Add a useful package (from Source forge) for octave

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

diff --git a/octave_packages/nurbs-1.3.6/nrbtform.m b/octave_packages/nurbs-1.3.6/nrbtform.m
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+function nurbs = nrbtform(nurbs,tmat)
+% 
+% NRBTFORM: Apply transformation matrix to the NURBS.
+% 
+% Calling Sequence:
+% 
+%   tnurbs = nrbtform(nurbs,tmatrix);
+% 
+% INPUT:
+% 
+%   nurbs      : NURBS data structure (see nrbmak for details).
+% 
+%   tmatrix     : Transformation matrix, a matrix of size (4,4) defining
+%                 a single or multiple transformations.
+%
+% OUTPUT:
+%
+%   tnurbs     : The return transformed NURBS data structure.
+% 
+% Description:
+% 
+%   The NURBS is transform as defined a transformation matrix of size (4,4),
+%   such as a rotation, translation or change in scale. The transformation
+%   matrix can define a single transformation or multiple series of
+%   transformations. The matrix can be simple constructed by the functions
+%   vecscale, vectrans, vecrotx, vecroty, and vecrotz.
+%     
+% Examples:
+% 
+%   Rotate a square by 45 degrees about the z axis.
+%
+%   rsqr = nrbtform(nrbrect(), vecrotz(deg2rad(45)));
+%   nrbplot(rsqr, 1000);
+% 
+% See also:
+% 
+%   vecscale, vectrans, vecrotx, vecroty, vecrotz
+%
+%    Copyright (C) 2000 Mark Spink
+%    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 nargin < 2
+  error('Not enough input arguments!');
+end;
+
+if iscell(nurbs.knots)
+ if size(nurbs.knots,2) == 2
+  % NURBS is a surface
+  [dim,nu,nv] = size(nurbs.coefs);
+  nurbs.coefs = reshape(tmat*reshape(nurbs.coefs,dim,nu*nv),[dim nu nv]);
+ elseif size(nurbs.knots,2) == 3
+  % NURBS is a volume
+  [dim,nu,nv,nw] = size(nurbs.coefs);
+  nurbs.coefs = reshape(tmat*reshape(nurbs.coefs,dim,nu*nv*nw),[dim nu nv nw]);
+ end
+else
+  % NURBS is a curve
+  nurbs.coefs = tmat*nurbs.coefs;
+end
+
+end
+
+%!demo
+%! xx = vectrans([2.0 1.0])*vecroty(pi/8)*vecrotx(pi/4)*vecscale([1.0 2.0]);
+%! c0 = nrbtform(nrbcirc, xx);
+%! nrbplot(c0,50);
+%! grid on
+%! title('Construction of an ellipse by transforming a unit circle.');
+%! hold off
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