From 70584d38c51a8009deb5280bda22934c00915f5e Mon Sep 17 00:00:00 2001
From: maharshigor <gor.maharshi@gmail.com>
Date: Thu, 19 Dec 2024 00:35:55 +0530
Subject: [PATCH] RF: Uncommented the animation sections and imports

---
 fury/__init__.pyi           |   48 +-
 fury/animation/__init__.py  |    4 +-
 fury/animation/__init__.pyi |   98 +-
 fury/animation/animation.py | 2904 +++++++++++++++++------------------
 4 files changed, 1525 insertions(+), 1529 deletions(-)

diff --git a/fury/__init__.pyi b/fury/__init__.pyi
index 1fed97558..ddd86e647 100644
--- a/fury/__init__.pyi
+++ b/fury/__init__.pyi
@@ -7,7 +7,7 @@
 __all__ = [
     #     "actor",
     #     "actors",
-    #     "animation",
+    "animation",
     "colormap",
     # "convert",
     "data",
@@ -37,7 +37,7 @@ __all__ = [
 
 from . import (
     #     actors,
-    #     animation,
+    animation,
     colormap,
     #     convert,
     data,
@@ -121,28 +121,28 @@ from . import (
 # #     main_dir_uncertainty as main_dir_uncertainty,
 # #     tensor_ellipsoid as tensor_ellipsoid,
 # # )
-# from .animation import (
-#     Animation as Animation,
-#     Timeline as Timeline,
-#     color_interpolator as color_interpolator,
-#     cubic_bezier_interpolator as cubic_bezier_interpolator,
-#     cubic_spline_interpolator as cubic_spline_interpolator,
-#     euclidean_distances as euclidean_distances,
-#     get_next_timestamp as get_next_timestamp,
-#     get_previous_timestamp as get_previous_timestamp,
-#     get_time_tau as get_time_tau,
-#     get_timestamps_from_keyframes as get_timestamps_from_keyframes,
-#     get_values_from_keyframes as get_values_from_keyframes,
-#     hsv_color_interpolator as hsv_color_interpolator,
-#     lab_color_interpolator as lab_color_interpolator,
-#     lerp as lerp,
-#     linear_interpolator as linear_interpolator,
-#     slerp as slerp,
-#     spline_interpolator as spline_interpolator,
-#     step_interpolator as step_interpolator,
-#     tan_cubic_spline_interpolator as tan_cubic_spline_interpolator,
-#     xyz_color_interpolator as xyz_color_interpolator,
-# )
+from .animation import (
+    Animation as Animation,
+    # Timeline as Timeline,
+    color_interpolator as color_interpolator,
+    cubic_bezier_interpolator as cubic_bezier_interpolator,
+    cubic_spline_interpolator as cubic_spline_interpolator,
+    euclidean_distances as euclidean_distances,
+    get_next_timestamp as get_next_timestamp,
+    get_previous_timestamp as get_previous_timestamp,
+    get_time_tau as get_time_tau,
+    get_timestamps_from_keyframes as get_timestamps_from_keyframes,
+    get_values_from_keyframes as get_values_from_keyframes,
+    hsv_color_interpolator as hsv_color_interpolator,
+    lab_color_interpolator as lab_color_interpolator,
+    lerp as lerp,
+    linear_interpolator as linear_interpolator,
+    slerp as slerp,
+    spline_interpolator as spline_interpolator,
+    step_interpolator as step_interpolator,
+    tan_cubic_spline_interpolator as tan_cubic_spline_interpolator,
+    xyz_color_interpolator as xyz_color_interpolator,
+)
 from .colormap import (
     _lab2rgb as _lab2rgb,
     _lab2xyz as _lab2xyz,
diff --git a/fury/animation/__init__.py b/fury/animation/__init__.py
index adfb48395..62d86f776 100644
--- a/fury/animation/__init__.py
+++ b/fury/animation/__init__.py
@@ -1,3 +1,3 @@
-# import lazy_loader as lazy
+import lazy_loader as lazy
 
-# __getattr__, __dir__, __all__ = lazy.attach_stub(__name__, __file__)
+__getattr__, __dir__, __all__ = lazy.attach_stub(__name__, __file__)
diff --git a/fury/animation/__init__.pyi b/fury/animation/__init__.pyi
index 4544319ae..11d144e1e 100644
--- a/fury/animation/__init__.pyi
+++ b/fury/animation/__init__.pyi
@@ -1,51 +1,51 @@
-# # This file is used to enable type hinting for the `fury.animation` module.
-# # explicit definition of `__all__` will enable type inference for engines.
+# This file is used to enable type hinting for the `fury.animation` module.
+# explicit definition of `__all__` will enable type inference for engines.
 
-# __all__ = [
-#     "Animation",
-#     "CameraAnimation",
-#     # "Timeline",
-#     "euclidean_distances",
-#     "get_next_timestamp",
-#     "get_previous_timestamp",
-#     "get_time_tau",
-#     "get_timestamps_from_keyframes",
-#     "get_values_from_keyframes",
-#     "lerp",
-#     "color_interpolator",
-#     "cubic_bezier_interpolator",
-#     "cubic_spline_interpolator",
-#     "hsv_color_interpolator",
-#     "lab_color_interpolator",
-#     "linear_interpolator",
-#     "slerp",
-#     "spline_interpolator",
-#     "step_interpolator",
-#     "tan_cubic_spline_interpolator",
-#     "xyz_color_interpolator",
-# ]
+__all__ = [
+    "Animation",
+    "CameraAnimation",
+    # "Timeline",
+    "euclidean_distances",
+    "get_next_timestamp",
+    "get_previous_timestamp",
+    "get_time_tau",
+    "get_timestamps_from_keyframes",
+    "get_values_from_keyframes",
+    "lerp",
+    "color_interpolator",
+    "cubic_bezier_interpolator",
+    "cubic_spline_interpolator",
+    "hsv_color_interpolator",
+    "lab_color_interpolator",
+    "linear_interpolator",
+    "slerp",
+    "spline_interpolator",
+    "step_interpolator",
+    "tan_cubic_spline_interpolator",
+    "xyz_color_interpolator",
+]
 
-# from .animation import Animation, CameraAnimation
-# from .helpers import (
-#     euclidean_distances,
-#     get_next_timestamp,
-#     get_previous_timestamp,
-#     get_time_tau,
-#     get_timestamps_from_keyframes,
-#     get_values_from_keyframes,
-#     lerp,
-# )
-# from .interpolator import (
-#     color_interpolator,
-#     cubic_bezier_interpolator,
-#     cubic_spline_interpolator,
-#     hsv_color_interpolator,
-#     lab_color_interpolator,
-#     linear_interpolator,
-#     slerp,
-#     spline_interpolator,
-#     step_interpolator,
-#     tan_cubic_spline_interpolator,
-#     xyz_color_interpolator,
-# )
-# # from .timeline import Timeline
+from .animation import Animation, CameraAnimation
+from .helpers import (
+    euclidean_distances,
+    get_next_timestamp,
+    get_previous_timestamp,
+    get_time_tau,
+    get_timestamps_from_keyframes,
+    get_values_from_keyframes,
+    lerp,
+)
+from .interpolator import (
+    color_interpolator,
+    cubic_bezier_interpolator,
+    cubic_spline_interpolator,
+    hsv_color_interpolator,
+    lab_color_interpolator,
+    linear_interpolator,
+    slerp,
+    spline_interpolator,
+    step_interpolator,
+    tan_cubic_spline_interpolator,
+    xyz_color_interpolator,
+)
+# from .timeline import Timeline
diff --git a/fury/animation/animation.py b/fury/animation/animation.py
index 063f6ac54..22e042667 100644
--- a/fury/animation/animation.py
+++ b/fury/animation/animation.py
@@ -1,1454 +1,1450 @@
-# from collections import defaultdict
-# from time import perf_counter
-# from warnings import warn
-
-# import numpy as np
-# from scipy.spatial import transform
-
-# from fury import utils
-
-# # from fury.actor import line
-# from fury.animation.interpolator import (  # noqa F401
-#     linear_interpolator,
-#     slerp,
-#     spline_interpolator,
-#     step_interpolator,
-# )
-# from fury.decorators import warn_on_args_to_kwargs
-
-# # from fury.lib import Actor, Camera, Transform
-
-
-# class Animation:
-#     """Keyframe animation class.
-
-#     Animation is responsible for keyframe animations for a single or a
-#     group of actors.
-#     It's used to handle multiple attributes and properties of Fury actors such
-#     as transformations, color, and scale.
-#     It also accepts custom data and interpolates them, such as temperature.
-#     Linear interpolation is used by default to interpolate data between the
-#     main keyframes.
-
-#     Attributes
-#     ----------
-#     actors : Actor or list[Actor], optional, default: None
-#         Actor/s to be animated.
-#     length : float or int, default: None, optional
-#         the fixed length of the animation. If set to None, the animation will
-#         get its duration from the keyframes being set.
-#     loop : bool, optional, default: True
-#         Whether to loop the animation (True) of play once (False).
-#     motion_path_res : int, default: None
-#         the number of line segments used to visualizer the animation's motion
-#         path (visualizing position).
-
-#     """
-
-#     @warn_on_args_to_kwargs()
-#     def __init__(self, *, actors=None, length=None, loop=True, motion_path_res=None):
-#         super().__init__()
-#         self._data = defaultdict(dict)
-#         self._animations = []
-#         self._actors = []
-#         self._static_actors = []
-#         self._timeline = None
-#         self._parent_animation = None
-#         self._scene = None
-#         self._start_time = 0
-#         self._length = length
-#         self._duration = length if length else 0
-#         self._loop = loop
-#         self._current_timestamp = 0
-#         self._max_timestamp = 0
-#         self._added_to_scene = True
-#         self._motion_path_res = motion_path_res
-#         self._motion_path_actor = None
-#         self._transform = Transform()
-#         self._general_callbacks = []
-#         # Adding actors to the animation
-#         if actors is not None:
-#             self.add_actor(actors)
-
-#     def update_duration(self):
-#         """Update and return the duration of the Animation.
-
-#         Returns
-#         -------
-#         float
-#             The duration of the animation.
-
-#         """
-#         if self._length is not None:
-#             self._duration = self._length
-#         else:
-#             self._duration = max(
-#                 self._max_timestamp,
-#                 max([0] + [anim.update_duration() for anim in self.child_animations]),
-#             )
-
-#         return self.duration
-
-#     @property
-#     def duration(self):
-#         """Return the duration of the animation.
-
-#         Returns
-#         -------
-#         float
-#             The duration of the animation.
-
-#         """
-#         return self._duration
-
-#     @property
-#     def current_timestamp(self):
-#         """Return the current time of the animation.
-
-#         Returns
-#         -------
-#         float
-#             The current time of the animation.
-
-#         """
-#         if self._timeline:
-#             return self._timeline.current_timestamp
-#         elif self.parent_animation:
-#             return self.parent_animation.current_timestamp
-#         return self._current_timestamp
-
-#     def update_motion_path(self):
-#         """Update motion path visualization actor"""
-#         res = self._motion_path_res
-#         tl = self
-#         while isinstance(tl._parent_animation, Animation):
-#             if res:
-#                 break
-#             tl = tl._parent_animation
-#             res = tl._motion_path_res
-#         if not res:
-#             return
-
-#         lines = []
-#         colors = []
-#         if self.is_interpolatable("position"):
-#             ts = np.linspace(0, self.duration, res)
-#             [lines.append(self.get_position(t).tolist()) for t in ts]
-#             if self.is_interpolatable("color"):
-#                 [colors.append(self.get_color(t)) for t in ts]
-#             elif len(self._actors) >= 1:
-#                 colors = sum([i.vcolors[0] / 255 for i in self._actors]) / len(
-#                     self._actors
-#                 )
-#             else:
-#                 colors = [1, 1, 1]
-
-#         if len(lines) > 0:
-#             lines = np.array([lines])
-#             if isinstance(colors, list):
-#                 colors = np.array([colors])
-
-#             mpa = line(lines, colors=colors, opacity=0.6)
-#             if self._scene:
-#                 # remove old motion path actor
-#                 if self._motion_path_actor is not None:
-#                     self._scene.rm(self._motion_path_actor)
-#                 self._scene.add(mpa)
-#             self._motion_path_actor = mpa
-
-#     def _get_data(self):
-#         """Get animation data.
