The ** Partition of Unity** window provides a user with

Once a control point is selected, the ** Partition of Unity**
window shows the coefficient of the selected control point. Since this is
a tensor product surface, the coefficient of a control point is the product
of two basis functions. The basis functions are displayed on the

The actual value of the coefficient depends on the current values of *u*
and *v*. Once a *u* (*resp.*, *v*) is given, all
basis functions at this *u* (*resp.*, *v*) partition the
interval [0,1] into shorter interval. The lengths of these subintervals are
the weights contributing to control points. The top two color bars give the
way of partition of unity. The following figures show the partitions of
unity at two different (*u*,*v*)'s. Please note that the basis
functions of the selected control point are the same; but as
(*u*,*v*) changes (by dragging the *uv*-indicator),
the way of partition of unity changes accordingly. As a result, the
coefficient (*i.e.*, product of the basis functions) will be different
for different (*u*,*v*).

If a surface is subdivided, one can click the domain of a subpatch to move to that surface. Then, selecting a control point of that patch will cause the partition of unity of that patch to appear. Please note that the basis function being displayed will have a smaller domain, because it is for a subpatch.