1. Introduction
Surface blending is an important topic in geometric modelling. Simple and classical quadrics are also popularly used in engineering applications. The blending problem of quadrics thus deserves further research. For 2-way blending of circular quadrics, many methods were proposed. In those methods, many different blending surfaces are adopted, including parametric surfaces, implicit surfaces and subdivision surfaces etc. For -way blending of circular quadrics, one may also find a few existing methods([1]–[6]). Some subdivision methods designed for general parametric base surfaces can be used to blend quadrics. But we know that a suitable initial frame of subdivision surface is often difficult to construct for blending problem. Additionally, subdivision methods can only obtain an approximate surface result. Wu and Zhou([3]) blended several quadrics with an algebraic surface. They transformed blending into solving a linear system. But such an algebraic surface exists only when all blending boundaries lie on a certain quadric. Chen et al.([4]) proposed to blend several quadrics with piecewise algebraic surfaces. A space partition is needed at first. But they haven't presented an automatic and effective approach for such a space partition.