Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / nurbs-1.3.6 / curvederiveval.m

diff --git a/octave_packages/nurbs-1.3.6/curvederiveval.m b/octave_packages/nurbs-1.3.6/curvederiveval.m
new file mode 100644 (file)
index 0000000..6a43c09
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+++ b/octave_packages/nurbs-1.3.6/curvederiveval.m
@@ -0,0 +1,67 @@
+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 2 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);
+  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]);