-
-#         Returns
-#         -------
-#         dict:
-#             The animation data containing keyframes and interpolators.
-
-#         """
-#         return self._data
-
-#     def _get_attribute_data(self, attrib):
-#         """Get animation data for a specific attribute.
-
-#         Parameters
-#         ----------
-#         attrib: str
-#             The attribute name to get data for.
-
-#         Returns
-#         -------
-#         dict:
-#             The animation data for a specific attribute.
-
-#         """
-#         data = self._get_data()
-
-#         if attrib not in data:
-#             data[attrib] = {
-#                 "keyframes": defaultdict(dict),
-#                 "interpolator": {
-#                     "base": (linear_interpolator if attrib != "rotation" else slerp),
-#                     "func": None,
-#                     "args": defaultdict(),
-#                 },
-#                 "callbacks": [],
-#             }
-#         return data.get(attrib)
-
-#     @warn_on_args_to_kwargs()
-#     def get_keyframes(self, *, attrib=None):
-#         """Get a keyframe for a specific or all attributes.
-
-#         Parameters
-#         ----------
-#         attrib: str, optional, default: None
-#             The name of the attribute.
-#             If None, all keyframes for all set attributes will be returned.
-
-#         """
-#         data = self._get_data()
-#         if attrib is None:
-#             attribs = data.keys()
-#             return {
-#                 attrib: data.get(
-# attrib, {}).get("keyframes", {}) for attrib in attribs
-#             }
-#         return data.get(attrib, {}).get("keyframes", {})
-
-#     @warn_on_args_to_kwargs()
-#     def set_keyframe(
-#         self, attrib, timestamp, value, *, update_interpolator=True, **kwargs
-#     ):
-#         """Set a keyframe for a certain attribute.
-
-#         Parameters
-#         ----------
-#         attrib: str
-#             The name of the attribute.
-#         timestamp: float
-#             Timestamp of the keyframe.
-#         value: ndarray or float or bool
-#             Value of the keyframe at the given timestamp.
-#         update_interpolator: bool, optional
-#             Interpolator will be reinitialized if True
-
-#         Other Parameters
-#         ----------------
-#         in_cp: ndarray, shape (1, M), optional
-#             The in control point in case of using cubic Bézier interpolator.
-#         out_cp: ndarray, shape (1, M), optional
-#             The out control point in case of using cubic Bézier interpolator.
-#         in_tangent: ndarray, shape (1, M), optional
-#             The in tangent at that position for the cubic spline curve.
-#         out_tangent: ndarray, shape (1, M), optional
-#             The out tangent at that position for the cubic spline curve.
-
-#         """
-#         attrib_data = self._get_attribute_data(attrib)
-#         keyframes = attrib_data.get("keyframes")
-
-#         keyframes[timestamp] = {
-#             "value": np.array(value).astype(float),
-#             **{
-#                 par: np.array(val).astype(float)
-#                 for par, val in kwargs.items()
-#                 if val is not None
-#             },
-#         }
-
-#         if update_interpolator:
-#             interp = attrib_data.get("interpolator")
-#             interp_base = interp.get(
-#                 "base", linear_interpolator if attrib != "rotation" else slerp
-#             )
-#             args = interp.get("args", {})
-#             self.set_interpolator(attrib, interp_base, **args)
-
-#         if timestamp > self._max_timestamp:
-#             self._max_timestamp = timestamp
-#             if self._timeline is not None:
-#                 self._timeline.update_duration()
-#             else:
-#                 self.update_duration()
-#         self.update_animation(time=0)
-#         self.update_motion_path()
-
-#     def set_keyframes(self, attrib, keyframes):
-#         """Set multiple keyframes for a certain attribute.
-
-#         Parameters
-#         ----------
-#         attrib: str
-#             The name of the attribute.
-#         keyframes: dict
-#             A dict object containing keyframes to be set.
-
-#         Notes
-#         -----
-#         Keyframes can be on any of the following forms:
-#         >>> import numpy as np
-#         >>> key_frames_simple = {1: [1, 2, 1], 2: [3, 4, 5]}
-#         >>> key_frames_bezier = {1: {'value': [1, 2, 1]},
-#         ...                      2: {'value': [3, 4, 5], 'in_cp': [1, 2, 3]}}
-#         >>> pos_keyframes = {1: np.array([1, 2, 3]), 3: np.array([5, 5, 5])}
-#         >>> Animation.set_keyframes('position', pos_keyframes) # doctest: +SKIP
-
-#         """
-#         for t, keyframe in keyframes.items():
-#             if isinstance(keyframe, dict):
-#                 self.set_keyframe(attrib, t, **keyframe)
-#             else:
-#                 self.set_keyframe(attrib, t, keyframe)
-
-#     def is_inside_scene_at(self, timestamp):
-#         """Check if the Animation is set to be inside the scene at a specific
-#         timestamp.
-
-#         Returns
-#         -------
-#         bool
-#             True if the Animation is set to be inside the scene at the given
-#             timestamp.
-
-#         Notes
-#         -----
-#         If the parent Animation is set to be out of the scene at that time, all
-#         of their child animations will be out of the scene as well.
-
-#         """
-#         parent = self._parent_animation
-#         parent_in_scene = True
-#         if parent is not None:
-#             parent_in_scene = parent._added_to_scene
-
-#         if self.is_interpolatable("in_scene"):
-#             in_scene = parent_in_scene and self.get_value("in_scene", timestamp)
-#         else:
-#             in_scene = parent_in_scene
-#         return in_scene
-
-#     def add_to_scene_at(self, timestamp):
-#         """Set timestamp for adding Animation to scene event.
-
-#         Parameters
-#         ----------
-#         timestamp: float
-#             Timestamp of the event.
-
-#         """
-#         if not self.is_interpolatable("in_scene"):
-#             self.set_keyframe("in_scene", timestamp, True)
-#             self.set_interpolator("in_scene", step_interpolator)
-#         else:
-#             self.set_keyframe("in_scene", timestamp, True)
-
-#     def remove_from_scene_at(self, timestamp):
-#         """Set timestamp for removing Animation to scene event.
-
-#         Parameters
-#         ----------
-#         timestamp: float
-#             Timestamp of the event.
-
-#         """
-#         if not self.is_interpolatable("in_scene"):
-#             self.set_keyframe("in_scene", timestamp, False)
-#             self.set_interpolator("in_scene", step_interpolator)
-#         else:
-#             self.set_keyframe("in_scene", timestamp, False)
-
-#     def _handle_scene_event(self, timestamp):
-#         should_be_in_scene = self.is_inside_scene_at(timestamp)
-#         if self._scene is not None:
-#             if should_be_in_scene and not self._added_to_scene:
-#                 self._scene.add(*self._actors)
-#                 self._added_to_scene = True
-#             elif not should_be_in_scene and self._added_to_scene:
-#                 self._scene.rm(*self._actors)
-#                 self._added_to_scene = False
-
-#     @warn_on_args_to_kwargs()
-#     def set_interpolator(self, attrib, interpolator, *, is_evaluator=False, **kwargs):
-#         """Set keyframes interpolator for a certain property
-
-#         Parameters
-#         ----------
-#         attrib: str
-#             The name of the property.
-#         interpolator: callable
-#             The generator function of the interpolator to be used to
-#             interpolate/evaluate keyframes.
-#         is_evaluator: bool, optional
-#             Specifies whether the `interpolator` is time-only based evaluation
-#             function that does not depend on keyframes such as:
-
-#             def get_position(t):
-#                 return np.array([np.sin(t), np.cos(t) * 5, 5])
-
-#         Other Parameters
-#         ----------------
-#         spline_degree: int, optional
-#             The degree of the spline in case of setting a spline interpolator.
-
-#         Notes
-#         -----
-#         If an evaluator is used to set the values of actor's properties such as
-#         position, scale, color, rotation, or opacity, it has to return a value
-#         with the same shape as the evaluated property, i.e.: for scale, it
-#         has to return an array with shape 1x3, and for opacity, it has to
-#         return a 1x1, an int, or a float value.
-
-#         Examples
-#         --------
-#         >>> Animation.set_interpolator(
-# 'position', linear_interpolator) # doctest: +SKIP
-#         >>> pos_fun = lambda t: np.array([np.sin(t), np.cos(t), 0]) # doctest: +SKIP
-#         >>> Animation.set_interpolator('position', pos_fun) # doctest: +SKIP
-
-#         """
-#         attrib_data = self._get_attribute_data(attrib)
-#         keyframes = attrib_data.get("keyframes", {})
-#         interp_data = attrib_data.get("interpolator", {})
-#         if is_evaluator:
-#             interp_data["base"] = None
-#             interp_data["func"] = interpolator
-#         else:
-#             interp_data["base"] = interpolator
-#             interp_data["args"] = kwargs
-#             # Maintain interpolator base in case new keyframes are added.
-#             if len(keyframes) == 0:
-#                 return
-#             new_interp = interpolator(keyframes, **kwargs)
-#             interp_data["func"] = new_interp
-
-#         # update motion path
-#         self.update_duration()
-#         self.update_motion_path()
-
-#     def is_interpolatable(self, attrib):
-#         """Check whether a property is interpolatable.
-
-#         Parameters
-#         ----------
-#         attrib: str
-#             The name of the property.
-
-#         Returns
-#         -------
-#         bool
-#             True if the property is interpolatable by the Animation.
-
-#         Notes
-#         -----
-#         True means that it's safe to use `Interpolator.interpolate(t)` for the
-#         specified property. And False means the opposite.
-
-#         """
-#         data = self._data
-#         return bool(data.get(attrib, {}).get("interpolator", {}).get("func"))
-
-#     @warn_on_args_to_kwargs()
-#     def set_position_interpolator(
-# self, interpolator, *, is_evaluator=False, **kwargs):
-#         """Set the position interpolator.
-
-#         Parameters
-#         ----------
-#         interpolator: callable
-#             The generator function of the interpolator that would handle the
-#              position keyframes.
-#         is_evaluator: bool, optional
-#             Specifies whether the `interpolator` is time-only based evaluation
-#             function that does not depend on keyframes.
-
-#         Other Parameters
-#         ----------------
-#         degree: int
-#             The degree of the spline interpolation in case of setting
-#             the `spline_interpolator`.
-
-#         Examples
-#         --------
-#         >>> Animation.set_position_interpolator(
-# spline_interpolator, degree=5) # doctest: +SKIP
-
-#         """  # noqa: E501
-#         self.set_interpolator(
-#             "position", interpolator, is_evaluator=is_evaluator, **kwargs
-#         )
-
-#     @warn_on_args_to_kwargs()
-#     def set_scale_interpolator(self, interpolator, *, is_evaluator=False):
-#         """Set the scale interpolator.
-
-#         Parameters
-#         ----------
-#         interpolator: callable
-#             The generator function of the interpolator that would handle
-#             the scale keyframes.
-#         is_evaluator: bool, optional
-#             Specifies whether the `interpolator` is time-only based evaluation
-#             function that does not depend on keyframes.
-
-#         Examples
-#         --------
-#         >>> Animation.set_scale_interpolator(step_interpolator) # doctest: +SKIP
-
-#         """
-#         self.set_interpolator("scale", interpolator, is_evaluator=is_evaluator)
-
-#     @warn_on_args_to_kwargs()
-#     def set_rotation_interpolator(self, interpolator, *, is_evaluator=False):
-#         """Set the rotation interpolator .
