1## Copyright (C) 2021 David Legland
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27
28function trans = createRotationOx(varargin)
29%CREATEROTATIONOX Create the 4x4 matrix of a 3D rotation around x-axis.
30%
31%   TRANS = createRotationOx(THETA);
32%   Returns the transform matrix corresponding to a rotation by the angle
33%   THETA (in radians) around the Ox axis. A rotation by an angle of PI/2
34%   would transform the vector [0 1 0] into the vector [0 0 1].
35%
36%   The returned matrix has the form:
37%   [1      0            0      0]
38%   [0  cos(THETA) -sin(THETA)  0]
39%   [0  sin(THETA)  cos(THETA)  0]
40%   [0      0            0      1]
41%
42%   TRANS = createRotationOx(ORIGIN, THETA);
43%   TRANS = createRotationOx(X0, Y0, Z0, THETA);
44%   Also specifies origin of rotation. The result is similar as performing
45%   translation(-X0, -Y0, -Z0), rotation, and translation(X0, Y0, Z0).
46%
47%   See also:
48%   transforms3d, transformPoint3d, createRotationOy, createRotationOz
49%
50
51%   ---------
52%   author : David Legland
53%   INRA - TPV URPOI - BIA IMASTE
54%   created the 18/02/2005.
55%
56
57%   HISTORY
58%   24/11/2008 changed convention for angle
59%   22/04/2009 rename as createRotationOx
60
61
62% default values
63dx = 0;
64dy = 0;
65dz = 0;
66theta = 0;
67
68% get input values
69if length(varargin) == 1
70    % only one argument -> rotation angle
71    theta = varargin{1};
72
73elseif length(varargin) == 2
74    % origin point (as array) and angle
75    var = varargin{1};
76    dx = var(1);
77    dy = var(2);
78    dz = var(3);
79    theta = varargin{2};
80
81elseif length(varargin) == 4
82    % origin (x and y) and angle
83    dx = varargin{1};
84    dy = varargin{2};
85    dz = varargin{3};
86    theta = varargin{4};
87end
88
89% compute coefs
90cot = cos(theta);
91sit = sin(theta);
92
93% create transformation
94trans = [...
95    1 0 0 0;...
96    0 cot -sit 0;...
97    0 sit cot 0;...
98    0 0 0 1];
99
100% add the translation part
101t = [1 0 0 dx;0 1 0 dy;0 0 1 dz;0 0 0 1];
102trans = t * trans / t;
103