octave_packages/nurbs-1.3.6/bspeval.m

   1 function p = bspeval(d,c,k,u)
   2
   3 % BSPEVAL:  Evaluate B-Spline at parametric points.
   4 %
   5 % Calling Sequence:
   6 %
   7 %   p = bspeval(d,c,k,u)
   8 %
   9 %    INPUT:
  10 %
  11 %       d - Degree of the B-Spline.
  12 %       c - Control Points, matrix of size (dim,nc).
  13 %       k - Knot sequence, row vector of size nk.
  14 %       u - Parametric evaluation points, row vector of size nu.
  15 %
  16 %    OUTPUT:
  17 %
  18 %       p - Evaluated points, matrix of size (dim,nu)
  19 %
  20 %    Copyright (C) 2000 Mark Spink, 2007 Daniel Claxton, 2010 C. de Falco
  21 %
  22 %    This program is free software: you can redistribute it and/or modify
  23 %    it under the terms of the GNU General Public License as published by
  24 %    the Free Software Foundation, either version 2 of the License, or
  25 %    (at your option) any later version.
  26
  27 %    This program is distributed in the hope that it will be useful,
  28 %    but WITHOUT ANY WARRANTY; without even the implied warranty of
  29 %    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  30 %    GNU General Public License for more details.
  31 %
  32 %    You should have received a copy of the GNU General Public License
  33 %    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  34
  35 nu = numel(u);
  36 [mc,nc] = size(c);
  37                                                 %   int bspeval(int d, double *c, int mc, int nc, double *k, int nk, double *u,int nu, double *p){
  38                                                 %   int ierr = 0;
  39                                                 %   int i, s, tmp1, row, col;
  40                                                 %   double tmp2;
  41                                                 %
  42                                                 %   // Construct the control points
  43                                                 %   double **ctrl = vec2mat(c,mc,nc);
  44                                                 %
  45                                                 %   // Contruct the evaluated points
  46 p = zeros(mc,nu);                               %   double **pnt = vec2mat(p,mc,nu);
  47                                                 %
  48                                                 %   // space for the basis functions
  49 %N = zeros(d+1,1);                               %   double *N = (double*) mxMalloc((d+1)*sizeof(double));
  50                                                 %
  51                                                 %   // for each parametric point i
  52 %for col=1:nu                                    %   for (col = 0; col < nu; col++) {
  53                                                 %     // find the span of u[col]
  54     s = findspan(nc-1, d, u(:), k);           %     s = findspan(nc-1, d, u[col], k);
  55     N = basisfun(s,u(:),d,k);                 %     basisfun(s, u[col], d, k, N);
  56                                                 %
  57     tmp1 = s - d + 1;                           %     tmp1 = s - d;
  58     %for row=1:mc                                %     for (row = 0; row < mc; row++)  {
  59         p = zeros (mc, nu);                               %       tmp2 = 0.0;
  60         for i=0:d                               %       for (i = 0; i <= d; i++)
  61            p = p + repmat (N(:,i+1)', mc, 1).*c(:,tmp1+i);  %   tmp2 += N[i] * ctrl[tmp1+i][row];
  62         end                                     %
  63         %p(row,:) = tmp2;                      %       pnt[col][row] = tmp2;
  64     %end                                         %     }
  65 %end                                             %   }
  66                                                 %
  67                                                 %   mxFree(N);
  68                                                 %   freevec2mat(pnt);
  69                                                 %   freevec2mat(ctrl);
  70                                                 %
  71                                                 %   return ierr;
  72 end                                             %   }