sphereMesh

 Create a 3D mesh representing a sphere.

   [V, F] = sphereMesh(S)
   Creates a 3D mesh representing the sphere S given by [xc yc zy r].

   [V, F] = sphereMesh();
   Assumes sphere is the unit sphere centered at the origin.

   [V, F] = sphereMesh(S, 'nTheta', NT, 'nPhi', NP);
   Specifies the number of discretisation steps for the meridians and the
   parallels. Default values are nTheta = 16 and nPhi = 32.


   Example
     s = [10 20 30 40];
     [v, f] = sphereMesh(s);
     drawMesh(v, f);
     view(3); axis equal; light; lighting gouraud;

   See also
     meshes3d, drawSphere, ellipsoidMesh, cylinderMesh, surfToMesh

0001 function varargout = sphereMesh(sphere, varargin)
0002 % Create a 3D mesh representing a sphere.
0003 %
0004 %   [V, F] = sphereMesh(S)
0005 %   Creates a 3D mesh representing the sphere S given by [xc yc zy r].
0006 %
0007 %   [V, F] = sphereMesh();
0008 %   Assumes sphere is the unit sphere centered at the origin.
0009 %
0010 %   [V, F] = sphereMesh(S, 'nTheta', NT, 'nPhi', NP);
0011 %   Specifies the number of discretisation steps for the meridians and the
0012 %   parallels. Default values are nTheta = 16 and nPhi = 32.
0013 %
0014 %
0015 %   Example
0016 %     s = [10 20 30 40];
0017 %     [v, f] = sphereMesh(s);
0018 %     drawMesh(v, f);
0019 %     view(3); axis equal; light; lighting gouraud;
0020 %
0021 %   See also
0022 %     meshes3d, drawSphere, ellipsoidMesh, cylinderMesh, surfToMesh
0023 %
0024 
0025 % ------
0026 % Author: David Legland
0027 % e-mail: david.legland@inra.fr
0028 % Created: 2012-10-25,    using Matlab 7.9.0.529 (R2009b)
0029 % Copyright 2012 INRA - Cepia Software Platform.
0030 
0031 if nargin == 0
0032     sphere = [0 0 0 1];
0033 end
0034 
0035 % number of meridians
0036 nPhi    = 32;
0037     
0038 % number of parallels
0039 nTheta  = 16;
0040 
0041 % process input arguments
0042 while length(varargin) > 1
0043     paramName = varargin{1};
0044     switch lower(paramName)
0045         case 'ntheta', nTheta = varargin{2};
0046         case 'nphi', nPhi = varargin{2};
0047         otherwise
0048             error(['Could not recognise parameter: ' paramName]);
0049     end
0050     varargin(1:2) = [];
0051 end
0052 
0053 % extract sphere data
0054 xc = sphere(:,1);
0055 yc = sphere(:,2);
0056 zc = sphere(:,3);
0057 r  = sphere(:,4);
0058 
0059 
0060 % compute spherical coordinates
0061 theta   = linspace(0, pi, nTheta+1);
0062 phi     = linspace(0, 2*pi, nPhi+1);
0063 
0064 % convert to cartesian coordinates
0065 sintheta = sin(theta);
0066 x = xc + cos(phi') * sintheta * r;
0067 y = yc + sin(phi') * sintheta * r;
0068 z = zc + ones(length(phi),1) * cos(theta) * r;
0069 
0070 % convert to FV mesh
0071 [vertices, faces] = surfToMesh(x, y, z, 'yperiodic', true);
0072 
0073 % format output
0074 varargout = formatMeshOutput(nargout, vertices, faces);