Get the 3D index from a BoundaryState in WorkletPointNeighborhood
There are occasions when you need a worklet to opeate on 2D or 3D indices. Most worklets operate on 1D indices, which requires recomputing the 3D index in each worklet instance. A workaround is to use a worklet that does a 3D scheduling and pull the working index from that.
The problem was that there was no easy way to get this 3D index. To
provide this option, a feature was added to the BoundaryState class
that can be provided by WorkletPointNeighborhood.
Thus, to get a 3D index in a worklet, use the
WorkletPointNeighborhood, add Boundary as an argument to the
ExecutionSignature, and then call GetCenterIndex on the
BoundaryState object passed to the worklet operator.
Fixes #753 (closed)