Add a useful package (from Source forge) for octave

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

diff --git a/octave_packages/nurbs-1.3.6/nrbdegelev.m b/octave_packages/nurbs-1.3.6/nrbdegelev.m
new file mode 100644 (file)
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+++ b/octave_packages/nurbs-1.3.6/nrbdegelev.m
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+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;