-
-#         Parameters
-#         ----------
-#         interpolator: callable
-#             The generator function of the interpolator that would handle the
-#             rotation (orientation) keyframes.
-#         is_evaluator: bool, optional
-#             Specifies whether the `interpolator` is time-only based evaluation
-#             function that does not depend on keyframes.
-
-#         Examples
-#         --------
-#         >>> Animation.set_rotation_interpolator(slerp) # doctest: +SKIP
-
-#         """
-#         self.set_interpolator("rotation", interpolator, is_evaluator=is_evaluator)
-
-#     @warn_on_args_to_kwargs()
-#     def set_color_interpolator(self, interpolator, *, is_evaluator=False):
-#         """Set the color interpolator.
-
-#         Parameters
-#         ----------
-#         interpolator: callable
-#             The generator function of the interpolator that would handle
-#             the color keyframes.
-#         is_evaluator: bool, optional
-#             Specifies whether the `interpolator` is time-only based evaluation
-#             function that does not depend on keyframes.
-
-#         Examples
-#         --------
-#         >>> Animation.set_color_interpolator(lab_color_interpolator) # doctest: +SKIP
-
-#         """
-#         self.set_interpolator("color", interpolator, is_evaluator=is_evaluator)
-
-#     @warn_on_args_to_kwargs()
-#     def set_opacity_interpolator(self, interpolator, *, is_evaluator=False):
-#         """Set the opacity interpolator.
-
-#         Parameters
-#         ----------
-#         interpolator: callable
-#             The generator function of the interpolator that would handle
-#             the opacity keyframes.
-#         is_evaluator: bool, optional
-#             Specifies whether the `interpolator` is time-only based evaluation
-#             function that does not depend on keyframes.
-
-#         Examples
-#         --------
-#         >>> Animation.set_opacity_interpolator(step_interpolator) # doctest: +SKIP
-
-#         """
-#         self.set_interpolator("opacity", interpolator, is_evaluator=is_evaluator)
-
-#     def get_value(self, attrib, timestamp):
-#         """Return the value of an attribute at any given timestamp.
-
-#         Parameters
-#         ----------
-#         attrib: str
-#             The attribute name.
-#         timestamp: float
-#             The timestamp to interpolate at.
-
-#         """
-#         value = (
-#             self._data.get(attrib, {}).get("interpolator", {}).get("func")(timestamp)
-#         )
-#         return value
-
-#     def get_current_value(self, attrib):
-#         """Return the value of an attribute at current time.
-
-#         Parameters
-#         ----------
-#         attrib: str
-#             The attribute name.
-
-#         """
-#         return (
-#             self._data.get(attrib)
-#             .get("interpolator")
-#             .get("func")(self._timeline.current_timestamp)
-#         )
-
-#     def set_position(self, timestamp, position, **kwargs):
-#         """Set a position keyframe at a specific timestamp.
-
-#         Parameters
-#         ----------
-#         timestamp: float
-#             Timestamp of the keyframe
-#         position: ndarray, shape (1, 3)
-#             Position value
-
-#         Other Parameters
-#         ----------------
-#         in_cp: float
-#             The control point in case of using `cubic Bézier interpolator` when
-#             time exceeds this timestamp.
-#         out_cp: float
-#             The control point in case of using `cubic Bézier interpolator` when
-#             time precedes this timestamp.
-#         in_tangent: ndarray, shape (1, M), optional
-#             The in tangent at that position for the cubic spline curve.
-#         out_tangent: ndarray, shape (1, M), optional
-#             The out tangent at that position for the cubic spline curve.
-
-#         Notes
-#         -----
-#         `in_cp` and `out_cp` only needed when using the cubic bezier
-#         interpolation method.
-
-#         """
-#         self.set_keyframe("position", timestamp, position, **kwargs)
-
-#     def set_position_keyframes(self, keyframes):
-#         """Set a dict of position keyframes at once.
-#         Should be in the following form:
-#         {timestamp_1: position_1, timestamp_2: position_2}
-
-#         Parameters
-#         ----------
-#         keyframes: dict
-#             A dict with timestamps as keys and positions as values.
-
-#         Examples
-#         --------
-#         >>> pos_keyframes = {1, (0, 0, 0), 3, (50, 6, 6)}
-#         >>> Animation.set_position_keyframes(pos_keyframes) # doctest: +SKIP
-
-#         """
-#         self.set_keyframes("position", keyframes)
-
-#     def set_rotation(self, timestamp, rotation, **kwargs):
-#         """Set a rotation keyframe at a specific timestamp.
-
-#         Parameters
-#         ----------
-#         timestamp: float
-#             Timestamp of the keyframe
-#         rotation: ndarray, shape(1, 3) or shape(1, 4)
-#             Rotation data in euler degrees with shape(1, 3) or in quaternions
-#             with shape(1, 4).
-
-#         Notes
-#         -----
-#         Euler rotations are executed by rotating first around Z then around X,
-#         and finally around Y.
-
-#         """
-#         no_components = len(np.array(rotation).flatten())
-#         if no_components == 4:
-#             self.set_keyframe("rotation", timestamp, rotation, **kwargs)
-#         elif no_components == 3:
-#             # user is expected to set rotation order by default as setting
-#             # orientation of a `vtkActor` ordered as z->x->y.
-#             rotation = np.asarray(rotation, dtype=float)
-#             rotation = transform.Rotation.from_euler(
-#                 "zxy", rotation[[2, 0, 1]], degrees=True
-#             ).as_quat()
-#             self.set_keyframe("rotation", timestamp, rotation, **kwargs)
-#         else:
-#             warn(
-#                 f"Keyframe with {no_components} components is not a "
-#                 f"valid rotation data. Skipped!",
-#                 stacklevel=2,
-#             )
-
-#     def set_rotation_as_vector(self, timestamp, vector, **kwargs):
-#         """Set a rotation keyframe at a specific timestamp.
-
-#         Parameters
-#         ----------
-#         timestamp: float
-#             Timestamp of the keyframe
-#         vector: ndarray, shape(1, 3)
-#             Directional vector that describes the rotation.
-
-#         """
-#         quat = transform.Rotation.from_rotvec(vector).as_quat()
-#         self.set_keyframe("rotation", timestamp, quat, **kwargs)
-
-#     def set_scale(self, timestamp, scalar, **kwargs):
-#         """Set a scale keyframe at a specific timestamp.
-
-#         Parameters
-#         ----------
-#         timestamp: float
-#             Timestamp of the keyframe
-#         scalar: ndarray, shape(1, 3)
-#             Scale keyframe value associated with the timestamp.
-
-#         """
-#         self.set_keyframe("scale", timestamp, scalar, **kwargs)
-
-#     def set_scale_keyframes(self, keyframes):
-#         """Set a dict of scale keyframes at once.
-#         Should be in the following form:
-#         {timestamp_1: scale_1, timestamp_2: scale_2}
-
-#         Parameters
-#         ----------
-#         keyframes: dict
-#             A dict with timestamps as keys and scales as values.
-
-#         Examples
-#         --------
-#         >>> scale_keyframes = {1, (1, 1, 1), 3, (2, 2, 3)}
-#         >>> Animation.set_scale_keyframes(scale_keyframes) # doctest: +SKIP
-
-#         """
-#         self.set_keyframes("scale", keyframes)
-
-#     def set_color(self, timestamp, color, **kwargs):
-#         """Set color keyframe at a specific timestamp.
-
-#         Parameters
-#         ----------
-#         timestamp: float
-#             Timestamp of the keyframe
-#         color: ndarray, shape(1, 3)
-#             Color keyframe value associated with the timestamp.
-
-#         """
-#         self.set_keyframe("color", timestamp, color, **kwargs)
-
-#     def set_color_keyframes(self, keyframes):
-#         """Set a dict of color keyframes at once.
-#         Should be in the following form:
-#         {timestamp_1: color_1, timestamp_2: color_2}
-
-#         Parameters
-#         ----------
-#         keyframes: dict
-#             A dict with timestamps as keys and color as values.
-
-#         Examples
-#         --------
-#         >>> import numpy as np
-#         >>> color_keyframes = {1, (1, 0, 1), 3, (0, 0, 1)}
-#         >>> Animation.set_color_keyframes(color_keyframes) # doctest: +SKIP
-
-#         """
-#         self.set_keyframes("color", keyframes)
-
-#     def set_opacity(self, timestamp, opacity, **kwargs):
-#         """Set opacity keyframe at a specific timestamp.
-
-#         Parameters
-#         ----------
-#         timestamp: float
-#             Timestamp of the keyframe
-#         opacity: ndarray, shape(1, 3)
-#             Opacity keyframe value associated with the timestamp.
-
-#         """
-#         self.set_keyframe("opacity", timestamp, opacity, **kwargs)
-
-#     def set_opacity_keyframes(self, keyframes):
-#         """Set a dict of opacity keyframes at once.
-#         Should be in the following form:
-#         {timestamp_1: opacity_1, timestamp_2: opacity_2}
-
-#         Parameters
-#         ----------
-#         keyframes: dict(float: ndarray, shape(1, 1) or float or int)
-#             A dict with timestamps as keys and opacities as values.
-
-#         Notes
-#         -----
-#         Opacity values should be between 0 and 1.
-
-#         Examples
-#         --------
-#         >>> opacity = {1, (1, 1, 1), 3, (2, 2, 3)}
-#         >>> Animation.set_scale_keyframes(opacity) # doctest: +SKIP
-
-#         """
-#         self.set_keyframes("opacity", keyframes)
-
-#     def get_position(self, t):
-#         """Return the interpolated position.
-
-#         Parameters
-#         ----------
-#         t: float
-#             The time to interpolate position at.
-
-#         Returns
-#         -------
-#         ndarray(1, 3):
-#             The interpolated position.
-
-#         """
-#         return self.get_value("position", t)
-
-#     def get_rotation(self, t, as_quat=False):
-#         """Return the interpolated rotation.
-
-#         Parameters
-#         ----------
-#         t: float
-#             the time to interpolate rotation at.
-#         as_quat: bool
-#             Returned rotation will be as quaternion if True.
-
-#         Returns
-#         -------
-#         ndarray(1, 3):
-#             The interpolated rotation as Euler degrees by default.
-
-#         """
-#         rot = self.get_value("rotation", t)
-#         if len(rot) == 4:
-#             if as_quat:
-#                 return rot
-#             r = transform.Rotation.from_quat(rot)
-#             degrees = r.as_euler("zxy", degrees=True)[[1, 2, 0]]
-#             return degrees
-#         elif not as_quat:
-#             return rot
-#         return transform.Rotation.from_euler(
-#             "zxy", rot[[2, 0, 1]], degrees=True
-#         ).as_quat()
-
-#     def get_scale(self, t):
-#         """Return the interpolated scale.
-
-#         Parameters
-#         ----------
-#         t: float
-#             The time to interpolate scale at.
-
-#         Returns
-#         -------
-#         ndarray(1, 3):
-#             The interpolated scale.
-
-#         """
-#         return self.get_value("scale", t)
-
-#     def get_color(self, t):
-#         """Return the interpolated color.
-
-#         Parameters
-#         ----------
-#         t: float
-#             The time to interpolate color value at.
-
-#         Returns
-#         -------
-#         ndarray(1, 3):
-#             The interpolated color.
-
-#         """
-#         return self.get_value("color", t)
-
-#     def get_opacity(self, t):
-#         """Return the opacity value.
-
-#         Parameters
-#         ----------
-#         t: float
-#             The time to interpolate opacity at.
-
-#         Returns
-#         -------
-#         ndarray(1, 1):
-#             The interpolated opacity.
-
-#         """
-#         return self.get_value("opacity", t)
-
-#     def add(self, item):
-#         """Add an item to the Animation.
