Abstract
A singular vertex cannot always be avoided in constructing networks of boundary curves. When three boundary curves, two tangents of which are collinear, meet at a singular vertex, then the region that is bounded by the curves makes T-shape. We give a necessary condition for interpolation of a 3-valent singular vertex with Bézier surfaces, suggest a subdivision method with three rectangular sub-patches including T-junctions for use when this condition is not met, and give examples of its use.
