Add a basic animation system

[waynemwashuma]

Objective

Introduces a foundational implementation for animation playback. It adds support for defining animation clips, associating them with entities, and driving arbitrary targets which are updated over time through animation clips.

Technical Detail

The following are new concepts introduced:

• AnimationClip: Represents a collection of time-based animation data.Acts as the container for one or more AnimationTracks.
• ​AnimationTrack: Defines a timeline of keyframes for a single effector type.Supports multiple effector categories:
• AnimationEffector: Defines the way that an AnimationTrack affects an entity, component or resource.
• AnimationPlayer : Component responsible for playback control of a multiple animation clips.
• AnimationTarget: Component which marks an entity to be animated by an AnimationPlayer.

The following animation effectors have been implemented to test the animation system:

• Position2DAnimationEffector: Affects the position of a 2d entity.
• Orientation2DAnimationEffector: Affects the orientation of a 2d entity.
• Scale2DAnimationEffector: Affects the scale of a 2d entity.
• Position3DAnimationEffector: Affects the position of a 3d entity.
• Orientation3DAnimationEffector: Affects the orientation of a 3d entity.
• Scale3DAnimationEffector: Affects the scale of a 3d entity.

Future work:

• Advanced easing functions e.g cubic, descrete.
• Animation blending through a mixer(and maybe an animation graph)
• Animation weights.
• Animation masking.
• Animation events.

Solution

N/A

Showcase

See the demo added.

Migration guide

N/A

Checklist

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.