Description

Imagine taking the network of patch boundaries, and by stretching it a bit, flattening it out onto a plane. Next, look for a pair of intersections that, if cut in half, would split the network into two separate pieces. If such a pair of intersections exist (called a split pair), the network is not triconnected (at least 3 intersections have to be cut in half to split a triconnected network in two). In a network that is not triconnected, there is more than one way to identify a set of segment-intersection loops which form the boundaries of patches. There is a good chance that one of these configurations produces patches with more than 4 sides, even though the shape of the curves do not suggest this. An example of this is shown in Figure 3:128 below.

Figure 3:128. The result of a boundary network that is not triconnected. Region A can be separated from region B by splitting the network at the two points shown.