createScaling3d(varargin)

function trans = createScaling3d(varargin)
%CREATESCALING3D Create the 4x4 matrix of a 3D scaling
%
%   TRANS = createScaling3d(S);
%   returns the scaling transform corresponding to a scaling factor S in
%   each direction. S can be a scalar, or a 1x3 vector containing the
%   scaling factor in each direction.
%
%   TRANS = createScaling3d(SX, SY, SZ);
%   returns the scaling transform corresponding to a different scaling
%   factor in each direction.
%
%   The returned matrix has the form :
%   [SX  0  0  0]
%   [ 0 SY  0  0]
%   [ 0  0 SZ  0]
%   [ 0  0  0  0]
%
%   See also:
%   transforms3d, transformPoint3d, transformVector3d, createTranslation3d,
%   createRotationOx, createRotationOy, createRotationOz
%
%   ---------
%   author : David Legland 
%   INRA - TPV URPOI - BIA IMASTE
%   created the 20/04/2006.
%

%   HISTORY
%   25/11/2008 rename from scale3d to scaling3d
%   30/04/2009 rename to createScaling3d


% process input parameters
if isempty(varargin)
    % assert uniform scaling in each direction
    sx = 1;
    sy = 1;
    sz = 1;
elseif length(varargin)==1
    % only one argument
    var = varargin{1};
    if length(var)==1
        % same scaling factor in each direction
        sx = var;
        sy = var;
        sz = var;
    elseif length(var)==3
        % scaling is a vector, giving different scaling in each direction
        sx = var(1);
        sy = var(2);
        sz = var(3);
    else
        error('wrong size for first parameter of "createScaling3d"');
    end
elseif length(varargin)==3
    % 3 arguments, giving scaling in each direction
    sx = varargin{1};
    sy = varargin{2};
    sz = varargin{3};
else
    error('wrong number of arguments for "createScaling3d"');
end

% create the scaling matrix
trans = [sx 0 0 0;0 sy 0 0;0 0 sz 0;0 0 0 1];