-#         This item can be an Actor, Animation, list of Actors, or a list of
-#         Animations.
-
-#         Parameters
-#         ----------
-#         item: Animation, vtkActor, list[Animation], or list[vtkActor]
-#             Actor/s to be animated by the Animation.
-
-#         """
-#         if isinstance(item, list):
-#             for a in item:
-#                 self.add(a)
-#             return
-#         elif isinstance(item, Actor):
-#             self.add_actor(item)
-#         elif isinstance(item, Animation):
-#             self.add_child_animation(item)
-#         else:
-#             raise ValueError(f"Object of type {type(item)} can't be animated")
-
-#     def add_child_animation(self, animation):
-#         """Add child Animation or list of Animations.
-
-#         Parameters
-#         ----------
-#         animation: Animation or list[Animation]
-#             Animation/s to be added.
-
-#         """
-#         if isinstance(animation, list):
-#             for a in animation:
-#                 self.add_child_animation(a)
-#             return
-#         animation._parent_animation = self
-#         animation.update_motion_path()
-#         self._animations.append(animation)
-#         self.update_duration()
-
-#     @warn_on_args_to_kwargs()
-#     def add_actor(self, actor, *, static=False):
-#         """Add an actor or list of actors to the Animation.
-
-#         Parameters
-#         ----------
-#         actor: vtkActor or list(vtkActor)
-#             Actor/s to be animated by the Animation.
-#         static: bool
-#             Indicated whether the actor should be animated and controlled by
-#             the animation or just a static actor that gets added to the scene
-#             along with the Animation.
-
-#         """
-#         if isinstance(actor, list):
-#             for a in actor:
-#                 self.add_actor(a, static=static)
-#         elif static:
-#             if actor not in self.static_actors:
-#                 self._static_actors.append(actor)
-#         else:
-#             if actor not in self._actors:
-#                 actor.vcolors = utils.colors_from_actor(actor)
-#                 self._actors.append(actor)
-
-#     @property
-#     def timeline(self):
-#         """Return the Timeline handling the current animation.
-
-#         Returns
-#         -------
-#         Timeline:
-#             The Timeline handling the current animation, None, if there is no
-#             associated Timeline.
-
-#         """
-#         return self._timeline
-
-#     @timeline.setter
-#     def timeline(self, timeline):
-#         """Assign the Timeline responsible for handling the Animation.
-
-#         Parameters
-#         ----------
-#         timeline: Timeline
-#             The Timeline handling the current animation, None, if there is no
-#             associated Timeline.
-
-#         """
-#         self._timeline = timeline
-#         if self._animations:
-#             for animation in self._animations:
-#                 animation.timeline = timeline
-
-#     @property
-#     def parent_animation(self):
-#         """Return the hierarchical parent Animation for current Animation.
-
-#         Returns
-#         -------
-#         Animation:
-#             The parent Animation.
-
-#         """
-#         return self._parent_animation
-
-#     @parent_animation.setter
-#     def parent_animation(self, parent_animation):
-#         """Assign a parent Animation for the current Animation.
-
-#         Parameters
-#         ----------
-#         parent_animation: Animation
-#             The parent Animation instance.
-
-#         """
-#         self._parent_animation = parent_animation
-
-#     @property
-#     def actors(self):
-#         """Return a list of actors.
-
-#         Returns
-#         -------
-#         list:
-#             List of actors controlled by the Animation.
-
-#         """
-#         return self._actors
-
-#     @property
-#     def child_animations(self) -> "list[Animation]":
-#         """Return a list of child Animations.
-
-#         Returns
-#         -------
-#         list:
-#             List of child Animations of this Animation.
-
-#         """
-#         return self._animations
-
-#     def add_static_actor(self, actor):
-#         """Add an actor or list of actors as static actor/s which will not be
-#         controlled nor animated by the Animation. All static actors will be
-#         added to the scene when the Animation is added to the scene.
-
-#         Parameters
-#         ----------
-#         actor: vtkActor or list(vtkActor)
-#             Static actor/s.
-
-#         """
-#         self.add_actor(actor, static=True)
-
-#     @property
-#     def static_actors(self):
-#         """Return a list of static actors.
-
-#         Returns
-#         -------
-#         list:
-#             List of static actors.
-
-#         """
-#         return self._static_actors
-
-#     def remove_animations(self):
-#         """Remove all child Animations from the Animation"""
-#         self._animations.clear()
-
-#     def remove_actor(self, actor):
-#         """Remove an actor from the Animation.
-
-#         Parameters
-#         ----------
-#         actor: vtkActor
-#             Actor to be removed from the Animation.
-
-#         """
-#         self._actors.remove(actor)
-
-#     def remove_actors(self):
-#         """Remove all actors from the Animation"""
-#         self._actors.clear()
-
-#     @property
-#     def loop(self):
-#         """Get loop condition of the current animation.
-
-#         Returns
-#         -------
-#         bool
-#             Whether the animation in loop mode (True) or play one mode (False).
-
-#         """
-#         return self._loop
-
-#     @loop.setter
-#     def loop(self, loop):
-#         """Set the animation to loop or play once.
-
-#         Parameters
-#         ----------
-#         loop: bool
-#             The loop condition to be set. (True) to loop the animation, and
-#             (False) to play only once.
-
-#         """
-#         self._loop = loop
-
-#     def add_update_callback(self, callback, prop=None):
-#         """Add a function to be called each time animation is updated
-#         This function must accept only one argument which is the current value
-#         of the named property.
-
-
-#         Parameters
-#         ----------
-#         callback: callable
-#             The function to be called whenever the animation is updated.
-#         prop: str, optional, default: None
-#             The name of the property.
-
-#         Notes
-#         -----
-#         If no attribute name was provided, current time of the animation will
-#         be provided instead of current value for the callback.
-
-#         """
-#         if prop is None:
-#             self._general_callbacks.append(callback)
-#             return
-#         attrib = self._get_attribute_data(prop)
-#         attrib.get("callbacks", []).append(callback)
-
-#     @warn_on_args_to_kwargs()
-#     def update_animation(self, *, time=None):
-#         """Update the animation.
-
-#         Update the animation at a certain time. This will make sure all
-#         attributes are calculated and set to the actors at that given time.
-
-#         Parameters
-#         ----------
-#         time: float or int, optional, default: None
-#             The time to update animation at. If None, the animation will play
-#             without adding it to a Timeline.
-
-#         """
-#         has_handler = True
-#         if time is None:
-#             time = perf_counter() - self._start_time
-#             has_handler = False
-
-#         # handling in/out of scene events
-#         in_scene = self.is_inside_scene_at(time)
-#         self._handle_scene_event(time)
-
-#         if self.duration:
-#             if self._loop and time > self.duration:
-#                 time = time % self.duration
-#             elif time > self.duration:
-#                 time = self.duration
-#         if isinstance(self._parent_animation, Animation):
-#             self._transform.DeepCopy(self._parent_animation._transform)
-#         else:
-#             self._transform.Identity()
-
-#         self._current_timestamp = time
-
-#         # actors properties
-#         if in_scene:
-#             if self.is_interpolatable("position"):
-#                 position = self.get_position(time)
-#                 self._transform.Translate(*position)
-
-#             if self.is_interpolatable("opacity"):
-#                 opacity = self.get_opacity(time)
-#                 [act.GetProperty().SetOpacity(opacity) for act in self.actors]
-
-#             if self.is_interpolatable("rotation"):
-#                 x, y, z = self.get_rotation(time)
-#                 # Rotate in the same order as VTK defaults.
-#                 self._transform.RotateZ(z)
-#                 self._transform.RotateX(x)
-#                 self._transform.RotateY(y)
-
-#             if self.is_interpolatable("scale"):
-#                 scale = self.get_scale(time)
-#                 self._transform.Scale(*scale)
-
-#             if self.is_interpolatable("color"):
-#                 color = self.get_color(time)
-#                 for act in self.actors:
-#                     act.vcolors[:] = color * 255
-#                     utils.update_actor(act)
-
-#             # update actors' transformation matrix
-#             [act.SetUserTransform(self._transform) for act in self.actors]
-
-#         for attrib in self._data:
-#             callbacks = self._data.get(attrib, {}).get("callbacks", [])
-#             if callbacks != [] and self.is_interpolatable(attrib):
-#                 value = self.get_value(attrib, time)
-#                 [cbk(value) for cbk in callbacks]
-
-#         # Executing general callbacks that's not related to any attribute
-#         [callback(time) for callback in self._general_callbacks]
-
-#         # Also update all child Animations.
-#         [animation.update_animation(time=time) for animation in self._animations]
-
-#         if self._scene and not has_handler:
-#             self._scene.reset_clipping_range()
-
-#     def add_to_scene(self, scene):
-#         """Add this Animation, its actors and sub Animations to the scene"""
-#         [scene.add(actor) for actor in self._actors]
-#         [scene.add(static_act) for static_act in self._static_actors]
-#         [scene.add(animation) for animation in self._animations]
-
-#         if self._motion_path_actor:
-#             scene.add(self._motion_path_actor)
-#         self._scene = scene
-#         self._added_to_scene = True
-#         self._start_time = perf_counter()
-#         self.update_animation(time=0)
-
-#     def remove_from_scene(self, scene):
-#         """Remove Animation, its actors and sub Animations from the scene"""
-#         [scene.rm(act) for act in self.actors]
-#         [scene.rm(static_act) for static_act in self._static_actors]
-#         for anim in self.child_animations:
-#             anim.remove_from_scene(scene)
-#         if self._motion_path_actor:
-#             scene.rm(self._motion_path_actor)
-#         self._added_to_scene = False
-
-
-# class CameraAnimation(Animation):
-#     """Camera keyframe animation class.
-
-#     This is used for animating a single camera using a set of keyframes.
-
-#     Attributes
-#     ----------
-#     camera : Camera, optional, default: None
-#         Camera to be animated. If None, active camera will be animated.
-#     length : float or int, default: None, optional
-#         the fixed length of the animation. If set to None, the animation will
-#         get its duration from the keyframes being set.
-#     loop : bool, optional, default: True
-#         Whether to loop the animation (True) of play once (False).
-#     motion_path_res : int, default: None
-#         the number of line segments used to visualizer the animation's motion
-#         path (visualizing position).
-
-#     """
-
-#     @warn_on_args_to_kwargs()
-#     def __init__(self, *, camera=None, length=None, loop=True, motion_path_res=None):
-#         super(CameraAnimation, self).__init__(
-#             length=length, loop=loop, motion_path_res=motion_path_res
-#         )
-#         self._camera = camera
-
-#     @property
-#     def camera(self) -> Camera:
-#         """Return the camera assigned to this animation.
-
-#         Returns
-#         -------
-#         Camera:
-#             The camera that is being animated by this CameraAnimation.
-
-#         """
-#         return self._camera
-
-#     @camera.setter
-#     def camera(self, camera: Camera):
-#         """Set a camera to be animated.
-
-#         Parameters
-#         ----------
-#         camera: Camera
-#             The camera to be animated
-
-#         """
-#         self._camera = camera
-
-#     def set_focal(self, timestamp, position, **kwargs):
-#         """Set camera's focal position keyframe.
-
-#         Parameters
-#         ----------
-#         timestamp: float
-#             The time to interpolate opacity at.
-#         position: ndarray, shape(1, 3)
-#             The camera position
-
-#         """
-#         self.set_keyframe("focal", timestamp, position, **kwargs)
-
-#     def set_view_up(self, timestamp, direction, **kwargs):
-#         """Set the camera view-up direction keyframe.
-
-#         Parameters
-#         ----------
-#         timestamp: float
-#             The time to interpolate at.
-#         direction: ndarray, shape(1, 3)
-#             The camera view-up direction
-
-#         """
-#         self.set_keyframe("view_up", timestamp, direction, **kwargs)
-
-#     def set_focal_keyframes(self, keyframes):
-#         """Set multiple camera focal position keyframes at once.
