Some negative results in N-sided patches
To ease surface definition in situations of complex topology, patches with other than four sides and with guaranted continuity of at least slope with adjacent patches are needed. There are known techniques in the literature for three- and five-sided patches of reasonably economy, and known transfinite methods for many sides. Some of the conditions that a six-sided patch must satisfy and how certain simpler approaches are not effective are shown.
Sabin, M.↗