init

2026-02-12 23:22:11 +08:00
parent 7b09eb3d89
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+"""Wrap :vtk:`vtkFollower` module."""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+from . import _vtk
+from .actor import Actor
+
+if TYPE_CHECKING:
+    from ._property import Property
+    from .camera import Camera
+    from .mapper import _BaseMapper
+
+
+class Follower(Actor, _vtk.vtkFollower):
+    """Wrap :vtk:`vtkFollower`.
+
+    A Follower is a subclass of Actor that always faces the camera. It
+    is useful for screen-aligned labels and billboarding effects.
+
+    The Follower maintains the position and scale of the actor but updates
+    its orientation continuously to face the camera.
+
+    Parameters
+    ----------
+    mapper : pyvista.DataSetMapper, optional
+        DataSetMapper.
+
+    prop : pyvista.Property, optional
+        Property of the actor.
+
+    name : str, optional
+        The name of this actor used when tracking on a plotter.
+
+    Examples
+    --------
+    Create a scene with a Follower text that always faces the camera and a transparent cube.
+
+    >>> import pyvista as pv
+    >>> from pyvista import examples
+    >>> plotter = pv.Plotter()
+
+    Create the "Hello" text that will follow the camera.
+
+    >>> text_mesh = pv.Text3D('Hello', depth=0.1)
+    >>> text_mesh = text_mesh.translate(
+    ...     [-text_mesh.center[0], -text_mesh.center[1], 0]
+    ... )
+
+    Create mapper and follower actor for the text.
+
+    >>> text_mapper = pv.DataSetMapper(text_mesh)
+    >>> follower = pv.Follower(mapper=text_mapper)
+    >>> follower.prop.color = 'gold'
+    >>> _ = plotter.add_actor(follower)
+
+    Create a transparent cube that doesn't follow the camera.
+
+    >>> cube = pv.Cube()
+    >>> cube_actor = plotter.add_mesh(
+    ...     cube, color='MidnightBlue', opacity=0.3, show_edges=False
+    ... )
+
+    Set the follower's camera and show the scene.
+
+    >>> follower.camera = plotter.camera
+    >>> plotter.show()
+
+    """
+
+    def __init__(
+        self,
+        mapper: _BaseMapper | None = None,
+        prop: Property | None = None,
+        name: str | None = None,
+    ) -> None:
+        """Initialize follower."""
+        super().__init__(mapper=mapper, prop=prop, name=name)
+
+    @property
+    def camera(self) -> Camera | None:  # numpydoc ignore=RT01
+        """Return or set the camera of this follower.
+
+        The follower will continuously update its orientation to face this camera.
+
+        """
+        return self.GetCamera()  # type: ignore[return-value]
+
+    @camera.setter
+    def camera(self, cam: Camera) -> None:
+        self.SetCamera(cam)