drawSphericalTriangle

DRAWSPHERICALTRIANGLE Draw a triangle on a sphere.

   drawSphericalTriangle(SPHERE, PT1, PT2, PT3);
   Draws the spherical triangle defined by the three input 3D points and
   the reference sphere. 
   Points are given as 3D points, and are projected onto the sphere. The
   order of the points is not relevant. 

   drawSphericalTriangle(SPHERE, PT1, PT2, PT3, OPTIONS);
   Allows to specify plot options for spherical edges, in the form of
   parameter name-value pairs.

   Example
     % Draw a sphere and a spherical triangle on it
     s = [0 0 0 2];
     pts = [1 0 0;0 -1 0;0 0 1];
     drawSphere(s); hold on;
     drawSphericalTriangle(s, pts(1,:), pts(2,:), pts(3,:), 'linewidth', 2);
     view(3); axis equal;

   See also
   drawSphere, fillSphericalTriangle, drawSphericalPolygon,
   drawSphericalEdge

   ---------
   author : David Legland
   INRA - TPV URPOI - BIA IMASTE
   created the 22/02/2005

0001 function varargout = drawSphericalTriangle(sphere, p1, p2, p3, varargin)
0002 %DRAWSPHERICALTRIANGLE Draw a triangle on a sphere.
0003 %
0004 %   drawSphericalTriangle(SPHERE, PT1, PT2, PT3);
0005 %   Draws the spherical triangle defined by the three input 3D points and
0006 %   the reference sphere.
0007 %   Points are given as 3D points, and are projected onto the sphere. The
0008 %   order of the points is not relevant.
0009 %
0010 %   drawSphericalTriangle(SPHERE, PT1, PT2, PT3, OPTIONS);
0011 %   Allows to specify plot options for spherical edges, in the form of
0012 %   parameter name-value pairs.
0013 %
0014 %   Example
0015 %     % Draw a sphere and a spherical triangle on it
0016 %     s = [0 0 0 2];
0017 %     pts = [1 0 0;0 -1 0;0 0 1];
0018 %     drawSphere(s); hold on;
0019 %     drawSphericalTriangle(s, pts(1,:), pts(2,:), pts(3,:), 'linewidth', 2);
0020 %     view(3); axis equal;
0021 %
0022 %   See also
0023 %   drawSphere, fillSphericalTriangle, drawSphericalPolygon,
0024 %   drawSphericalEdge
0025 %
0026 %   ---------
0027 %   author : David Legland
0028 %   INRA - TPV URPOI - BIA IMASTE
0029 %   created the 22/02/2005
0030 %
0031 
0032 %   HISTORY
0033 %   2007-06-27 manage spheres other than origin
0034 %   2008-10-30 replace intersectPlaneLine by intersectLinePlane
0035 %   2012-02-09 put drawing code into the 'drawSphericalEdge' function
0036 %   2012-10-24 add holding facility, updtate doc
0037 
0038 
0039 % extract data of the sphere
0040 ori = sphere(:, 1:3);
0041 
0042 % extract direction vectors for each point
0043 v1  = normalizeVector3d(p1 - ori);
0044 v2  = normalizeVector3d(p2 - ori);
0045 v3  = normalizeVector3d(p3 - ori);
0046 
0047 % keep hold state of current axis
0048 h = ishold;
0049 
0050 % draw each spherical edge
0051 hold on;
0052 h1 = drawSphericalEdge(sphere, [v1 v2], varargin{:});
0053 h2 = drawSphericalEdge(sphere, [v2 v3], varargin{:});
0054 h3 = drawSphericalEdge(sphere, [v3 v1], varargin{:});
0055 
0056 % return to previous hold state if needed
0057 if ~h
0058     hold off;    
0059 end
0060 
0061 if nargout > 0
0062     varargout = {h1, h2, h3};
0063 end