Approximation of conjugation of Bezier curves with preservation of smoothness order and additional restrictions

Bezier curves are a mandatory component of the geometric core of modern computer-aided design (CAD). The article proposes a mathematical approach that makes it possible to approximate the conjugation (connection) of Bezier curves of arbitrary degree, so that at the conjugation point the conditions of smoothness (continuity) are satisfied up to the order of an equal degree of the given Bezier curves. This approach helps to represent conjugate curves of a single Bezier curve with the degree equal to the degrees of the given curves. Additional restrictions can be imposed on the conjugate curves and the approximating curve in the form of a complete coincidence with one of the given curves, or the passage of the approximating curve through a given point and the equality of the derivatives to the given values at this point. To solve these problems, we introduced two difference metrics between the given curves and the approximating curve, and formulated optimization problems with constraints in the form of equalities. We applied the method of Lagrange multipliers which solves the corresponding system of linear algebraic equations. To represent Bezier curves, it is proposed to use the basic functions of B-splines, which allows you to use the software functions included in the geometric core of modern CAD systems. This greatly simplifies the derivation of all degree derivatives for curves and, without significant changes in the future, will make it possible to extend the results to conjugation problems of B-splines. The paper provides examples of approximations using various metrics and their limitations.