The `com.jme3.animation` package contains various classes for managing animation inside a jME3 application. Currently, the majority of classes are for handling skeletal animation. The primary control class is the {@link com.jme3.animation.AnimControl}, through which animations can be played, looped, combined, transitioned, etc.

### Usage

`// Create or load a model with skeletal animation:
Spatial model = assetManager.loadModel("...");
// Retrieve the AnimControl.
AnimControl animCtrl = model.getControl(AnimControl.class);
// Create an animation channel, by default assigned to all bones.
AnimChannel animChan = animCtrl.createChannel();
// Play an animation
animChan.setAnim("MyAnim");
`

### Skeletal Animation System

jME3 uses a system of bone-weights: A vertex is assigned up to 4 bones by which it is influenced and 4 weights that describe how much the bone influences the vertex. The maximum weight value being 1.0, and the requirement that all 4 weights for a given vertex must sum to 1.0. This data is specified for each skin/mesh that is influenced by the animation control via the {link com.jme3.scene.VertexBuffer}s `BoneWeight` and `BoneIndex`. The BoneIndex buffer must be of the format `UnsignedByte`, thus placing the limit of up to 256 bones for a skeleton. The BoneWeight buffer should be of the format `Float`. Both buffers should reference 4 bones, even if the maximum number of bones any vertex is influenced is less or more than 4.
If a vertex is influenced by less than 4 bones, the indices following the last valid bone should be 0 and the weights following the last valid bone should be 0.0. The buffers are designed in such a way so as to permit hardware skinning.

The {@link com.jme3.animation.Skeleton} class describes a bone heirarchy with one or more root bones having children, thus containing all bones of the skeleton. In addition to accessing the bones in the skeleton via the tree heirarchy, it is also possible to access bones via index. The index for any given bone is arbitrary and does not depend on the bone's location in the tree hierarchy. It is this index that is specified in the BoneIndex VertexBuffer mentioned above , and is also used to apply transformations to the bones through the animations.

Every bone has a local and model space transformation. The local space transformation is relative to its parent, if it has one, otherwise it is relative to the model. The model space transformation is relative to model space. The bones additionally have a bind pose transformation, which describes the transformations for bones when no animated pose is applied to the skeleton. All bones must have a bind pose transformation before they can be animated. To set the bind pose for the skeleton, set the local (relative to parent) transformations for all the bones using the call {@link com.jme3.animation.Bone#setBindTransforms(com.jme3.math.Vector3f, com.jme3.math.Quaternion, com.jme3.math.Vector3f) }. Then call {@link com.jme3.animation.Skeleton#updateWorldVectors() } followed by {@link com.jme3.animation.Skeleton#setBindingPose() }.

Animations are stored in a HashMap object, accessed by name. An animation is simply a list of tracks, each track describes a timeline with each keyframe having a transformation. For bone animations, every track is assigned to a bone, while for morph animations, every track is assigned to a mesh.