--- /dev/null
+function srf = nrbtestsrf
+% NRBTESTSRF: Constructs a simple test surface.
+%
+% 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/>.
+
+% allocate multi-dimensional array of control points
+pnts = zeros(3,5,5);
+
+% define a grid of control points
+% in this case a regular grid of u,v points
+% pnts(3,u,v)
+%
+
+pnts(:,:,1) = [ 0.0 3.0 5.0 8.0 10.0; % w*x
+ 0.0 0.0 0.0 0.0 0.0; % w*y
+ 2.0 2.0 7.0 7.0 8.0]; % w*z
+
+pnts(:,:,2) = [ 0.0 3.0 5.0 8.0 10.0;
+ 3.0 3.0 3.0 3.0 3.0;
+ 0.0 0.0 5.0 5.0 7.0];
+
+pnts(:,:,3) = [ 0.0 3.0 5.0 8.0 10.0;
+ 5.0 5.0 5.0 5.0 5.0;
+ 0.0 0.0 5.0 5.0 7.0];
+
+pnts(:,:,4) = [ 0.0 3.0 5.0 8.0 10.0;
+ 8.0 8.0 8.0 8.0 8.0;
+ 5.0 5.0 8.0 8.0 10.0];
+
+pnts(:,:,5) = [ 0.0 3.0 5.0 8.0 10.0;
+ 10.0 10.0 10.0 10.0 10.0;
+ 5.0 5.0 8.0 8.0 10.0];
+
+% knots
+knots{1} = [0 0 0 1/3 2/3 1 1 1]; % knots along u
+knots{2} = [0 0 0 1/3 2/3 1 1 1]; % knots along v
+
+% make and draw nurbs surface
+srf = nrbmak(pnts,knots);
+
+end
+
+%!demo
+%! srf = nrbtestsrf;
+%! nrbplot(srf,[20 30])
+%! title('Test surface')
+%! hold off
+