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view extra/nurbs/inst/curvederiveval.m @ 12662:2a027badd794 octave-forge
Added a message id in the warning
author | rafavzqz |
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date | Tue, 07 Jul 2015 13:52:48 +0000 |
parents | 37d08939bb7b |
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function ck = curvederiveval (n, p, U, P, u, d) % % CURVEDERIVEVAL: Compute the derivatives of a B-spline curve. % % usage: ck = curvederiveval (n, p, U, P, u, d) % % INPUT: % % n+1 = number of control points % p = spline order % U = knots % P = control points % u = evaluation point % d = derivative order % % OUTPUT: % % ck (k+1) = curve differentiated k times % % Adaptation of algorithm A3.4 from the NURBS book, pg99 % % Copyright (C) 2009 Carlo de Falco % Copyright (C) 2010 Rafael Vazquez % % This program is free software: you can redistribute it and/or modify % it under the terms of the GNU General Public License as published by % the Free Software Foundation, either version 3 of the License, or % (at your option) any later version. % This program is distributed in the hope that it will be useful, % but WITHOUT ANY WARRANTY; without even the implied warranty of % MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the % GNU General Public License for more details. % % You should have received a copy of the GNU General Public License % along with this program. If not, see <http://www.gnu.org/licenses/>. ck = zeros (d+1, 1); du = min (d, p); span = findspan (n, p, u, U); N = zeros (p+1, p+1); for ip=0:p N(1:ip+1,ip+1) = basisfun (span, u, ip, U)'; end pk = curvederivcpts (n, p, U, P, du, span-p, span); for k = 0:du for j = 0:p-k ck(k+1) = ck(k+1) + N(j+1,p-k+1)*pk(k+1,j+1); end end end %!test %! k = [0 0 0 1 1 1]; %! coefs(:,1) = [0;0;0;1]; %! coefs(:,2) = [1;0;1;1]; %! coefs(:,3) = [1;1;1;1]; %! crv = nrbmak (coefs, k); %! ck = curvederiveval (crv.number-1, crv.order-1, crv.knots, squeeze (crv.coefs(1,:,:)), 0.5, 2); %! assert(ck, [0.75; 1; -2]); %! ck = curvederiveval (crv.number-1, crv.order-1, crv.knots, squeeze (crv.coefs(2,:,:)), 0.5, 2); %! assert(ck, [0.25; 1; 2]); %! ck = curvederiveval (crv.number-1, crv.order-1, crv.knots, squeeze (crv.coefs(3,:,:)), 0.5, 2); %! assert(ck, [0.75; 1; -2]);