}"
       tex = MathTex(
            padded_str,
            color=BLACK,
            font_size=30,
        ).move_to(DOWN * 6)
...

ReproAnimation.mp4

This starts to feel like a rendering bug in manim.

[balopat]

Alright, padding with white (same color as background) dots seems to work now...

        padding_chars = "." * ((100 - len(full_str)) // 2)
        # Use textcolor with custom template that includes xcolor
        padded_str = rf"\textcolor{{white}}{{{padding_chars}}}{full_str}\textcolor{{white}}{{{padding_chars}}}"

        # Create custom TexTemplate with xcolor package
        custom_template = TexTemplate()
        custom_template.add_to_preamble(r"\usepackage{xcolor}")

        tex = MathTex(
            padded_str,
            color=BLACK,
            font_size=30,
            tex_template=custom_template,
        ).move_to(DOWN * 6)
        return tex

ReproAnimation.mp4