This is a cube with a hole through it. The hole is controlled by a spline at the shifting center point, and at the shifting radius. The center line and radius are in turn controlled by two 2D splines on the cubes faces.
Additionally the circles that describe the sections of the void have an interval controlled by another spline. For the folks counting at home that is five points of control. That is too many. While some weird forms result, they end up being super loose, with nothing to push up against, and no way to reign in what's happening.