Add a useful package (from Source forge) for octave

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

diff --git a/octave_packages/nurbs-1.3.6/surfderiveval.m b/octave_packages/nurbs-1.3.6/surfderiveval.m
new file mode 100644 (file)
index 0000000..b51e414
--- /dev/null
+++ b/octave_packages/nurbs-1.3.6/surfderiveval.m
@@ -0,0 +1,95 @@
+function skl = surfderiveval (n, p, U, m, q, V, P, u, v, d) 
+%
+% SURFDERIVEVAL: Compute the derivatives of a B-spline surface
+% 
+% usage: skl = surfderiveval (n, p, U, m, q, V, P, u, v, d) 
+%
+%  INPUT: 
+%
+%        n+1, m+1 = number of control points
+%        p, q     = spline order
+%        U, V     = knots
+%        P        = control points
+%        u,v      = evaluation points
+%        d        = derivative order
+%
+%  OUTPUT:
+%
+%        skl (k+1, l+1) =  surface differentiated k
+%                          times in the u direction and l
+%                          times in the v direction
+%
+% Adaptation of algorithm A3.8 from the NURBS book, pg115
+%
+%    Copyright (C) 2009 Carlo de Falco
+%
+%    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/>.
+
+  skl = zeros (d+1, d+1);
+  du = min (d, p);   
+  dv = min (d, q);   
+
+  uspan = findspan (n, p, u, U);
+  for ip=0:p
+      Nu(1:ip+1,ip+1) = basisfun (uspan, u, ip, U)';
+  end
+  
+  vspan = findspan (m, q, v, V);
+  for ip=0:q
+      Nv(1:ip+1,ip+1) = basisfun (vspan, v, ip, V)';
+  end
+
+  pkl = surfderivcpts (n, p, U, m, q, V, P, d, uspan-p, uspan,  ...
+                      vspan-q, vspan);
+
+  for k = 0:du
+    dd = min (d-k, dv);
+    for l = 0:dd
+      skl(k+1,l+1) =0;
+      for i=0:q-l
+       tmp = 0;
+       for j = 0:p-k
+        tmp = tmp + Nu(j+1,p-k+1) * pkl(k+1,l+1,j+1,i+1);
+       end
+       skl(k+1,l+1) = skl(k+1,l+1) + Nv(i+1,q-l+1)*tmp;
+      end
+    end
+  end
+  
+end
+
+%!shared srf
+%!test
+%! k = [0 0 0 1 1 1];
+%! c = [0 1/2 1];
+%! [coef(2,:,:), coef(1,:,:)] = meshgrid (c, c);
+%! srf = nrbmak (coef, {k, k});
+%! skl = surfderiveval (srf.number(1)-1, ...
+%!                      srf.order(1)-1, ...
+%!                      srf.knots{1}, ...
+%!                      srf.number(2)-1, ...
+%!                      srf.order(2)-1, ...
+%!                      srf.knots{2},...
+%!                      squeeze(srf.coefs(1,:,:)), .5, .5, 1) ;
+%! assert (skl, [.5 0; 1 0])
+%!test
+%! srf = nrbkntins (srf, {[], rand(1,2)});
+%! skl = surfderiveval (srf.number(1)-1,... 
+%!                      srf.order(1)-1, ...
+%!                      srf.knots{1},...
+%!                      srf.number(2)-1,... 
+%!                      srf.order(2)-1, ...
+%!                      srf.knots{2},...
+%!                      squeeze(srf.coefs(1,:,:)), .5, .5, 1) ;
+%! assert (skl, [.5 0; 1 0], 100*eps)
\ No newline at end of file