-#         Should be in the following form:
-#         {timestamp_1: focal_1, timestamp_2: focal_1, ...}
-
-#         Parameters
-#         ----------
-#         keyframes: dict
-#             A dict with timestamps as keys and camera focal positions as
-#             values.
-
-#         Examples
-#         --------
-#         >>> focal_pos = {0, (1, 1, 1), 3, (20, 0, 0)}
-#         >>> CameraAnimation.set_focal_keyframes(focal_pos) # doctest: +SKIP
-
-#         """
-#         self.set_keyframes("focal", keyframes)
-
-#     def set_view_up_keyframes(self, keyframes):
-#         """Set multiple camera view up direction keyframes.
-#         Should be in the following form:
-#         {timestamp_1: view_up_1, timestamp_2: view_up_2, ...}
-
-#         Parameters
-#         ----------
-#         keyframes: dict
-#             A dict with timestamps as keys and camera view up vectors as
-#             values.
-
-#         Examples
-#         --------
-#         >>> view_ups = {
-# 0, np.array([1, 0, 0]), 3, np.array([0, 1, 0])} # doctest: +SKIP
-#         >>> CameraAnimation.set_view_up_keyframes(view_ups) # doctest: +SKIP
-
-#         """
-#         self.set_keyframes("view_up", keyframes)
-
-#     def get_focal(self, t):
-#         """Return the interpolated camera's focal position.
-
-#         Parameters
-#         ----------
-#         t: float
-#             The time to interpolate at.
-
-#         Returns
-#         -------
-#         ndarray(1, 3):
-#             The interpolated camera's focal position.
-
-#         Notes
-#         -----
-#         The returned focal position does not necessarily reflect the current
-#         camera's focal position, but the expected one.
-
-#         """
-#         return self.get_value("focal", t)
-
-#     def get_view_up(self, t):
-#         """Return the interpolated camera's view-up directional vector.
-
-#         Parameters
-#         ----------
-#         t: float
-#             The time to interpolate at.
-
-#         Returns
-#         -------
-#         ndarray(1, 3):
-#             The interpolated camera view-up directional vector.
-
-#         Notes
-#         -----
-#         The returned focal position does not necessarily reflect the actual
-#         camera view up directional vector, but the expected one.
-
-#         """
-#         return self.get_value("view_up", t)
-
-#     @warn_on_args_to_kwargs()
-#     def set_focal_interpolator(self, interpolator, *, is_evaluator=False):
-#         """Set the camera focal position interpolator.
-
-#         Parameters
-#         ----------
-#         interpolator: callable
-#             The generator function of the interpolator that would handle the
-#             interpolation of the camera focal position keyframes.
-#         is_evaluator: bool, optional
-#             Specifies whether the `interpolator` is time-only based evaluation
-#             function that does not depend on keyframes.
-
-#         """
-#         self.set_interpolator("focal", interpolator, is_evaluator=is_evaluator)
-
-#     @warn_on_args_to_kwargs()
-#     def set_view_up_interpolator(self, interpolator, *, is_evaluator=False):
-#         """Set the camera up-view vector animation interpolator.
-
-#         Parameters
-#         ----------
-#         interpolator: callable
-#             The generator function of the interpolator that would handle the
-#             interpolation of the camera view-up keyframes.
-#         is_evaluator: bool, optional
-#             Specifies whether the `interpolator` is time-only based evaluation
-#             function that does not depend on keyframes.
-
-#         """
-#         self.set_interpolator("view_up", interpolator, is_evaluator=is_evaluator)
-
-#     @warn_on_args_to_kwargs()
-#     def update_animation(self, *, time=None):
-#         """Update the camera animation.
-
-#         Parameters
-#         ----------
-#         time: float or int, optional, default: None
-#             The time to update the camera animation at. If None, the animation
-#             will play.
-
-#         """
-#         if self._camera is None:
-#             if self._scene:
-#                 self._camera = self._scene.camera()
-#                 self.update_animation(tile=time)
-#                 return
-#         else:
-#             if self.is_interpolatable("rotation"):
-#                 pos = self._camera.GetPosition()
-#                 translation = np.identity(4)
-#                 translation[:3, 3] = pos
-#                 # camera axis is reverted
-#                 rot = -self.get_rotation(time, as_quat=True)
-#                 rot = transform.Rotation.from_quat(rot).as_matrix()
-#                 rot = np.array(
-# [[*rot[0], 0], [*rot[1], 0], [*rot[2], 0], [0, 0, 0, 1]])
-#                 rot = translation @ rot @ np.linalg.inv(translation)
-#                 self._camera.SetModelTransformMatrix(rot.flatten())
-
-#             if self.is_interpolatable("position"):
-#                 cam_pos = self.get_position(time)
-#                 self._camera.SetPosition(cam_pos)
-
-#             if self.is_interpolatable("focal"):
-#                 cam_foc = self.get_focal(time)
-#                 self._camera.SetFocalPoint(cam_foc)
-
-#             if self.is_interpolatable("view_up"):
-#                 cam_up = self.get_view_up(time)
-#                 self._camera.SetViewUp(cam_up)
-#             elif not self.is_interpolatable("view_up"):
-#                 # to preserve up-view as default after user interaction
-#                 self._camera.SetViewUp(0, 1, 0)
-#             if self._scene:
-#                 self._scene.reset_clipping_range()
+from collections import defaultdict
+from time import perf_counter
+from warnings import warn
+
+import numpy as np
+from scipy.spatial import transform
+
+from fury import utils
+
+# from fury.actor import line
+from fury.animation.interpolator import (  # noqa F401
+    linear_interpolator,
+    slerp,
+    spline_interpolator,
+    step_interpolator,
+)
+from fury.decorators import warn_on_args_to_kwargs
+
+# from fury.lib import Actor, Camera, Transform
+
+
+class Animation:
+    """Keyframe animation class.
+
+    Animation is responsible for keyframe animations for a single or a
+    group of actors.
+    It's used to handle multiple attributes and properties of Fury actors such
+    as transformations, color, and scale.
+    It also accepts custom data and interpolates them, such as temperature.
+    Linear interpolation is used by default to interpolate data between the
+    main keyframes.
+
+    Attributes
+    ----------
+    actors : Actor or list[Actor], optional, default: None
+        Actor/s to be animated.
+    length : float or int, default: None, optional
+        the fixed length of the animation. If set to None, the animation will
+        get its duration from the keyframes being set.
+    loop : bool, optional, default: True
+        Whether to loop the animation (True) of play once (False).
+    motion_path_res : int, default: None
+        the number of line segments used to visualizer the animation's motion
+        path (visualizing position).
+
+    """
+
+    @warn_on_args_to_kwargs()
+    def __init__(self, *, actors=None, length=None, loop=True, motion_path_res=None):
+        super().__init__()
+        self._data = defaultdict(dict)
+        self._animations = []
+        self._actors = []
+        self._static_actors = []
+        self._timeline = None
+        self._parent_animation = None
+        self._scene = None
+        self._start_time = 0
+        self._length = length
+        self._duration = length if length else 0
+        self._loop = loop
+        self._current_timestamp = 0
+        self._max_timestamp = 0
+        self._added_to_scene = True
+        self._motion_path_res = motion_path_res
+        self._motion_path_actor = None
+        # self._transform = Transform()
+        self._general_callbacks = []
+        # Adding actors to the animation
+        if actors is not None:
+            self.add_actor(actors)
+
+    def update_duration(self):
+        """Update and return the duration of the Animation.
+
+        Returns
+        -------
+        float
+            The duration of the animation.
+
+        """
+        if self._length is not None:
+            self._duration = self._length
+        else:
+            self._duration = max(
+                self._max_timestamp,
+                max([0] + [anim.update_duration() for anim in self.child_animations]),
+            )
+
+        return self.duration
+
+    @property
+    def duration(self):
+        """Return the duration of the animation.
+
+        Returns
+        -------
+        float
+            The duration of the animation.
+
+        """
+        return self._duration
+
+    @property
+    def current_timestamp(self):
+        """Return the current time of the animation.
+
+        Returns
+        -------
+        float
+            The current time of the animation.
+
+        """
+        if self._timeline:
+            return self._timeline.current_timestamp
+        elif self.parent_animation:
+            return self.parent_animation.current_timestamp
+        return self._current_timestamp
+
+    def update_motion_path(self):
+        """Update motion path visualization actor"""
+        res = self._motion_path_res
+        tl = self
+        while isinstance(tl._parent_animation, Animation):
+            if res:
+                break
+            tl = tl._parent_animation
+            res = tl._motion_path_res
+        if not res:
+            return
+
+        lines = []
+        colors = []
+        if self.is_interpolatable("position"):
+            ts = np.linspace(0, self.duration, res)
+            [lines.append(self.get_position(t).tolist()) for t in ts]
+            if self.is_interpolatable("color"):
+                [colors.append(self.get_color(t)) for t in ts]
+            elif len(self._actors) >= 1:
+                colors = sum([i.vcolors[0] / 255 for i in self._actors]) / len(
+                    self._actors
+                )
+            else:
+                colors = [1, 1, 1]
+
+        # if len(lines) > 0:
+        #     lines = np.array([lines])
+        #     if isinstance(colors, list):
+        #         colors = np.array([colors])
+
+        #     mpa = line(lines, colors=colors, opacity=0.6)
+        #     if self._scene:
+        #         # remove old motion path actor
+        #         if self._motion_path_actor is not None:
+        #             self._scene.rm(self._motion_path_actor)
+        #         self._scene.add(mpa)
+        #     self._motion_path_actor = mpa
+
+    def _get_data(self):
+        """Get animation data.
+
+        Returns
+        -------
+        dict:
+            The animation data containing keyframes and interpolators.
+
+        """
+        return self._data
+
+    def _get_attribute_data(self, attrib):
+        """Get animation data for a specific attribute.
+
+        Parameters
+        ----------
+        attrib: str
+            The attribute name to get data for.
+
+        Returns
+        -------
+        dict:
+            The animation data for a specific attribute.
+
+        """
+        data = self._get_data()
+
+        if attrib not in data:
+            data[attrib] = {
+                "keyframes": defaultdict(dict),
+                "interpolator": {
+                    "base": (linear_interpolator if attrib != "rotation" else slerp),
+                    "func": None,
+                    "args": defaultdict(),
+                },
+                "callbacks": [],
+            }
+        return data.get(attrib)
+
+    @warn_on_args_to_kwargs()
+    def get_keyframes(self, *, attrib=None):
+        """Get a keyframe for a specific or all attributes.
+
+        Parameters
+        ----------
+        attrib: str, optional, default: None
+            The name of the attribute.
+            If None, all keyframes for all set attributes will be returned.
+
+        """
+        data = self._get_data()
+        if attrib is None:
+            attribs = data.keys()
+            return {
+                attrib: data.get(attrib, {}).get("keyframes", {}) for attrib in attribs
+            }
+        return data.get(attrib, {}).get("keyframes", {})
+
+    @warn_on_args_to_kwargs()
+    def set_keyframe(
+        self, attrib, timestamp, value, *, update_interpolator=True, **kwargs
+    ):
+        """Set a keyframe for a certain attribute.
+
+        Parameters
+        ----------
+        attrib: str
+            The name of the attribute.
+        timestamp: float
+            Timestamp of the keyframe.
+        value: ndarray or float or bool
+            Value of the keyframe at the given timestamp.
+        update_interpolator: bool, optional
+            Interpolator will be reinitialized if True
+
+        Other Parameters
+        ----------------
+        in_cp: ndarray, shape (1, M), optional
+            The in control point in case of using cubic Bézier interpolator.
+        out_cp: ndarray, shape (1, M), optional
+            The out control point in case of using cubic Bézier interpolator.
