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[CreaPhase.git] / octave_packages / nurbs-1.3.6 / private / nrb_crv_basisfun_der__.m

diff --git a/octave_packages/nurbs-1.3.6/private/nrb_crv_basisfun_der__.m b/octave_packages/nurbs-1.3.6/private/nrb_crv_basisfun_der__.m
new file mode 100644 (file)
index 0000000..8857dc2
--- /dev/null
+++ b/octave_packages/nurbs-1.3.6/private/nrb_crv_basisfun_der__.m
@@ -0,0 +1,32 @@
+  function [Bu, nbfu] = nrb_crv_basisfun_der__ (points, nrb);
+%  __NRB_CRV_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.
+    n    = size (nrb.coefs, 2) -1;
+    p    = nrb.order -1;
+    u    = points;
+    U    = nrb.knots;
+    w    = nrb.coefs(4,:);
+    
+    spu  =  findspan (n, p, u, U);
+    nbfu =  numbasisfun (spu, u, p, U);
+    
+    N     = basisfun (spu, u, p, U);
+
+    Nprime = basisfunder (spu, p, u, U, 1);
+    Nprime = squeeze(Nprime(:,2,:));
+
+    
+    [Dpc, Dpk]  = bspderiv (p, w, U);
+    D           = bspeval  (p, w, U, u);
+    Dprime      = bspeval  (p-1, Dpc, Dpk, u);
+    
+
+    Bu1   = bsxfun (@(np, d) np/d , Nprime.', D);
+    Bu2   = bsxfun (@(n, dp)  n*dp, N.', Dprime./D.^2);
+    Bu    = w(nbfu+1) .* (Bu1 - Bu2).';
+
+  end