Testing tensor product Bézier surfaces for coincidence: A comprehensive solution

It is known that Bézier curves and surfaces may have multiple representations by different control polygons. The polygons may have different number of control points and may even be disjoint. Up to our knowledge, Pekerman et al. (2005) were the first to address the problem of testing two parametric polynomial curves for coincidence. Their approach is based on reduction of the input curves into canonical irreducible form. They claimed that their approach can be extended for testing tensor product surfaces but gave no further detail. In this paper we develop a new technique and provide a comprehensive solution to the problem of testing tensor product Bézier surfaces for coincidence. In (Vlachkova, 2017) an algorithm for testing Bézier curves was proposed based on subdivision. There a partial solution to the problem of testing tensor product Bézier surfaces was presented. Namely, the case where the irreducible surfaces are of same degree $(n,m)$, $n,m\in \mathbb{N}$, was resolved under certain additional condition. The other cases where one of the surfaces is of degree $(n,m)$ and the other is of degree either $(n,n+m)$, or $(n+m,m)$, or $(n+m,n+m)$ remained open. We have implemented our algorithm for testing tensor product Bézier surfaces for coincidence using Mathematica package. Experimental results and their analysis are presented.