circle3dOrigin

CIRCLE3DORIGIN Return the first point of a 3D circle.

   P = circle3dOrigin([XC YC ZC R THETA PHI])
   P = circle3dOrigin([XC YC ZC R THETA PHI PSI])
   Returns the origin point of the circle, i.e. the first point used for
   drawing circle.

   See also
   circles3d, points3d, circle3dPosition

0001 function ori = circle3dOrigin(varargin)
0002 %CIRCLE3DORIGIN Return the first point of a 3D circle.
0003 %
0004 %   P = circle3dOrigin([XC YC ZC R THETA PHI])
0005 %   P = circle3dOrigin([XC YC ZC R THETA PHI PSI])
0006 %   Returns the origin point of the circle, i.e. the first point used for
0007 %   drawing circle.
0008 %
0009 %   See also
0010 %   circles3d, points3d, circle3dPosition
0011 
0012 % ------
0013 % Author: David Legland
0014 % E-mail: david.legland@inrae.fr
0015 % Created: 2005-02-21
0016 % Copyright 2005-2024 INRA - TPV URPOI - BIA IMASTE
0017 
0018 % get center and radius
0019 circle = varargin{1};
0020 xc = circle(:,1);
0021 yc = circle(:,2);
0022 zc = circle(:,3);
0023 r  = circle(:,4);
0024 
0025 % get angle of normal
0026 theta   = circle(:,5);
0027 phi     = circle(:,6);
0028 
0029 % get roll
0030 if size(circle, 2)==7
0031     psi = circle(:,7);
0032 else
0033     psi = zeros(size(circle, 1), 1);
0034 end
0035 
0036 % create origin point
0037 pt0 = [r 0 0];
0038 
0039 % compute transformation from local basis to world basis
0040 trans   = localToGlobal3d(xc, yc, zc, theta, phi, psi);
0041 
0042 % transform the point
0043 ori = transformPoint3d(pt0, trans);