+        in_tangent: ndarray, shape (1, M), optional
+            The in tangent at that position for the cubic spline curve.
+        out_tangent: ndarray, shape (1, M), optional
+            The out tangent at that position for the cubic spline curve.
+
+        """
+        attrib_data = self._get_attribute_data(attrib)
+        keyframes = attrib_data.get("keyframes")
+
+        keyframes[timestamp] = {
+            "value": np.array(value).astype(float),
+            **{
+                par: np.array(val).astype(float)
+                for par, val in kwargs.items()
+                if val is not None
+            },
+        }
+
+        if update_interpolator:
+            interp = attrib_data.get("interpolator")
+            interp_base = interp.get(
+                "base", linear_interpolator if attrib != "rotation" else slerp
+            )
+            args = interp.get("args", {})
+            self.set_interpolator(attrib, interp_base, **args)
+
+        if timestamp > self._max_timestamp:
+            self._max_timestamp = timestamp
+            if self._timeline is not None:
+                self._timeline.update_duration()
+            else:
+                self.update_duration()
+        self.update_animation(time=0)
+        self.update_motion_path()
+
+    def set_keyframes(self, attrib, keyframes):
+        """Set multiple keyframes for a certain attribute.
+
+        Parameters
+        ----------
+        attrib: str
+            The name of the attribute.
+        keyframes: dict
+            A dict object containing keyframes to be set.
+
+        Notes
+        -----
+        Keyframes can be on any of the following forms:
+        >>> import numpy as np
+        >>> key_frames_simple = {1: [1, 2, 1], 2: [3, 4, 5]}
+        >>> key_frames_bezier = {1: {'value': [1, 2, 1]},
+        ...                      2: {'value': [3, 4, 5], 'in_cp': [1, 2, 3]}}
+        >>> pos_keyframes = {1: np.array([1, 2, 3]), 3: np.array([5, 5, 5])}
+        >>> Animation.set_keyframes('position', pos_keyframes) # doctest: +SKIP
+
+        """
+        for t, keyframe in keyframes.items():
+            if isinstance(keyframe, dict):
+                self.set_keyframe(attrib, t, **keyframe)
+            else:
+                self.set_keyframe(attrib, t, keyframe)
+
+    def is_inside_scene_at(self, timestamp):
+        """Check if the Animation is set to be inside the scene at a specific
+        timestamp.
+
+        Returns
+        -------
+        bool
+            True if the Animation is set to be inside the scene at the given
+            timestamp.
+
+        Notes
+        -----
+        If the parent Animation is set to be out of the scene at that time, all
+        of their child animations will be out of the scene as well.
+
+        """
+        parent = self._parent_animation
+        parent_in_scene = True
+        if parent is not None:
+            parent_in_scene = parent._added_to_scene
+
+        if self.is_interpolatable("in_scene"):
+            in_scene = parent_in_scene and self.get_value("in_scene", timestamp)
+        else:
+            in_scene = parent_in_scene
+        return in_scene
+
+    def add_to_scene_at(self, timestamp):
+        """Set timestamp for adding Animation to scene event.
+
+        Parameters
+        ----------
+        timestamp: float
+            Timestamp of the event.
+
+        """
+        if not self.is_interpolatable("in_scene"):
+            self.set_keyframe("in_scene", timestamp, True)
+            self.set_interpolator("in_scene", step_interpolator)
+        else:
+            self.set_keyframe("in_scene", timestamp, True)
+
+    def remove_from_scene_at(self, timestamp):
+        """Set timestamp for removing Animation to scene event.
+
+        Parameters
+        ----------
+        timestamp: float
+            Timestamp of the event.
+
+        """
+        if not self.is_interpolatable("in_scene"):
+            self.set_keyframe("in_scene", timestamp, False)
+            self.set_interpolator("in_scene", step_interpolator)
+        else:
+            self.set_keyframe("in_scene", timestamp, False)
+
+    def _handle_scene_event(self, timestamp):
+        should_be_in_scene = self.is_inside_scene_at(timestamp)
+        if self._scene is not None:
+            if should_be_in_scene and not self._added_to_scene:
+                self._scene.add(*self._actors)
+                self._added_to_scene = True
+            elif not should_be_in_scene and self._added_to_scene:
+                self._scene.rm(*self._actors)
+                self._added_to_scene = False
+
+    @warn_on_args_to_kwargs()
+    def set_interpolator(self, attrib, interpolator, *, is_evaluator=False, **kwargs):
+        """Set keyframes interpolator for a certain property
+
+        Parameters
+        ----------
+        attrib: str
+            The name of the property.
+        interpolator: callable
+            The generator function of the interpolator to be used to
+            interpolate/evaluate keyframes.
+        is_evaluator: bool, optional
+            Specifies whether the `interpolator` is time-only based evaluation
+            function that does not depend on keyframes such as:
+
+            def get_position(t):
+                return np.array([np.sin(t), np.cos(t) * 5, 5])
+
+        Other Parameters
+        ----------------
+        spline_degree: int, optional
+            The degree of the spline in case of setting a spline interpolator.
+
+        Notes
+        -----
+        If an evaluator is used to set the values of actor's properties such as
+        position, scale, color, rotation, or opacity, it has to return a value
+        with the same shape as the evaluated property, i.e.: for scale, it
+        has to return an array with shape 1x3, and for opacity, it has to
+        return a 1x1, an int, or a float value.
+
+        Examples
+        --------
+        >>> Animation.set_interpolator('position', linear_interpolator) # doctest: +SKIP
+        >>> pos_fun = lambda t: np.array([np.sin(t), np.cos(t), 0]) # doctest: +SKIP
+        >>> Animation.set_interpolator('position', pos_fun) # doctest: +SKIP
+
+        """
+        attrib_data = self._get_attribute_data(attrib)
+        keyframes = attrib_data.get("keyframes", {})
+        interp_data = attrib_data.get("interpolator", {})
+        if is_evaluator:
+            interp_data["base"] = None
+            interp_data["func"] = interpolator
+        else:
+            interp_data["base"] = interpolator
+            interp_data["args"] = kwargs
+            # Maintain interpolator base in case new keyframes are added.
+            if len(keyframes) == 0:
+                return
+            new_interp = interpolator(keyframes, **kwargs)
+            interp_data["func"] = new_interp
+
+        # update motion path
+        self.update_duration()
+        self.update_motion_path()
+
+    def is_interpolatable(self, attrib):
+        """Check whether a property is interpolatable.
+
+        Parameters
+        ----------
+        attrib: str
+            The name of the property.
+
+        Returns
+        -------
+        bool
+            True if the property is interpolatable by the Animation.
+
+        Notes
+        -----
+        True means that it's safe to use `Interpolator.interpolate(t)` for the
+        specified property. And False means the opposite.
+
+        """
+        data = self._data
+        return bool(data.get(attrib, {}).get("interpolator", {}).get("func"))
+
+    @warn_on_args_to_kwargs()
+    def set_position_interpolator(self, interpolator, *, is_evaluator=False, **kwargs):
+        """Set the position interpolator.
+
+                Parameters
+                ----------
+                interpolator: callable
+                    The generator function of the interpolator that would handle the
+                     position keyframes.
+                is_evaluator: bool, optional
+                    Specifies whether the `interpolator` is time-only based evaluation
+                    function that does not depend on keyframes.
+
+                Other Parameters
+                ----------------
+                degree: int
+                    The degree of the spline interpolation in case of setting
+                    the `spline_interpolator`.
+
+                Examples
+                --------
+                >>> Animation.set_position_interpolator(
+        spline_interpolator, degree=5) # doctest: +SKIP
+
+        """  # noqa: E501
+        self.set_interpolator(
+            "position", interpolator, is_evaluator=is_evaluator, **kwargs
+        )
+
+    @warn_on_args_to_kwargs()
+    def set_scale_interpolator(self, interpolator, *, is_evaluator=False):
+        """Set the scale interpolator.
+
+        Parameters
+        ----------
+        interpolator: callable
+            The generator function of the interpolator that would handle
+            the scale keyframes.
+        is_evaluator: bool, optional
+            Specifies whether the `interpolator` is time-only based evaluation
+            function that does not depend on keyframes.
+
+        Examples
+        --------
+        >>> Animation.set_scale_interpolator(step_interpolator) # doctest: +SKIP
+
+        """
+        self.set_interpolator("scale", interpolator, is_evaluator=is_evaluator)
+
+    @warn_on_args_to_kwargs()
+    def set_rotation_interpolator(self, interpolator, *, is_evaluator=False):
+        """Set the rotation interpolator .
+
+        Parameters
+        ----------
+        interpolator: callable
+            The generator function of the interpolator that would handle the
+            rotation (orientation) keyframes.
+        is_evaluator: bool, optional
+            Specifies whether the `interpolator` is time-only based evaluation
+            function that does not depend on keyframes.
+
+        Examples
+        --------
+        >>> Animation.set_rotation_interpolator(slerp) # doctest: +SKIP
+
+        """
+        self.set_interpolator("rotation", interpolator, is_evaluator=is_evaluator)
+
+    @warn_on_args_to_kwargs()
+    def set_color_interpolator(self, interpolator, *, is_evaluator=False):
+        """Set the color interpolator.
+
+        Parameters
+        ----------
+        interpolator: callable
+            The generator function of the interpolator that would handle
+            the color keyframes.
+        is_evaluator: bool, optional
+            Specifies whether the `interpolator` is time-only based evaluation
+            function that does not depend on keyframes.
+
+        Examples
+        --------
+        >>> Animation.set_color_interpolator(lab_color_interpolator) # doctest: +SKIP
+
+        """
+        self.set_interpolator("color", interpolator, is_evaluator=is_evaluator)
+
+    @warn_on_args_to_kwargs()
+    def set_opacity_interpolator(self, interpolator, *, is_evaluator=False):
+        """Set the opacity interpolator.
+
+        Parameters
+        ----------
+        interpolator: callable
+            The generator function of the interpolator that would handle
+            the opacity keyframes.
+        is_evaluator: bool, optional
+            Specifies whether the `interpolator` is time-only based evaluation
+            function that does not depend on keyframes.
+
+        Examples
+        --------
+        >>> Animation.set_opacity_interpolator(step_interpolator) # doctest: +SKIP
+
+        """
+        self.set_interpolator("opacity", interpolator, is_evaluator=is_evaluator)
+
+    def get_value(self, attrib, timestamp):
+        """Return the value of an attribute at any given timestamp.
+
+        Parameters
+        ----------
+        attrib: str
+            The attribute name.
+        timestamp: float
+            The timestamp to interpolate at.
+
+        """
+        value = (
+            self._data.get(attrib, {}).get("interpolator", {}).get("func")(timestamp)
+        )
+        return value
+
+    def get_current_value(self, attrib):
+        """Return the value of an attribute at current time.
+
+        Parameters
+        ----------
+        attrib: str
+            The attribute name.
+
+        """
+        return (
+            self._data.get(attrib)
+            .get("interpolator")
+            .get("func")(self._timeline.current_timestamp)
+        )
+
+    def set_position(self, timestamp, position, **kwargs):
+        """Set a position keyframe at a specific timestamp.
+
+        Parameters
+        ----------
+        timestamp: float
+            Timestamp of the keyframe
+        position: ndarray, shape (1, 3)
+            Position value
+
+        Other Parameters
+        ----------------
+        in_cp: float
+            The control point in case of using `cubic Bézier interpolator` when
+            time exceeds this timestamp.
+        out_cp: float
+            The control point in case of using `cubic Bézier interpolator` when
+            time precedes this timestamp.
+        in_tangent: ndarray, shape (1, M), optional
+            The in tangent at that position for the cubic spline curve.
+        out_tangent: ndarray, shape (1, M), optional
+            The out tangent at that position for the cubic spline curve.
+
+        Notes
+        -----
+        `in_cp` and `out_cp` only needed when using the cubic bezier
+        interpolation method.
