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tr2angvec

PURPOSE ^

TR2ANGVEC Convert to angle/vector form

SYNOPSIS ^

function [theta, v] = tr2angvec(t)

DESCRIPTION ^

TR2ANGVEC Convert to angle/vector form

     [THETA V] = TR2ANGVEC(M)

 Returns a vector/angle representation of the pose corresponding to M, either a rotation
 matrix or the rotation part of a homogeneous transform.
 This is a rotation of THETA about the vector V.

 See also: ANGVEC2R, ANGVEC2TR

CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:

SOURCE CODE ^

0001 %TR2ANGVEC Convert to angle/vector form
0002 %
0003 %     [THETA V] = TR2ANGVEC(M)
0004 %
0005 % Returns a vector/angle representation of the pose corresponding to M, either a rotation
0006 % matrix or the rotation part of a homogeneous transform.
0007 % This is a rotation of THETA about the vector V.
0008 %
0009 % See also: ANGVEC2R, ANGVEC2TR
0010 
0011 % Copyright (C) 1993-2008, by Peter I. Corke
0012 %
0013 % This file is part of The Robotics Toolbox for Matlab (RTB).
0014 %
0015 % RTB is free software: you can redistribute it and/or modify
0016 % it under the terms of the GNU Lesser General Public License as published by
0017 % the Free Software Foundation, either version 3 of the License, or
0018 % (at your option) any later version.
0019 %
0020 % RTB is distributed in the hope that it will be useful,
0021 % but WITHOUT ANY WARRANTY; without even the implied warranty of
0022 % MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
0023 % GNU Lesser General Public License for more details.
0024 %
0025 % You should have received a copy of the GNU Leser General Public License
0026 % along with RTB.  If not, see <http://www.gnu.org/licenses/>.
0027 
0028 function [theta, v] = tr2angvec(t)
0029 
0030     qs = sqrt(trace(t)+1)/2.0;
0031     qs
0032     kx = t(3,2) - t(2,3);    % Oz - Ay
0033     ky = t(1,3) - t(3,1);    % Ax - Nz
0034     kz = t(2,1) - t(1,2);    % Ny - Ox
0035 
0036     if (t(1,1) >= t(2,2)) & (t(1,1) >= t(3,3)) 
0037         kx1 = t(1,1) - t(2,2) - t(3,3) + 1;    % Nx - Oy - Az + 1
0038         ky1 = t(2,1) + t(1,2);            % Ny + Ox
0039         kz1 = t(3,1) + t(1,3);            % Nz + Ax
0040         add = (kx >= 0);
0041     elseif (t(2,2) >= t(3,3))
0042         kx1 = t(2,1) + t(1,2);            % Ny + Ox
0043         ky1 = t(2,2) - t(1,1) - t(3,3) + 1;    % Oy - Nx - Az + 1
0044         kz1 = t(3,2) + t(2,3);            % Oz + Ay
0045         add = (ky >= 0);
0046     else
0047         kx1 = t(3,1) + t(1,3);            % Nz + Ax
0048         ky1 = t(3,2) + t(2,3);            % Oz + Ay
0049         kz1 = t(3,3) - t(1,1) - t(2,2) + 1;    % Az - Nx - Oy + 1
0050         add = (kz >= 0);
0051     end
0052 
0053     if add
0054         kx = kx + kx1;
0055         ky = ky + ky1;
0056         kz = kz + kz1;
0057     else
0058         kx = kx - kx1;
0059         ky = ky - ky1;
0060         kz = kz - kz1;
0061     end
0062     v = unit([kx ky kz]);
0063     theta = 2*acos(qs);
0064 
0065     if nargout == 0
0066         fprintf('Rotation: %f rad x [%f %f %f]\n', theta, v(1), v(2), v(3));
0067     end

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