Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / nurbs-1.3.6 / nrb4surf.m

diff --git a/octave_packages/nurbs-1.3.6/nrb4surf.m b/octave_packages/nurbs-1.3.6/nrb4surf.m
new file mode 100644 (file)
index 0000000..2ae2410
--- /dev/null
+++ b/octave_packages/nurbs-1.3.6/nrb4surf.m
@@ -0,0 +1,74 @@
+function srf = nrb4surf(p11,p12,p21,p22)
+% 
+% NRB4SURF: Constructs a NURBS bilinear surface.
+% 
+% Calling Sequence:
+% 
+%   srf = nrb4surf(p11,p12,p21,p22)
+% 
+% INPUT:
+% 
+%   p11                : Cartesian coordinate of the lhs bottom corner point.
+% 
+%   p12                : Cartesian coordinate of the rhs bottom corner point.
+% 
+%   p21                : Cartesian coordinate of the lhs top corner point.
+%  
+%   p22                : Cartesian coordinate of the rhs top corner point.
+%
+% OUTPUT:
+% 
+%   srf                : NURBS bilinear surface, see nrbmak. 
+% 
+% Description:
+% 
+%   Constructs a bilinear surface defined by four coordinates.
+% 
+%   The position of the corner points
+% 
+%          ^ V direction
+%          |
+%          ----------------
+%          |p21        p22|
+%          |              |
+%          |    SRF       |
+%          |              |
+%          |p11        p12|
+%          -------------------> U direction
+% 
+%
+%    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 nargin ~= 4
+  error('Four corner points must be defined'); 
+end
+
+coefs = cat (1, zeros (3,2,2), ones (1,2,2));
+coefs(1:length(p11),1,1) = p11(:);    
+coefs(1:length(p12),2,1) = p12(:);
+coefs(1:length(p21),1,2) = p21(:);
+coefs(1:length(p22),2,2) = p22(:);
+             
+knots  = {[0 0 1 1] [0 0 1 1]}; 
+srf = nrbmak(coefs, knots);
+
+end
+
+%!demo
+%! srf = nrb4surf([0.0 0.0 0.5],[1.0 0.0 -0.5],[0.0 1.0 -0.5],[1.0 1.0 0.5]);
+%! nrbplot(srf,[10,10]);
+%! title('Construction of a bilinear surface.');
+%! hold off