Add a useful package (from Source forge) for octave

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

diff --git a/octave_packages/nurbs-1.3.6/nrbruled.m b/octave_packages/nurbs-1.3.6/nrbruled.m
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+function srf = nrbruled (crv1, crv2)
+
+% NRBRULED: Construct a ruled surface between two NURBS curves.
+% 
+% Calling Sequence:
+% 
+%   srf = nrbruled(crv1, crv2)
+% 
+% INPUT:
+% 
+%   crv1       : First NURBS curve, see nrbmak.
+% 
+%   crv2       : Second NURBS curve, see nrbmak.
+%
+% OUTPUT:
+% 
+%   srf                : Ruled NURBS surface.
+% 
+% Description:
+% 
+%   Constructs a ruled surface between two NURBS curves. The ruled surface is
+%   ruled along the V direction.
+% 
+% Examples:
+% 
+%   Construct a ruled surface between a semicircle and a straight line.
+% 
+%   cir = nrbcirc(1,[0 0 0],0,pi);
+%   line = nrbline([-1 0.5 1],[1 0.5 1]);
+%   srf = nrbruled(cir,line);
+%   nrbplot(srf,[20 20]);
+%
+%    Copyright (C) 2000 Mark Spink
+%
+%    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 (iscell(crv1.knots) || iscell(crv2.knots))
+  error ('Both NURBS must be curves');
+end
+
+% ensure both curves have a common degree
+d = max ([crv1.order, crv2.order]);
+crv1 = nrbdegelev (crv1, d - crv1.order);
+crv2 = nrbdegelev (crv2, d - crv2.order);
+
+% merge the knot vectors, to obtain a common knot vector
+k1 = crv1.knots;
+k2 = crv2.knots;
+ku = unique ([k1 k2]);
+n = length (ku);
+ka = [];
+kb = [];
+for i = 1:n
+  i1 = length (find (k1 == ku(i)));
+  i2 = length (find (k2 == ku(i)));
+  m = max (i1, i2);
+  ka = [ka ku(i)*ones(1,m-i1)];
+  kb = [kb ku(i)*ones(1,m-i2)];
+end
+crv1 = nrbkntins (crv1, ka);
+crv2 = nrbkntins (crv2, kb);
+
+coefs(:,:,1) = crv1.coefs;
+coefs(:,:,2) = crv2.coefs;
+srf = nrbmak (coefs, {crv1.knots, [0 0 1 1]});
+
+end
+
+%!demo
+%! pnts = [0.5 1.5 4.5 3.0 7.5 6.0 8.5;
+%!         3.0 5.5 5.5 1.5 1.5 4.0 4.5;
+%!         0.0 0.0 0.0 0.0 0.0 0.0 0.0];
+%! crv1 = nrbmak (pnts,[0 0 0 1/4 1/2 3/4 3/4 1 1 1]);
+%! crv2 = nrbtform (nrbcirc (4,[4.5;0],pi,0.0),vectrans([0.0 4.0 -4.0]));
+%! srf = nrbruled (crv1,crv2);
+%! nrbplot (srf,[40 20]);
+%! title ('Ruled surface construction from two NURBS curves.');
+%! hold off
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