+
+        """
+        self.set_keyframe("position", timestamp, position, **kwargs)
+
+    def set_position_keyframes(self, keyframes):
+        """Set a dict of position keyframes at once.
+        Should be in the following form:
+        {timestamp_1: position_1, timestamp_2: position_2}
+
+        Parameters
+        ----------
+        keyframes: dict
+            A dict with timestamps as keys and positions as values.
+
+        Examples
+        --------
+        >>> pos_keyframes = {1, (0, 0, 0), 3, (50, 6, 6)}
+        >>> Animation.set_position_keyframes(pos_keyframes) # doctest: +SKIP
+
+        """
+        self.set_keyframes("position", keyframes)
+
+    def set_rotation(self, timestamp, rotation, **kwargs):
+        """Set a rotation keyframe at a specific timestamp.
+
+        Parameters
+        ----------
+        timestamp: float
+            Timestamp of the keyframe
+        rotation: ndarray, shape(1, 3) or shape(1, 4)
+            Rotation data in euler degrees with shape(1, 3) or in quaternions
+            with shape(1, 4).
+
+        Notes
+        -----
+        Euler rotations are executed by rotating first around Z then around X,
+        and finally around Y.
+
+        """
+        no_components = len(np.array(rotation).flatten())
+        if no_components == 4:
+            self.set_keyframe("rotation", timestamp, rotation, **kwargs)
+        elif no_components == 3:
+            # user is expected to set rotation order by default as setting
+            # orientation of a `vtkActor` ordered as z->x->y.
+            rotation = np.asarray(rotation, dtype=float)
+            rotation = transform.Rotation.from_euler(
+                "zxy", rotation[[2, 0, 1]], degrees=True
+            ).as_quat()
+            self.set_keyframe("rotation", timestamp, rotation, **kwargs)
+        else:
+            warn(
+                f"Keyframe with {no_components} components is not a "
+                f"valid rotation data. Skipped!",
+                stacklevel=2,
+            )
+
+    def set_rotation_as_vector(self, timestamp, vector, **kwargs):
+        """Set a rotation keyframe at a specific timestamp.
+
+        Parameters
+        ----------
+        timestamp: float
+            Timestamp of the keyframe
+        vector: ndarray, shape(1, 3)
+            Directional vector that describes the rotation.
+
+        """
+        quat = transform.Rotation.from_rotvec(vector).as_quat()
+        self.set_keyframe("rotation", timestamp, quat, **kwargs)
+
+    def set_scale(self, timestamp, scalar, **kwargs):
+        """Set a scale keyframe at a specific timestamp.
+
+        Parameters
+        ----------
+        timestamp: float
+            Timestamp of the keyframe
+        scalar: ndarray, shape(1, 3)
+            Scale keyframe value associated with the timestamp.
+
+        """
+        self.set_keyframe("scale", timestamp, scalar, **kwargs)
+
+    def set_scale_keyframes(self, keyframes):
+        """Set a dict of scale keyframes at once.
+        Should be in the following form:
+        {timestamp_1: scale_1, timestamp_2: scale_2}
+
+        Parameters
+        ----------
+        keyframes: dict
+            A dict with timestamps as keys and scales as values.
+
+        Examples
+        --------
+        >>> scale_keyframes = {1, (1, 1, 1), 3, (2, 2, 3)}
+        >>> Animation.set_scale_keyframes(scale_keyframes) # doctest: +SKIP
+
+        """
+        self.set_keyframes("scale", keyframes)
+
+    def set_color(self, timestamp, color, **kwargs):
+        """Set color keyframe at a specific timestamp.
+
+        Parameters
+        ----------
+        timestamp: float
+            Timestamp of the keyframe
+        color: ndarray, shape(1, 3)
+            Color keyframe value associated with the timestamp.
+
+        """
+        self.set_keyframe("color", timestamp, color, **kwargs)
+
+    def set_color_keyframes(self, keyframes):
+        """Set a dict of color keyframes at once.
+        Should be in the following form:
+        {timestamp_1: color_1, timestamp_2: color_2}
+
+        Parameters
+        ----------
+        keyframes: dict
+            A dict with timestamps as keys and color as values.
+
+        Examples
+        --------
+        >>> import numpy as np
+        >>> color_keyframes = {1, (1, 0, 1), 3, (0, 0, 1)}
+        >>> Animation.set_color_keyframes(color_keyframes) # doctest: +SKIP
+
+        """
+        self.set_keyframes("color", keyframes)
+
+    def set_opacity(self, timestamp, opacity, **kwargs):
+        """Set opacity keyframe at a specific timestamp.
+
+        Parameters
+        ----------
+        timestamp: float
+            Timestamp of the keyframe
+        opacity: ndarray, shape(1, 3)
+            Opacity keyframe value associated with the timestamp.
+
+        """
+        self.set_keyframe("opacity", timestamp, opacity, **kwargs)
+
+    def set_opacity_keyframes(self, keyframes):
+        """Set a dict of opacity keyframes at once.
+        Should be in the following form:
+        {timestamp_1: opacity_1, timestamp_2: opacity_2}
+
+        Parameters
+        ----------
+        keyframes: dict(float: ndarray, shape(1, 1) or float or int)
+            A dict with timestamps as keys and opacities as values.
+
+        Notes
+        -----
+        Opacity values should be between 0 and 1.
+
+        Examples
+        --------
+        >>> opacity = {1, (1, 1, 1), 3, (2, 2, 3)}
+        >>> Animation.set_scale_keyframes(opacity) # doctest: +SKIP
+
+        """
+        self.set_keyframes("opacity", keyframes)
+
+    def get_position(self, t):
+        """Return the interpolated position.
+
+        Parameters
+        ----------
+        t: float
+            The time to interpolate position at.
+
+        Returns
+        -------
+        ndarray(1, 3):
+            The interpolated position.
+
+        """
+        return self.get_value("position", t)
+
+    def get_rotation(self, t, as_quat=False):
+        """Return the interpolated rotation.
+
+        Parameters
+        ----------
+        t: float
+            the time to interpolate rotation at.
+        as_quat: bool
+            Returned rotation will be as quaternion if True.
+
+        Returns
+        -------
+        ndarray(1, 3):
+            The interpolated rotation as Euler degrees by default.
+
+        """
+        rot = self.get_value("rotation", t)
+        if len(rot) == 4:
+            if as_quat:
+                return rot
+            r = transform.Rotation.from_quat(rot)
+            degrees = r.as_euler("zxy", degrees=True)[[1, 2, 0]]
+            return degrees
+        elif not as_quat:
+            return rot
+        return transform.Rotation.from_euler(
+            "zxy", rot[[2, 0, 1]], degrees=True
+        ).as_quat()
+
+    def get_scale(self, t):
+        """Return the interpolated scale.
+
+        Parameters
+        ----------
+        t: float
+            The time to interpolate scale at.
+
+        Returns
+        -------
+        ndarray(1, 3):
+            The interpolated scale.
+
+        """
+        return self.get_value("scale", t)
+
+    def get_color(self, t):
+        """Return the interpolated color.
+
+        Parameters
+        ----------
+        t: float
+            The time to interpolate color value at.
+
+        Returns
+        -------
+        ndarray(1, 3):
+            The interpolated color.
+
+        """
+        return self.get_value("color", t)
+
+    def get_opacity(self, t):
+        """Return the opacity value.
+
+        Parameters
+        ----------
+        t: float
+            The time to interpolate opacity at.
+
+        Returns
+        -------
+        ndarray(1, 1):
+            The interpolated opacity.
+
+        """
+        return self.get_value("opacity", t)
+
+    def add(self, item):
+        """Add an item to the Animation.
+        This item can be an Actor, Animation, list of Actors, or a list of
+        Animations.
+
+        Parameters
+        ----------
+        item: Animation, vtkActor, list[Animation], or list[vtkActor]
+            Actor/s to be animated by the Animation.
+
+        """
+        if isinstance(item, list):
+            for a in item:
+                self.add(a)
+            return
+        # elif isinstance(item, Actor):
+        #     self.add_actor(item)
+        elif isinstance(item, Animation):
+            self.add_child_animation(item)
+        else:
+            raise ValueError(f"Object of type {type(item)} can't be animated")
+
+    def add_child_animation(self, animation):
+        """Add child Animation or list of Animations.
+
+        Parameters
+        ----------
+        animation: Animation or list[Animation]
+            Animation/s to be added.
+
+        """
+        if isinstance(animation, list):
+            for a in animation:
+                self.add_child_animation(a)
+            return
+        animation._parent_animation = self
+        animation.update_motion_path()
+        self._animations.append(animation)
+        self.update_duration()
+
+    @warn_on_args_to_kwargs()
+    def add_actor(self, actor, *, static=False):
+        """Add an actor or list of actors to the Animation.
+
+        Parameters
+        ----------
+        actor: vtkActor or list(vtkActor)
+            Actor/s to be animated by the Animation.
+        static: bool
+            Indicated whether the actor should be animated and controlled by
+            the animation or just a static actor that gets added to the scene
+            along with the Animation.
+
+        """
+        if isinstance(actor, list):
+            for a in actor:
+                self.add_actor(a, static=static)
+        elif static:
+            if actor not in self.static_actors:
+                self._static_actors.append(actor)
+        else:
+            if actor not in self._actors:
+                actor.vcolors = utils.colors_from_actor(actor)
+                self._actors.append(actor)
+
+    @property
+    def timeline(self):
+        """Return the Timeline handling the current animation.
+
+        Returns
+        -------
+        Timeline:
+            The Timeline handling the current animation, None, if there is no
+            associated Timeline.
+
+        """
+        return self._timeline
+
+    @timeline.setter
+    def timeline(self, timeline):
+        """Assign the Timeline responsible for handling the Animation.
+
+        Parameters
+        ----------
+        timeline: Timeline
+            The Timeline handling the current animation, None, if there is no
+            associated Timeline.
+
+        """
+        self._timeline = timeline
+        if self._animations:
+            for animation in self._animations:
+                animation.timeline = timeline
+
+    @property
+    def parent_animation(self):
+        """Return the hierarchical parent Animation for current Animation.
+
+        Returns
+        -------
+        Animation:
+            The parent Animation.
+
+        """
+        return self._parent_animation
+
+    @parent_animation.setter
+    def parent_animation(self, parent_animation):
+        """Assign a parent Animation for the current Animation.
+
+        Parameters
+        ----------
+        parent_animation: Animation
+            The parent Animation instance.
+
+        """
+        self._parent_animation = parent_animation
+
+    @property
+    def actors(self):
+        """Return a list of actors.
+
+        Returns
+        -------
+        list:
+            List of actors controlled by the Animation.
+
+        """
+        return self._actors
+
+    @property
+    def child_animations(self) -> "list[Animation]":
+        """Return a list of child Animations.
+
+        Returns
+        -------
+        list:
+            List of child Animations of this Animation.
+
+        """
+        return self._animations
+
+    def add_static_actor(self, actor):
+        """Add an actor or list of actors as static actor/s which will not be
+        controlled nor animated by the Animation. All static actors will be
+        added to the scene when the Animation is added to the scene.
+
+        Parameters
+        ----------
+        actor: vtkActor or list(vtkActor)
+            Static actor/s.
+
+        """
+        self.add_actor(actor, static=True)
+
+    @property
+    def static_actors(self):
+        """Return a list of static actors.
+
+        Returns
+        -------
+        list:
+            List of static actors.
+
+        """
+        return self._static_actors
+
+    def remove_animations(self):
+        """Remove all child Animations from the Animation"""
+        self._animations.clear()
+
+    def remove_actor(self, actor):
+        """Remove an actor from the Animation.
+
+        Parameters
+        ----------
+        actor: vtkActor
+            Actor to be removed from the Animation.
