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ACTA AERONAUTICAET ASTRONAUTICA SINICA ›› 1981, Vol. 2 ›› Issue (3): 94-103.

• 论文 • Previous Articles    

A RAPIDLY RECURSIVE METHOD FOR THE B-SPLINES

Yuan Qisun   

  1. Beijing Institute of Aeronautics and Astronautics
  • Received:1980-08-01 Revised:1900-01-01 Online:1981-09-25 Published:1981-09-25

Abstract: A rapidly recursive method is presented for the (Normalized) B-splines of any order on the uniformly spaced kNot sequences.A parametric form of the B-splines is more suitable to matrix methods and possesses definite advantages for its application. Given n points P;(j =1, 2, …, n), the vectorvalued function for a B-spline curve of order M (degreeM- 1 )of the j-th segment is given by eq. ( 8 ). Ni[M]( t ) is the i-th B-splinebasis function of order M and [A[M]] is the basis matrix.Obviously, a directly recursive method for the basis matrix [A[M]] is of practical importance. According to the analysis of the characteristics of the B-spline basis functions, Ni[M]' ( t )can be calculated by algorithmThe continuity condition at the kNot is given by By integrating Ni[M]' in successive orders, a rapid recursion of the basismatrix[A[M]] is obtained. The relationships can be expressed as eqs. (14)-(18). In addition, the equations (21) and (22) can be used to check the numerical calculations in the process of recursion.A concrete application format of the method (see eq. (23)-(27)) including its programming (here omitted) is then presented. Several examples and the results of calculations by FORTRAN program show that this method is more intuitive, rapidly recursive and simple in computation. It is convenient for the mathematical analysis and application of B-splines. It is especially suitable to computer aided geometric design, finite element methods and others for engineers and technicians.