/usr/share/octave/packages/nurbs-1.3.10/nrbdegelev.m is in octave-nurbs 1.3.10-1.
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 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 | function inurbs = nrbdegelev(nurbs, ntimes)
%
% NRBDEGELEV: Elevate the degree of the NURBS curve, surface or volume.
%
% Calling Sequence:
%
% ecrv = nrbdegelev(crv,utimes);
% esrf = nrbdegelev(srf,[utimes,vtimes]);
% evol = nrbdegelev(vol,[utimes,vtimes,wtimes]);
%
% INPUT:
%
% crv : NURBS curve, see nrbmak.
%
% srf : NURBS surface, see nrbmak.
%
% vol : NURBS volume, see nrbmak.
%
% utimes : Increase the degree along U direction utimes.
%
% vtimes : Increase the degree along V direction vtimes.
%
% wtimes : Increase the degree along W direction vtimes.
%
% OUTPUT:
%
% ecrv : new NURBS structure for a curve with degree elevated.
%
% esrf : new NURBS structure for a surface with degree elevated.
%
% evol : new NURBS structure for a volume with degree elevated.
%
%
% Description:
%
% Degree elevates the NURBS curve or surface. This function uses the
% B-Spline function bspdegelev, which interface to an internal 'C'
% routine.
%
% Examples:
%
% Increase the NURBS surface twice along the V direction.
% esrf = nrbdegelev(srf, [0, 2]);
%
% See also:
%
% bspdegelev
%
% Copyright (C) 2000 Mark Spink, 2010 Rafel 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 nargin < 2
error('Input argument must include the NURBS and degree increment.');
end
if ~isstruct(nurbs)
error('NURBS representation is not structure!');
end
if ~strcmp(nurbs.form,'B-NURBS')
error('Not a recognised NURBS representation');
end
degree = nurbs.order-1;
if iscell(nurbs.knots)
if size(nurbs.knots,2) == 3
% NURBS represents a volume
[dim,num1,num2,num3] = size(nurbs.coefs);
% Degree elevate along the w direction
if ntimes(3) == 0
coefs = nurbs.coefs;
knots{3} = nurbs.knots{3};
else
coefs = reshape(nurbs.coefs,4*num1*num2,num3);
[coefs,knots{3}] = bspdegelev(degree(3),coefs,nurbs.knots{3},ntimes(3));
num3 = size(coefs,2);
coefs = reshape(coefs,[4 num1 num2 num3]);
end
% Degree elevate along the v direction
if ntimes(2) == 0
knots{2} = nurbs.knots{2};
else
coefs = permute(coefs,[1 2 4 3]);
coefs = reshape(coefs,4*num1*num3,num2);
[coefs,knots{2}] = bspdegelev(degree(2),coefs,nurbs.knots{2},ntimes(2));
num2 = size(coefs,2);
coefs = reshape(coefs,[4 num1 num3 num2]);
coefs = permute(coefs,[1 2 4 3]);
end
% Degree elevate along the u direction
if ntimes(1) == 0
knots{1} = nurbs.knots{1};
else
coefs = permute(coefs,[1 3 4 2]);
coefs = reshape(coefs,4*num2*num3,num1);
[coefs,knots{1}] = bspdegelev(degree(1),coefs,nurbs.knots{1},ntimes(1));
coefs = reshape(coefs,[4 num2 num3 size(coefs,2)]);
coefs = permute(coefs,[1 4 2 3]);
end
elseif size(nurbs.knots,2) == 2
% NURBS represents a surface
[dim,num1,num2] = size(nurbs.coefs);
% Degree elevate along the v direction
if ntimes(2) == 0
coefs = nurbs.coefs;
knots{2} = nurbs.knots{2};
else
coefs = reshape(nurbs.coefs,4*num1,num2);
[coefs,knots{2}] = bspdegelev(degree(2),coefs,nurbs.knots{2},ntimes(2));
num2 = size(coefs,2);
coefs = reshape(coefs,[4 num1 num2]);
end
% Degree elevate along the u direction
if ntimes(1) == 0
knots{1} = nurbs.knots{1};
else
coefs = permute(coefs,[1 3 2]);
coefs = reshape(coefs,4*num2,num1);
[coefs,knots{1}] = bspdegelev(degree(1),coefs,nurbs.knots{1},ntimes(1));
coefs = reshape(coefs,[4 num2 size(coefs,2)]);
coefs = permute(coefs,[1 3 2]);
end
end
else
% NURBS represents a curve
if isempty(ntimes)
coefs = nurbs.coefs;
knots = nurbs.knots;
else
[coefs,knots] = bspdegelev(degree,nurbs.coefs,nurbs.knots,ntimes);
end
end
% construct new NURBS
inurbs = nrbmak(coefs,knots);
end
%!demo
%! crv = nrbtestcrv;
%! plot(crv.coefs(1,:),crv.coefs(2,:),'bo')
%! title('Degree elevation along test curve: curve and control polygons.');
%! hold on;
%! plot(crv.coefs(1,:),crv.coefs(2,:),'b--');
%! nrbplot(crv,48);
%!
%! icrv = nrbdegelev(crv, 1);
%!
%! plot(icrv.coefs(1,:),icrv.coefs(2,:),'ro')
%! plot(icrv.coefs(1,:),icrv.coefs(2,:),'r--');
%!
%! hold off;
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