function rotMat = matRad_getRotationMatrix(gantryAngle,couchAngle,system)
% matRad function to return the rotation / transformation matrix 
% for gantry and/or couch rotation. The Rotation matrix stands for a (1)
% counter-clockwise, (2) active rotation in the patient coordinate system
% that is performed on a (4) column vector (by premultiplying the matrix). 
% Per change of one of these directions a matrix transpose of the returned 
% matrix is required.
% 
% 
% call
%  rotMat = matRad_getRotationMatrix(gantryAngle,couchAngle,type,system)
%
% input
%   gantryAngle:    beam/gantry angle
%   couchAngle:     couch angle 
%
%   system:         optional coordinate system the transformation matrix is
%                   requested for. So far, only the default option 'LPS' is
%                   supported (right handed system).
%
% output
%   rotMat:         3x3 matrix that performs an active rotation around the 
%                   patient system origin via rotMat * x
%
% References
%   https://en.wikipedia.org/wiki/Rotation_matrix (2017, Mar 1)
%
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% Copyright 2015 the matRad development team. 
% 
% This file is part of the matRad project. It is subject to the license 
% terms in the LICENSE file found in the top-level directory of this 
% distribution and at https://github.com/e0404/matRad/LICENSES.txt. No part 
% of the matRad project, including this file, may be copied, modified, 
% propagated, or distributed except according to the terms contained in the 
% LICENSE file.
%
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% Parse arguments
%We need at least two and max 3 input arguments
narginchk(2,3);

% Coordinate System (only LPS so far)
if nargin < 3
    system = 'LPS';
end

%% Set Up requested Rotation Matrix
switch system
    case 'LPS'
        %The LPS system is right-handed, gantry rotates counter-clockwise 
        %around z and couch rotates counter-clockwise around y
        
        %active, counter-clockwise rotation Matrix for Gantry around z 
        %with pre-multiplication of the matrix (R*x)
        %Note: Gantry rotation is physically an active rotation of a beam 
        %vector around the target / isocenterin the patient coordinate
        %system
        R_Gantry = [cosd(gantryAngle)  -sind(gantryAngle)  0; ...
            sind(gantryAngle)    cosd(gantryAngle)  0; ...
            0                            0           1];
        
        %active, counter-clockwise rotation for couch around y
        %with pre-multiplication of the matrix (R*x)
        %Note: Couch rotation is physically a passive rotation of the 
        %patient system around the beam target point / isocenter
        R_Couch = [cosd(couchAngle) 0 sind(couchAngle); ...
            0 1 0; ...
            -sind(couchAngle)    0    cosd(couchAngle)];
    otherwise
        error('matRad only supports LPS system so far');
end

rotMat = R_Couch*R_Gantry;

end

