## Copyright (C) 2021 David Legland
## All rights reserved.
## 
## Redistribution and use in source and binary forms, with or without
## modification, are permitted provided that the following conditions are met:
## 
##     1 Redistributions of source code must retain the above copyright notice,
##       this list of conditions and the following disclaimer.
##     2 Redistributions in binary form must reproduce the above copyright
##       notice, this list of conditions and the following disclaimer in the
##       documentation and/or other materials provided with the distribution.
## 
## THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ''AS IS''
## AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
## IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
## ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
## ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
## DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
## SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
## CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
## OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
## OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
## 
## The views and conclusions contained in the software and documentation are
## those of the authors and should not be interpreted as representing official
## policies, either expressed or implied, of the copyright holders.

function trans = createRotationOx(varargin)
%CREATEROTATIONOX Create the 4x4 matrix of a 3D rotation around x-axis.
%
%   TRANS = createRotationOx(THETA);
%   Returns the transform matrix corresponding to a rotation by the angle
%   THETA (in radians) around the Ox axis. A rotation by an angle of PI/2
%   would transform the vector [0 1 0] into the vector [0 0 1].
%
%   The returned matrix has the form:
%   [1      0            0      0]
%   [0  cos(THETA) -sin(THETA)  0]
%   [0  sin(THETA)  cos(THETA)  0]
%   [0      0            0      1]
%
%   TRANS = createRotationOx(ORIGIN, THETA);
%   TRANS = createRotationOx(X0, Y0, Z0, THETA);
%   Also specifies origin of rotation. The result is similar as performing
%   translation(-X0, -Y0, -Z0), rotation, and translation(X0, Y0, Z0).
%
%   See also:
%   transforms3d, transformPoint3d, createRotationOy, createRotationOz
%

%   ---------
%   author : David Legland 
%   INRA - TPV URPOI - BIA IMASTE
%   created the 18/02/2005.
%

%   HISTORY
%   24/11/2008 changed convention for angle
%   22/04/2009 rename as createRotationOx


% default values
dx = 0;
dy = 0;
dz = 0;
theta = 0;

% get input values
if length(varargin) == 1
    % only one argument -> rotation angle
    theta = varargin{1};
    
elseif length(varargin) == 2
    % origin point (as array) and angle
    var = varargin{1};
    dx = var(1);
    dy = var(2);
    dz = var(3);
    theta = varargin{2};
    
elseif length(varargin) == 4
    % origin (x and y) and angle
    dx = varargin{1};
    dy = varargin{2};
    dz = varargin{3};
    theta = varargin{4};
end

% compute coefs
cot = cos(theta);
sit = sin(theta);

% create transformation
trans = [...
    1 0 0 0;...
    0 cot -sit 0;...
    0 sit cot 0;...
    0 0 0 1];

% add the translation part
t = [1 0 0 dx;0 1 0 dy;0 0 1 dz;0 0 0 1];
trans = t * trans / t;