/usr/share/octave/packages/nurbs-1.3.13/nrbsquare.m is in octave-nurbs 1.3.13-4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 | function srf = nrbsquare (corner, lengthx, lengthy, varargin)
%
% NRBSQUARE: create the NURBS surface for a square.
%
% Calling Sequence:
%
% srf = nrbsquare (corner, lengthx, lengthy);
% srf = nrbsquare (corner, lengthx, lengthy, degree);
% srf = nrbsquare (corner, lengthx, lengthy, degree, nsub);
%
% INPUT:
% corner : the coordinates of the bottom left corner of the square.
% lenghtx : the length along the x direction.
% lenghty : the length along the y direction.
% degree : the degree of the NURBS surface, in each direction.
% nsub : the number of subdivision of the NURBS surface, in each direction.
%
% OUTPUT:
% srf : the NURBS surface.
%
% Copyright (C) 2016 Jacopo Corno, 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 3 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 (isempty (corner))
corner = [0 0];
end
nsub = [1 1];
degree = [1 1];
if (numel (varargin) >= 1)
if (numel (varargin{1}) == 1)
degree = [varargin{1} varargin{1}];
elseif (numel (varargin{1}) == 2)
degree = varargin{1};
else
error ('The degree vector should provide the degree in each direction (two values).');
end
if (numel (varargin) == 2)
if (numel (varargin{2}) == 1)
nsub = [varargin{2} varargin{2}];
elseif (numel (varargin{2}) == 2)
nsub = varargin{2};
else
error ('The nsub vector should provide the number of intervals in each direction (two values).');
end
end
end
srf = nrb4surf (corner, corner+[lengthx 0], corner+[0 lengthy], corner+[lengthx lengthy]);
srf = nrbdegelev (srf, degree-[1 1]);
[~,~,new_knots] = kntrefine (srf.knots, nsub-1, degree, degree-[1 1]);
srf = nrbkntins (srf, new_knots);
end
%!test
%! srf = nrbsquare ([], 1, 2, 2, 4);
%! assert (srf.order, [3 3]);
%! knt = [0 0 0 1/4 1/2 3/4 1 1 1];
%! assert (srf.knots, {knt knt})
%! x = linspace (0, 1, 100);
%! [X,Y] = ndgrid (x, x);
%! vals = nrbeval (srf, {x x});
%! assert (squeeze(vals(1,:,:)), X, 1e-15);
%! assert (squeeze(vals(2,:,:)), 2*Y, 1e-15);
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