/usr/share/octave/packages/3.2/nurbs-1.3.3/nrbreverse.m is in octave-nurbs 1.3.3-1.
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 | function rnrb = nrbreverse(nrb)
%
% NRBREVERSE: Reverse the evaluation direction of a NURBS curve or surface.
%
% Calling Sequence:
%
% rnrb = nrbreverse(nrb);
%
% INPUT:
%
% nrb : NURBS data structure, see nrbmak.
%
% OUTPUT:
%
% rnrb : Reversed NURBS.
%
% Description:
%
% Utility function to reverse the evaluation direction of a NURBS
% curve or 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/>.
if nargin ~= 1
error('Incorrect number of input arguments');
end
if iscell(nrb.knots)
if size(nrb.knots,2) == 3
error('The function nrbreverse is not yet ready for volumes')
else
% reverse a NURBS surface
coefs = nrb.coefs(:,:,end:-1:1);
rnrb = nrbmak(coefs(:,end:-1:1,:), {1.0-fliplr(nrb.knots{1}),...
1.0-fliplr(nrb.knots{2})});
end
else
% reverse a NURBS curve
rnrb = nrbmak(fliplr(nrb.coefs), 1.0-fliplr(nrb.knots));
end
end
%!demo
%! pnts = [0.5 1.5 3.0 7.5 8.5;
%! 3.0 5.5 1.5 4.0 4.5;
%! 0.0 0.0 0.0 0.0 0.0];
%! crv1 = nrbmak(pnts,[0 0 0 1/2 3/4 1 1 1]);
%! crv2 = nrbreverse(crv1);
%! fprintf('Knots of the original curve\n')
%! disp(crv1.knots)
%! fprintf('Knots of the reversed curve\n')
%! disp(crv2.knots)
%! fprintf('Control points of the original curve\n')
%! disp(crv1.coefs(1:2,:))
%! fprintf('Control points of the reversed curve\n')
%! disp(crv2.coefs(1:2,:))
%! nrbplot(crv1,100)
%! hold on
%! nrbplot(crv2,100)
%! title('The curve and its reverse are the same')
%! hold off
|