createEdge

CREATEEDGE Create an edge between two points, or from a line.

   The internal format for edge representation is given by coordinates of
   two points : [x1 y1 x2 y2].
   This function can serve as a line to edge converter.


   E = createEdge(P1, P2);
   Returns the edge between the two given points P1 and P2.
   
   E = createEdge(x0, y0, dx, dy);
   Returns the edge going through point (x0, y0) and with direction
   vector (dx,dy).

   E = createEdge(param);
   where param is an array of 4 values, creates the edge going through the
   point (param(1) param(2)), and with direction vector given by
   (param(3) param(4)).
   
   E = createEdge(LINE, D);
   create the edge contained in LINE, with same direction and start point,
   but with length given by D.


   Note: in all cases, parameters can be vertical arrays of the same
   dimension. The result is then an array of edges, of dimensions N-by-4.


   See also:
   edges2d, lines2d, drawEdge, clipEdge, createLine

0001 function edge = createEdge(varargin)
0002 %CREATEEDGE Create an edge between two points, or from a line.
0003 %
0004 %   The internal format for edge representation is given by coordinates of
0005 %   two points : [x1 y1 x2 y2].
0006 %   This function can serve as a line to edge converter.
0007 %
0008 %
0009 %   E = createEdge(P1, P2);
0010 %   Returns the edge between the two given points P1 and P2.
0011 %
0012 %   E = createEdge(x0, y0, dx, dy);
0013 %   Returns the edge going through point (x0, y0) and with direction
0014 %   vector (dx,dy).
0015 %
0016 %   E = createEdge(param);
0017 %   where param is an array of 4 values, creates the edge going through the
0018 %   point (param(1) param(2)), and with direction vector given by
0019 %   (param(3) param(4)).
0020 %
0021 %   E = createEdge(LINE, D);
0022 %   create the edge contained in LINE, with same direction and start point,
0023 %   but with length given by D.
0024 %
0025 %
0026 %   Note: in all cases, parameters can be vertical arrays of the same
0027 %   dimension. The result is then an array of edges, of dimensions N-by-4.
0028 %
0029 %
0030 %   See also:
0031 %   edges2d, lines2d, drawEdge, clipEdge, createLine
0032 %
0033 
0034 %   ---------
0035 %   author : David Legland
0036 %   INRA - TPV URPOI - BIA IMASTE
0037 %   created the 31/10/2003.
0038 %
0039 
0040 %   HISTORY
0041 %   18/02/2004 : add more possibilities to create edges, not only from 2
0042 %   points. Also add support for arrays.
0043 %   31/03/2004 : convert to [P1 P2] format
0044 
0045 if nargin == 1
0046     % Only one input parameter. It can be :
0047     % - line angle
0048     % - array of four parameters
0049     % TODO : add control for arrays of lines.
0050     var = varargin{1};
0051     
0052     if size(var, 2)==4
0053         % 4 parameters of the line in a single array.
0054         %edge = var;
0055         edge = zeros(size(var));
0056         edge(:, 1:2) = var(:,1:2);
0057         edge(:, 3:4) = edge(:, 1:2)+var(:,3:4);
0058     elseif size(var, 2)==1
0059         % 1 parameter : angle of the line, going through origin.
0060         edge = [zeros(size(var,1)) zeros(size(var,1)) cos(var) sin(var)];
0061     else
0062         error('wrong number of dimension for arg1 : can be 1 or 4');
0063     end
0064     
0065 elseif nargin == 2    
0066     % 2 input parameters. They can be :
0067     % - 2 points, then 2 arrays of 1*2 double,
0068     % - a line, and a distance.
0069     
0070     % extract the two arguments
0071     v1 = varargin{1};
0072     v2 = varargin{2};
0073     
0074     if size(v1, 2) == 2
0075         % first input parameter is first point, and second input is the
0076         % second point.
0077         %edge = [v1(:,1), v1(:,2), v2(:,1), v2(:,2)];
0078         edge = [v1 v2];
0079     else
0080         % first input parameter is a line, and second one a distance.
0081         angle = atan2(v1(:,4), v1(:,3));
0082         edge = [v1(:,1), v1(:,2), v1(:,1)+v2.*cos(angle), v1(:,2)+v2.*sin(angle)];
0083     end
0084     
0085 elseif nargin == 3
0086     % 3 input parameters :
0087     % first one is a point belonging to the line,
0088     % second and third ones are direction vector of the line (dx and dy).
0089     p = varargin{1};
0090     edge = [p(:,1) p(:,2) p(:,1)+varargin{2} p(:,2)+varargin{3}];
0091    
0092 elseif nargin == 4
0093     % 4 input parameters :
0094     % they are x0, y0 (point belonging to line) and dx, dy (direction
0095     % vector of the line).
0096     % All parameters should have the same size.
0097     edge = [varargin{1} varargin{2} varargin{1}+varargin{3} varargin{2}+varargin{4}];
0098 else
0099     error('Wrong number of arguments in ''createEdge'' ');
0100 end