function [dc,dk] = bspderiv(d,c,k)
% BSPDERIV B-Spline derivative
% -------------------------------------------------------------------------
% ADAPTATION of BSPDERIV from C Routine
% -------------------------------------------------------------------------
%
% MATLAB SYNTAX:
%
% [dc,dk] = bspderiv(d,c,k)
%
% INPUT:
%
% d - degree of the B-Spline
% c - control points double matrix(mc,nc)
% k - knot sequence double vector(nk)
%
% OUTPUT:
%
% dc - control points of the derivative double matrix(mc,nc)
% dk - knot sequence of the derivative double vector(nk)
%
% Modified version of Algorithm A3.3 from 'The NURBS BOOK' pg98.
[mc,nc] = size(c);
nk = numel(k);
%
% int bspderiv(int d, double *c, int mc, int nc, double *k, int nk, double *dc,
% double *dk)
% {
% int ierr = 0;
% int i, j, tmp;
%
% // control points
% double **ctrl = vec2mat(c,mc,nc);
%
% // control points of the derivative
dc = zeros(mc,nc-1); % double **dctrl = vec2mat(dc,mc,nc-1);
%
for i=0:nc-2 % for (i = 0; i < nc-1; i++) {
tmp = d / (k(i+d+2) - k(i+2)); % tmp = d / (k[i+d+1] - k[i+1]);
for j=0:mc-1 % for (j = 0; j < mc; j++) {
dc(j+1,i+1) = tmp*(c(j+1,i+2) - c(j+1,i+1)); % dctrl[i][j] = tmp * (ctrl[i+1][j] - ctrl[i][j]);
end % }
end % }
%
dk = zeros(1,nk-2); % j = 0;
for i=1:nk-2 % for (i = 1; i < nk-1; i++)
dk(i) = k(i+1); % dk[j++] = k[i];
end %
% freevec2mat(dctrl);
% freevec2mat(ctrl);
%
% return ierr;
% }