The Spatial Constraint is similar to the previous two constraint tools in that the parts of the SubD to which it is assigned are influenced by proximity. With this tool, however, you may only use orthogonal planes for the constraint entities. Because it works spatially, it is particularly useful for objects that will have variations that are not necessarily uniformly scaled. With multiple planes, you can easily achieve parametric adjustments in volume. In fact, it is even possible to control the X, Y, and Z coordinates of the points by different sets of planes.
The images below show setting up a default 8 size flip flop and modifying the SubD to a size 12 by changing the planes with spatial constraint set on all vertices.
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