--- /dev/null
+function inurbs = nrbkntins(nurbs,iknots)
+%
+% NRBKNTINS: Insert a single or multiple knots into a NURBS curve,
+% surface or volume.
+%
+% Calling Sequence:
+%
+% icrv = nrbkntins(crv,iuknots);
+% isrf = nrbkntins(srf,{iuknots ivknots});
+% ivol = nrbkntins(vol,{iuknots ivknots iwknots});
+%
+% INPUT:
+%
+% crv : NURBS curve, see nrbmak.
+%
+% srf : NURBS surface, see nrbmak.
+%
+% srf : NURBS volume, see nrbmak.
+%
+% iuknots : Knots to be inserted along U direction.
+%
+% ivknots : Knots to be inserted along V direction.
+%
+% iwknots : Knots to be inserted along W direction.
+%
+% OUTPUT:
+%
+% icrv : new NURBS structure for a curve with knots inserted.
+%
+% isrf : new NURBS structure for a surface with knots inserted.
+%
+% ivol : new NURBS structure for a volume with knots inserted.
+%
+% Description:
+%
+% Inserts knots into the NURBS data structure, these can be knots at
+% new positions or at the location of existing knots to increase the
+% multiplicity. Note that the knot multiplicity cannot be increased
+% beyond the order of the spline. Knots along the V direction can only
+% inserted into NURBS surfaces, not curve that are always defined along
+% the U direction. This function use the B-Spline function bspkntins,
+% which interfaces to an internal 'C' routine.
+%
+% Examples:
+%
+% Insert two knots into a curve, one at 0.3 and another
+% twice at 0.4
+%
+% icrv = nrbkntins(crv, [0.3 0.4 0.4])
+%
+% Insert into a surface two knots as (1) into the U knot
+% sequence and one knot into the V knot sequence at 0.5.
+%
+% isrf = nrbkntins(srf, {[0.3 0.4 0.4] [0.5]})
+%
+% See also:
+%
+% bspkntins
+%
+% Note:
+%
+% No knot multiplicity will be increased beyond the order of the spline.
+%
+% Copyright (C) 2000 Mark Spink, 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 nargin < 2
+ error('Input argument must include the NURBS and knots to be inserted');
+end
+
+if ~isstruct(nurbs)
+ error('NURBS representation is not structure!');
+end
+
+if ~strcmp(nurbs.form,'B-NURBS')
+ error('Not a recognised NURBS representation');
+end
+
+degree = nurbs.order-1;
+
+if iscell(nurbs.knots)
+ if size(nurbs.knots,2)==3
+ % NURBS represents a volume
+ num1 = nurbs.number(1);
+ num2 = nurbs.number(2);
+ num3 = nurbs.number(3);
+
+ % Insert knots along the w direction
+ if isempty(iknots{3})
+ coefs = nurbs.coefs;
+ knots{3} = nurbs.knots{3};
+ else
+ coefs = reshape(nurbs.coefs,4*num1*num2,num3);
+ [coefs,knots{3}] = bspkntins(degree(3),coefs,nurbs.knots{3},iknots{3});
+ num3 = size(coefs,2);
+ coefs = reshape(coefs,[4 num1 num2 num3]);
+ end
+
+ % Insert knots along the v direction
+ if isempty(iknots{2})
+ knots{2} = nurbs.knots{2};
+ else
+ coefs = permute(coefs,[1 2 4 3]);
+ coefs = reshape(coefs,4*num1*num3,num2);
+ [coefs,knots{2}] = bspkntins(degree(2),coefs,nurbs.knots{2},iknots{2});
+ num2 = size(coefs,2);
+ coefs = reshape(coefs,[4 num1 num3 num2]);
+ coefs = permute(coefs,[1 2 4 3]);
+ end
+
+ % Insert knots along the u direction
+ if isempty(iknots{1})
+ knots{1} = nurbs.knots{1};
+ else
+ coefs = permute(coefs,[1 3 4 2]);
+ coefs = reshape(coefs,4*num2*num3,num1);
+ [coefs,knots{1}] = bspkntins(degree(1),coefs,nurbs.knots{1},iknots{1});
+ coefs = reshape(coefs,[4 num2 num3 size(coefs,2)]);
+ coefs = permute(coefs,[1 4 2 3]);
+ end
+
+ elseif size(nurbs.knots,2)==2
+ % NURBS represents a surface
+ num1 = nurbs.number(1);
+ num2 = nurbs.number(2);
+
+ % Insert knots along the v direction
+ if isempty(iknots{2})
+ coefs = nurbs.coefs;
+ knots{2} = nurbs.knots{2};
+ else
+ coefs = reshape(nurbs.coefs,4*num1,num2);
+ [coefs,knots{2}] = bspkntins(degree(2),coefs,nurbs.knots{2},iknots{2});
+ num2 = size(coefs,2);
+ coefs = reshape(coefs,[4 num1 num2]);
+ end
+
+ % Insert knots along the u direction
+ if isempty(iknots{1})
+ knots{1} = nurbs.knots{1};
+ else
+ coefs = permute(coefs,[1 3 2]);
+ coefs = reshape(coefs,4*num2,num1);
+ [coefs,knots{1}] = bspkntins(degree(1),coefs,nurbs.knots{1},iknots{1});
+ coefs = reshape(coefs,[4 num2 size(coefs,2)]);
+ coefs = permute(coefs,[1 3 2]);
+ end
+ end
+else
+
+ % NURBS represents a curve
+ if isempty(iknots)
+ coefs = nurbs.coefs;
+ knots = nurbs.knots;
+ else
+ [coefs,knots] = bspkntins(degree,nurbs.coefs,nurbs.knots,iknots);
+ end
+
+end
+
+% construct new NURBS
+inurbs = nrbmak(coefs,knots);
+
+end
+
+%!demo
+%! crv = nrbtestcrv;
+%! plot(crv.coefs(1,:),crv.coefs(2,:),'bo')
+%! title('Knot insertion along test curve: curve and control polygons.');
+%! hold on;
+%! plot(crv.coefs(1,:),crv.coefs(2,:),'b--');
+%!
+%! nrbplot(crv,48);
+%!
+%! icrv = nrbkntins(crv,[0.125 0.375 0.625 0.875] );
+%! plot(icrv.coefs(1,:),icrv.coefs(2,:),'ro')
+%! plot(icrv.coefs(1,:),icrv.coefs(2,:),'r--');
+%! hold off
\ No newline at end of file
git://git.creatis.insa-lyon.fr / CreaPhase.git / blobdiff