[3D objects face camera] Lets objects automatically face the camera. #manim #3D #threedscene #updater

20260806_look.py

from manim import *
from scipy.spatial.transform import Rotation as Rot

class look_to_camera(ThreeDScene):
    def construct(self):
        ax = ThreeDAxes()
        self.add(ax)
        obj = VGroup(
            Text("Hello world!"),
            Line(ORIGIN, OUT, stroke_width=0, stroke_opacity=0),
            Line(ORIGIN, RIGHT, stroke_width=0, stroke_opacity=0)
        )

        def obj_updater(mobj):
            cam_rot_imatrix = np.linalg.inv(self.camera.generate_rotation_matrix())
            cam_out = np.matmul(cam_rot_imatrix, OUT)
            align_out, rssd = Rot.align_vectors(cam_out, obj[-2].get_end()-obj[-2].get_start())

            obj.apply_matrix(align_out.as_matrix())

            cam_right = np.matmul(cam_rot_imatrix, RIGHT)
            align_right, rssd = Rot.align_vectors(cam_right, obj[-1].get_end()-obj[-1].get_start())

            obj.apply_matrix(align_right.as_matrix())

        obj.add_updater(obj_updater)

        self.add(obj)

        self.wait()
        self.move_camera(
            phi = 75 * DEGREES, theta = 45 * DEGREES,
            run_time=3
        )
        self.wait()
        self.play(
            Rotate(obj[0], PI, axis=obj[-2].get_end()-obj[-2].get_start()),
            run_time=3
        )
        self.wait()

readme.md