--- /dev/null
+function inurbs = nrbdegelev(nurbs, ntimes)
+%
+% NRBDEGELEV: Elevate the degree of the NURBS curve, surface or volume.
+%
+% Calling Sequence:
+%
+% ecrv = nrbdegelev(crv,utimes);
+% esrf = nrbdegelev(srf,[utimes,vtimes]);
+% evol = nrbdegelev(vol,[utimes,vtimes,wtimes]);
+%
+% INPUT:
+%
+% crv : NURBS curve, see nrbmak.
+%
+% srf : NURBS surface, see nrbmak.
+%
+% vol : NURBS volume, see nrbmak.
+%
+% utimes : Increase the degree along U direction utimes.
+%
+% vtimes : Increase the degree along V direction vtimes.
+%
+% wtimes : Increase the degree along W direction vtimes.
+%
+% OUTPUT:
+%
+% ecrv : new NURBS structure for a curve with degree elevated.
+%
+% esrf : new NURBS structure for a surface with degree elevated.
+%
+% evol : new NURBS structure for a volume with degree elevated.
+%
+%
+% Description:
+%
+% Degree elevates the NURBS curve or surface. This function uses the
+% B-Spline function bspdegelev, which interface to an internal 'C'
+% routine.
+%
+% Examples:
+%
+% Increase the NURBS surface twice along the V direction.
+% esrf = nrbdegelev(srf, [0, 2]);
+%
+% See also:
+%
+% bspdegelev
+%
+% Copyright (C) 2000 Mark Spink, 2010 Rafel 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 degree increment.');
+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
+ [dim,num1,num2,num3] = size(nurbs.coefs);
+
+ % Degree elevate along the w direction
+ if ntimes(3) == 0
+ coefs = nurbs.coefs;
+ knots{3} = nurbs.knots{3};
+ else
+ coefs = reshape(nurbs.coefs,4*num1*num2,num3);
+ [coefs,knots{3}] = bspdegelev(degree(3),coefs,nurbs.knots{3},ntimes(3));
+ num3 = size(coefs,2);
+ coefs = reshape(coefs,[4 num1 num2 num3]);
+ end
+
+ % Degree elevate along the v direction
+ if ntimes(2) == 0
+ knots{2} = nurbs.knots{2};
+ else
+ coefs = permute(coefs,[1 2 4 3]);
+ coefs = reshape(coefs,4*num1*num3,num2);
+ [coefs,knots{2}] = bspdegelev(degree(2),coefs,nurbs.knots{2},ntimes(2));
+ num2 = size(coefs,2);
+ coefs = reshape(coefs,[4 num1 num3 num2]);
+ coefs = permute(coefs,[1 2 4 3]);
+ end
+
+ % Degree elevate along the u direction
+ if ntimes(1) == 0
+ knots{1} = nurbs.knots{1};
+ else
+ coefs = permute(coefs,[1 3 4 2]);
+ coefs = reshape(coefs,4*num2*num3,num1);
+ [coefs,knots{1}] = bspdegelev(degree(1),coefs,nurbs.knots{1},ntimes(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
+ [dim,num1,num2] = size(nurbs.coefs);
+
+ % Degree elevate along the v direction
+ if ntimes(2) == 0
+ coefs = nurbs.coefs;
+ knots{2} = nurbs.knots{2};
+ else
+ coefs = reshape(nurbs.coefs,4*num1,num2);
+ [coefs,knots{2}] = bspdegelev(degree(2),coefs,nurbs.knots{2},ntimes(2));
+ num2 = size(coefs,2);
+ coefs = reshape(coefs,[4 num1 num2]);
+ end
+
+ % Degree elevate along the u direction
+ if ntimes(1) == 0
+ knots{1} = nurbs.knots{1};
+ else
+ coefs = permute(coefs,[1 3 2]);
+ coefs = reshape(coefs,4*num2,num1);
+ [coefs,knots{1}] = bspdegelev(degree(1),coefs,nurbs.knots{1},ntimes(1));
+ coefs = reshape(coefs,[4 num2 size(coefs,2)]);
+ coefs = permute(coefs,[1 3 2]);
+ end
+ end
+else
+
+ % NURBS represents a curve
+ if isempty(ntimes)
+ coefs = nurbs.coefs;
+ knots = nurbs.knots;
+ else
+ [coefs,knots] = bspdegelev(degree,nurbs.coefs,nurbs.knots,ntimes);
+ end
+
+end
+
+% construct new NURBS
+inurbs = nrbmak(coefs,knots);
+
+end
+
+%!demo
+%! crv = nrbtestcrv;
+%! plot(crv.coefs(1,:),crv.coefs(2,:),'bo')
+%! title('Degree elevation along test curve: curve and control polygons.');
+%! hold on;
+%! plot(crv.coefs(1,:),crv.coefs(2,:),'b--');
+%! nrbplot(crv,48);
+%!
+%! icrv = nrbdegelev(crv, 1);
+%!
+%! plot(icrv.coefs(1,:),icrv.coefs(2,:),'ro')
+%! plot(icrv.coefs(1,:),icrv.coefs(2,:),'r--');
+%!
+%! hold off;