bisector

BISECTOR Return the bisector of two lines, or 3 points.

   RAY = bisector(LINE1, LINE2);
   create the bisector of the two lines, given as [x0 y0 dx dy].

   RAY = bisector(P1, P2, P3);
   create the bisector of lines (P2 P1) and (P2 P3).

   The result has the form [x0 y0 dx dy], with [x0 y0] being the origin
   point ans [dx dy] being the direction vector, normalized to have unit
   norm.
   
   See also:
   lines2d, rays2d

   ---------
 Author: David Legland
 e-mail: david.legland@grignon.inra.fr
 created the 31/10/2003.
 Copyright 2010 INRA - Cepia Software Platform.

0001 function ray = bisector(varargin)
0002 %BISECTOR Return the bisector of two lines, or 3 points.
0003 %
0004 %   RAY = bisector(LINE1, LINE2);
0005 %   create the bisector of the two lines, given as [x0 y0 dx dy].
0006 %
0007 %   RAY = bisector(P1, P2, P3);
0008 %   create the bisector of lines (P2 P1) and (P2 P3).
0009 %
0010 %   The result has the form [x0 y0 dx dy], with [x0 y0] being the origin
0011 %   point ans [dx dy] being the direction vector, normalized to have unit
0012 %   norm.
0013 %
0014 %   See also:
0015 %   lines2d, rays2d
0016 %
0017 %   ---------
0018 % Author: David Legland
0019 % e-mail: david.legland@grignon.inra.fr
0020 % created the 31/10/2003.
0021 % Copyright 2010 INRA - Cepia Software Platform.
0022 
0023 %   HISTORY
0024 %   2005-07-07 add bisector of 3 points
0025 %   2010-11-05 ode cleanup
0026 
0027 if length(varargin)==2
0028     % two lines
0029     line1 = varargin{1};
0030     line2 = varargin{2};
0031     
0032     point = intersectLines(line1, line2);    
0033     
0034 elseif length(varargin)==3
0035     % three points
0036     p1 = varargin{1};
0037     p2 = varargin{2};
0038     p3 = varargin{3};
0039 
0040     line1 = createLine(p2, p1);
0041     line2 = createLine(p2, p3);
0042     point = p2;
0043     
0044 elseif length(varargin)==1
0045     % three points, given in one array
0046     var = varargin{1};
0047     p1 = var(1, :);
0048     p2 = var(2, :);
0049     p3 = var(3, :);
0050 
0051     line1 = createLine(p2, p1);
0052     line2 = createLine(p2, p3);
0053     point = p2;
0054 end
0055 
0056 % compute line angles
0057 a1 = lineAngle(line1);
0058 a2 = lineAngle(line2);
0059 
0060 % compute bisector angle (angle of first line + half angle between lines)
0061 angle = mod(a1 + mod(a2-a1+2*pi, 2*pi)/2, pi*2);
0062 
0063 % create the resulting ray
0064 ray = [point cos(angle) sin(angle)];