X-Git-Url: https://git.creatis.insa-lyon.fr/pubgit/?p=CreaPhase.git;a=blobdiff_plain;f=octave_packages%2Fnurbs-1.3.6%2Ffindspan.m;fp=octave_packages%2Fnurbs-1.3.6%2Ffindspan.m;h=e0db51ed611dd7e82d2aa58299f12dbb573bf3c3;hp=0000000000000000000000000000000000000000;hb=c880e8788dfc484bf23ce13fa2787f2c6bca4863;hpb=1705066eceaaea976f010f669ce8e972f3734b05

diff --git a/octave_packages/nurbs-1.3.6/findspan.m b/octave_packages/nurbs-1.3.6/findspan.m
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+function s = findspan(n,p,u,U)                
+% FINDSPAN  Find the span of a B-Spline knot vector at a parametric point
+%
+% Calling Sequence:
+% 
+%   s = findspan(n,p,u,U)
+% 
+%  INPUT:
+% 
+%    n - number of control points - 1
+%    p - spline degree
+%    u - parametric point
+%    U - knot sequence
+% 
+%  OUTPUT:
+% 
+%    s - knot span index
+%
+%  Modification of Algorithm A2.1 from 'The NURBS BOOK' pg68
+%
+%    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/>.                                                
+
+if (max(u(:))>U(end) || min(u(:))<U(1))
+  error('Some value is outside the knot span')
+end
+
+s = zeros(size(u));
+for j = 1:numel(u)
+  if (u(j)==U(n+2)), s(j)=n; continue, end
+  s(j) = find(u(j) >= U,1,'last')-1;
+end
+
+end
+
+%!test
+%!  n = 3; 
+%!  U = [0 0 0 1/2 1 1 1]; 
+%!  p = 2; 
+%!  u = linspace(0, 1, 10);  
+%!  s = findspan (n, p, u, U);
+%!  assert (s, [2*ones(1, 5) 3*ones(1, 5)]);
+
+%!test
+%! p = 2; m = 7; n = m - p - 1;
+%! U = [zeros(1,p)  linspace(0,1,m+1-2*p) ones(1,p)];
+%! u = [ 0   0.11880   0.55118   0.93141   0.40068   0.35492 0.44392   0.88360   0.35414   0.92186   0.83085   1];
+%! s = [2   2   3   4   3   3   3   4   3   4   4   4];
+%! assert (findspan (n, p, u, U), s, 1e-10);