This node defines a single joint in the skeletal heirarchy. It may have any number of SkeletalJoint children that define joints further down in the heirarchy. Each joint is a point in space that may translate or rotate, effecting children joints. It is not possible to scale a point.

Motion of each joint changes the position of mesh verticies (see JointAnimation). This is controlled by the fields vertexWeights and verticies. The verticies field lists the verticies from the mesh (in JointAnimation) that this joint can change. The fraction of change of this joint applied to that vertex is specified in vertexWeights. The length of these two fields should be the same. If there are more elements in the verticies array than vertexWeights array, the vertexWeights array is padded with 0.0 to make the arrays the same length. If there are more vertexWeights than verticies, the vertexWeights array is truncated to the number of elements in the verticies array.

The sum of all weights from all SkeletalJoint nodes from a single mesh for a single vertex should total to 1.0. The results are undefined if that is not the case.

Non-spec notes:

1. Because of the large number of calculations necessary to animate a reasonably detailed model, these calculations are typically performed in the GPU with vertex shaders. There is an article that describes the process.
2. Maya allows a "bare" (or single) joint. Blender requires at least two. The first joint is typically called "root" or "root joint". This definition of SkeletalJoint allows supports either Maya's or Blender's structure.