The weightDriver node offers two modes for creating driving relationships.
Vector Angle is a cone based pose reader to avoid rotational issues due to Euler rotations. While simple rotation dependencies can be mostly solved with expressions or set driven keys more elaborate setups are bound to fail when two or more axes are involved. A vector angle reader is usually a good and inexpensive solution in these cases.
For more complex setups the RBF mode (Radial Basis Function) delivers the best way of interpolating an arbitrary number of values based on any number of poses. This way it’s possible to basically drive anything from anything. A common application for a RBF solver is the blending of corrective shapes or blend shapes in general. Especially when it comes to problematic areas like the shoulder, wrist or hip area. The RBF mode can easily blend between different corrective shapes based on the orientation of the joint.
weightDriver is under the terms of the MIT License