/usr/share/octave/packages/nurbs-1.3.7/private/nrb_srf_basisfun_der__.m is in octave-nurbs 1.3.7-1build1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 | function [Bu, Bv, N] = nrb_srf_basisfun_der__ (points, nrb);
% __NRB_SRF_BASISFUN_DER__: Undocumented internal function
%
% Copyright (C) 2009 Carlo de Falco
% This software comes with ABSOLUTELY NO WARRANTY; see the file
% COPYING for details. This is free software, and you are welcome
% to distribute it under the conditions laid out in COPYING.
m = size (nrb.coefs, 2) -1;
n = size (nrb.coefs, 3) -1;
p = nrb.order(1) -1;
q = nrb.order(2) -1;
u = points(1,:);
v = points(2,:);
npt = length(u);
U = nrb.knots{1};
V = nrb.knots{2};
w = squeeze(nrb.coefs(4,:,:));
spu = findspan (m, p, u, U);
spv = findspan (n, q, v, V);
N = nrbnumbasisfun (points, nrb);
NuIkuk = basisfun (spu, u, p, U);
NvJkvk = basisfun (spv, v, q, V);
NuIkukprime = basisfunder (spu, p, u, U, 1);
NuIkukprime = reshape (NuIkukprime(:,2,:), npt, []);
NvJkvkprime = basisfunder (spv, q, v, V, 1);
NvJkvkprime = reshape (NvJkvkprime(:,2,:), npt, []);
for k=1:npt
wIkaJkb(1:p+1, 1:q+1) = reshape (w(N(k, :)), p+1, q+1);
Num = (NuIkuk(k, :).' * NvJkvk(k, :)) .* wIkaJkb;
Num_du = (NuIkukprime(k, :).' * NvJkvk(k, :)) .* wIkaJkb;
Num_dv = (NuIkuk(k, :).' * NvJkvkprime(k, :)) .* wIkaJkb;
Denom = sum(sum(Num));
Denom_du = sum(sum(Num_du));
Denom_dv = sum(sum(Num_dv));
Bu(k, :) = reshape((Num_du/Denom - Denom_du.*Num/Denom.^2),1,[]);
Bv(k, :) = reshape((Num_dv/Denom - Denom_dv.*Num/Denom.^2),1,[]);
end
end
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