function rnrb = nrbreverse(nrb)
%
% NRBREVERSE: Reverse the evaluation direction of a NURBS curve or surface.
% 
% Calling Sequence:
% 
%   rnrb = nrbreverse(nrb);
% 
% Parameters:
% 
%   nrb		: NURBS data structure, see nrbmak.
% 
%   rnrb		: Reversed NURBS.
% 
% Description:
% 
%   Utility function to reverse the evaluation direction of a NURBS
%   curve or surface.

%  D.M. Spink
%  Copyright (c) 2000.

if nargin ~= 1
  error('Incorrect number of input arguments');
end

if iscell(nrb.knots)

  % 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})});           

else

  % reverse a NURBS curve
  rnrb = nrbmak(fliplr(nrb.coefs), 1.0-fliplr(nrb.knots));

end