## Copyright (C) 2004-2011 David Legland <david.legland@grignon.inra.fr>
## Copyright (C) 2004-2011 INRA - CEPIA Nantes - MIAJ (Jouy-en-Josas)
## Copyright (C) 2012 Adapted to Octave by Juan Pablo Carbajal <carbajal@ifi.uzh.ch>
## 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
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## ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
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## SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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## -*- texinfo -*-
## @deftypefn {Function File} {@var{trans} =} createRotationOx (@var{theta})
## @deftypefnx {Function File} {@var{trans} =} createRotationOx (@var{origin},@var{theta})
## @deftypefnx {Function File} {@var{trans} =} createRotationOx (@var{x0},@var{y0},@var{z0},@var{theta})
##  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).
##
## @seealso{transforms3d, transformPoint3d, createRotationOy, createRotationOz}
## @end deftypefn

function trans = createRotationOx(varargin)

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

  # get input values
  if length(varargin)==1
      # only 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)==3
      # origin (x and y) and angle
      dx = varargin{1};
      dy = varargin{2};
      dz = varargin{3};
      theta = varargin{3};
  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;

endfunction