+
+        """
+        self._actors.remove(actor)
+
+    def remove_actors(self):
+        """Remove all actors from the Animation"""
+        self._actors.clear()
+
+    @property
+    def loop(self):
+        """Get loop condition of the current animation.
+
+        Returns
+        -------
+        bool
+            Whether the animation in loop mode (True) or play one mode (False).
+
+        """
+        return self._loop
+
+    @loop.setter
+    def loop(self, loop):
+        """Set the animation to loop or play once.
+
+        Parameters
+        ----------
+        loop: bool
+            The loop condition to be set. (True) to loop the animation, and
+            (False) to play only once.
+
+        """
+        self._loop = loop
+
+    def add_update_callback(self, callback, prop=None):
+        """Add a function to be called each time animation is updated
+        This function must accept only one argument which is the current value
+        of the named property.
+
+
+        Parameters
+        ----------
+        callback: callable
+            The function to be called whenever the animation is updated.
+        prop: str, optional, default: None
+            The name of the property.
+
+        Notes
+        -----
+        If no attribute name was provided, current time of the animation will
+        be provided instead of current value for the callback.
+
+        """
+        if prop is None:
+            self._general_callbacks.append(callback)
+            return
+        attrib = self._get_attribute_data(prop)
+        attrib.get("callbacks", []).append(callback)
+
+    @warn_on_args_to_kwargs()
+    def update_animation(self, *, time=None):
+        """Update the animation.
+
+        Update the animation at a certain time. This will make sure all
+        attributes are calculated and set to the actors at that given time.
+
+        Parameters
+        ----------
+        time: float or int, optional, default: None
+            The time to update animation at. If None, the animation will play
+            without adding it to a Timeline.
+
+        """
+        has_handler = True
+        if time is None:
+            time = perf_counter() - self._start_time
+            has_handler = False
+
+        # handling in/out of scene events
+        in_scene = self.is_inside_scene_at(time)
+        self._handle_scene_event(time)
+
+        if self.duration:
+            if self._loop and time > self.duration:
+                time = time % self.duration
+            elif time > self.duration:
+                time = self.duration
+        if isinstance(self._parent_animation, Animation):
+            self._transform.DeepCopy(self._parent_animation._transform)
+        else:
+            self._transform.Identity()
+
+        self._current_timestamp = time
+
+        # actors properties
+        if in_scene:
+            if self.is_interpolatable("position"):
+                position = self.get_position(time)
+                self._transform.Translate(*position)
+
+            if self.is_interpolatable("opacity"):
+                opacity = self.get_opacity(time)
+                [act.GetProperty().SetOpacity(opacity) for act in self.actors]
+
+            if self.is_interpolatable("rotation"):
+                x, y, z = self.get_rotation(time)
+                # Rotate in the same order as VTK defaults.
+                self._transform.RotateZ(z)
+                self._transform.RotateX(x)
+                self._transform.RotateY(y)
+
+            if self.is_interpolatable("scale"):
+                scale = self.get_scale(time)
+                self._transform.Scale(*scale)
+
+            if self.is_interpolatable("color"):
+                color = self.get_color(time)
+                for act in self.actors:
+                    act.vcolors[:] = color * 255
+                    utils.update_actor(act)
+
+            # update actors' transformation matrix
+            [act.SetUserTransform(self._transform) for act in self.actors]
+
+        for attrib in self._data:
+            callbacks = self._data.get(attrib, {}).get("callbacks", [])
+            if callbacks != [] and self.is_interpolatable(attrib):
+                value = self.get_value(attrib, time)
+                [cbk(value) for cbk in callbacks]
+
+        # Executing general callbacks that's not related to any attribute
+        [callback(time) for callback in self._general_callbacks]
+
+        # Also update all child Animations.
+        [animation.update_animation(time=time) for animation in self._animations]
+
+        if self._scene and not has_handler:
+            self._scene.reset_clipping_range()
+
+    def add_to_scene(self, scene):
+        """Add this Animation, its actors and sub Animations to the scene"""
+        [scene.add(actor) for actor in self._actors]
+        [scene.add(static_act) for static_act in self._static_actors]
+        [scene.add(animation) for animation in self._animations]
+
+        if self._motion_path_actor:
+            scene.add(self._motion_path_actor)
+        self._scene = scene
+        self._added_to_scene = True
+        self._start_time = perf_counter()
+        self.update_animation(time=0)
+
+    def remove_from_scene(self, scene):
+        """Remove Animation, its actors and sub Animations from the scene"""
+        [scene.rm(act) for act in self.actors]
+        [scene.rm(static_act) for static_act in self._static_actors]
+        for anim in self.child_animations:
+            anim.remove_from_scene(scene)
+        if self._motion_path_actor:
+            scene.rm(self._motion_path_actor)
+        self._added_to_scene = False
+
+
+class CameraAnimation(Animation):
+    """Camera keyframe animation class.
+
+    This is used for animating a single camera using a set of keyframes.
+
+    Attributes
+    ----------
+    camera : Camera, optional, default: None
+        Camera to be animated. If None, active camera will be animated.
+    length : float or int, default: None, optional
+        the fixed length of the animation. If set to None, the animation will
+        get its duration from the keyframes being set.
+    loop : bool, optional, default: True
+        Whether to loop the animation (True) of play once (False).
+    motion_path_res : int, default: None
+        the number of line segments used to visualizer the animation's motion
+        path (visualizing position).
+
+    """
+
+    @warn_on_args_to_kwargs()
+    def __init__(self, *, camera=None, length=None, loop=True, motion_path_res=None):
+        super(CameraAnimation, self).__init__(
+            length=length, loop=loop, motion_path_res=motion_path_res
+        )
+        self._camera = camera
+
+    # @property
+    # def camera(self) -> Camera:
+    #     """Return the camera assigned to this animation.
+
+    #     Returns
+    #     -------
+    #     Camera:
+    #         The camera that is being animated by this CameraAnimation.
+
+    #     """
+    #     return self._camera
+
+    # @camera.setter
+    # def camera(self, camera: Camera):
+    #     """Set a camera to be animated.
+
+    #     Parameters
+    #     ----------
+    #     camera: Camera
+    #         The camera to be animated
+
+    #     """
+    #     self._camera = camera
+
+    def set_focal(self, timestamp, position, **kwargs):
+        """Set camera's focal position keyframe.
+
+        Parameters
+        ----------
+        timestamp: float
+            The time to interpolate opacity at.
+        position: ndarray, shape(1, 3)
+            The camera position
+
+        """
+        self.set_keyframe("focal", timestamp, position, **kwargs)
+
+    def set_view_up(self, timestamp, direction, **kwargs):
+        """Set the camera view-up direction keyframe.
+
+        Parameters
+        ----------
+        timestamp: float
+            The time to interpolate at.
+        direction: ndarray, shape(1, 3)
+            The camera view-up direction
+
+        """
+        self.set_keyframe("view_up", timestamp, direction, **kwargs)
+
+    def set_focal_keyframes(self, keyframes):
+        """Set multiple camera focal position keyframes at once.
+        Should be in the following form:
+        {timestamp_1: focal_1, timestamp_2: focal_1, ...}
+
+        Parameters
+        ----------
+        keyframes: dict
+            A dict with timestamps as keys and camera focal positions as
+            values.
+
+        Examples
+        --------
+        >>> focal_pos = {0, (1, 1, 1), 3, (20, 0, 0)}
+        >>> CameraAnimation.set_focal_keyframes(focal_pos) # doctest: +SKIP
+
+        """
+        self.set_keyframes("focal", keyframes)
+
+    def set_view_up_keyframes(self, keyframes):
+        """Set multiple camera view up direction keyframes.
+                Should be in the following form:
+                {timestamp_1: view_up_1, timestamp_2: view_up_2, ...}
+
+                Parameters
+                ----------
+                keyframes: dict
+                    A dict with timestamps as keys and camera view up vectors as
+                    values.
+
+                Examples
+                --------
+                >>> view_ups = {
+        0, np.array([1, 0, 0]), 3, np.array([0, 1, 0])} # doctest: +SKIP
+                >>> CameraAnimation.set_view_up_keyframes(view_ups) # doctest: +SKIP
+
+        """
+        self.set_keyframes("view_up", keyframes)
+
+    def get_focal(self, t):
+        """Return the interpolated camera's focal position.
+
+        Parameters
+        ----------
+        t: float
+            The time to interpolate at.
+
+        Returns
+        -------
+        ndarray(1, 3):
+            The interpolated camera's focal position.
+
+        Notes
+        -----
+        The returned focal position does not necessarily reflect the current
+        camera's focal position, but the expected one.
+
+        """
+        return self.get_value("focal", t)
+
+    def get_view_up(self, t):
+        """Return the interpolated camera's view-up directional vector.
+
+        Parameters
+        ----------
+        t: float
+            The time to interpolate at.
+
+        Returns
+        -------
+        ndarray(1, 3):
+            The interpolated camera view-up directional vector.
+
+        Notes
+        -----
+        The returned focal position does not necessarily reflect the actual
+        camera view up directional vector, but the expected one.
+
+        """
+        return self.get_value("view_up", t)
+
+    @warn_on_args_to_kwargs()
+    def set_focal_interpolator(self, interpolator, *, is_evaluator=False):
+        """Set the camera focal position interpolator.
+
+        Parameters
+        ----------
+        interpolator: callable
+            The generator function of the interpolator that would handle the
+            interpolation of the camera focal position keyframes.
+        is_evaluator: bool, optional
+            Specifies whether the `interpolator` is time-only based evaluation
+            function that does not depend on keyframes.
+
+        """
+        self.set_interpolator("focal", interpolator, is_evaluator=is_evaluator)
+
+    @warn_on_args_to_kwargs()
+    def set_view_up_interpolator(self, interpolator, *, is_evaluator=False):
+        """Set the camera up-view vector animation interpolator.
+
+        Parameters
+        ----------
+        interpolator: callable
+            The generator function of the interpolator that would handle the
+            interpolation of the camera view-up keyframes.
+        is_evaluator: bool, optional
+            Specifies whether the `interpolator` is time-only based evaluation
+            function that does not depend on keyframes.
+
+        """
+        self.set_interpolator("view_up", interpolator, is_evaluator=is_evaluator)
+
+    @warn_on_args_to_kwargs()
+    def update_animation(self, *, time=None):
+        """Update the camera animation.
+
+        Parameters
+        ----------
+        time: float or int, optional, default: None
+            The time to update the camera animation at. If None, the animation
+            will play.
+
+        """
+        if self._camera is None:
+            if self._scene:
+                self._camera = self._scene.camera()
+                self.update_animation(tile=time)
+                return
+        else:
+            if self.is_interpolatable("rotation"):
+                pos = self._camera.GetPosition()
+                translation = np.identity(4)
+                translation[:3, 3] = pos
+                # camera axis is reverted
+                rot = -self.get_rotation(time, as_quat=True)
+                rot = transform.Rotation.from_quat(rot).as_matrix()
+                rot = np.array([[*rot[0], 0], [*rot[1], 0], [*rot[2], 0], [0, 0, 0, 1]])
+                rot = translation @ rot @ np.linalg.inv(translation)
+                self._camera.SetModelTransformMatrix(rot.flatten())
+
+            if self.is_interpolatable("position"):
+                cam_pos = self.get_position(time)
+                self._camera.SetPosition(cam_pos)
+
+            if self.is_interpolatable("focal"):
+                cam_foc = self.get_focal(time)
+                self._camera.SetFocalPoint(cam_foc)
+
+            if self.is_interpolatable("view_up"):
+                cam_up = self.get_view_up(time)
+                self._camera.SetViewUp(cam_up)
+            elif not self.is_interpolatable("view_up"):
+                # to preserve up-view as default after user interaction
+                self._camera.SetViewUp(0, 1, 0)
+            if self._scene:
+                self._scene.reset_clipping_range()