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## Copyright (C) 2024 David Legland
## All rights reserved.
##
## Redistribution and use in source and binary forms, with or without
## modification, are permitted provided that the following conditions are met:
##
## 1 Redistributions of source code must retain the above copyright notice,
## this list of conditions and the following disclaimer.
## 2 Redistributions in binary form must reproduce the above copyright
## notice, this list of conditions and the following disclaimer in the
## documentation and/or other materials provided with the distribution.
##
## THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ''AS IS''
## AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
## IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
## ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
## ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
## DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
## SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
## CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
## OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
## OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
##
## The views and conclusions contained in the software and documentation are
## those of the authors and should not be interpreted as representing official
## policies, either expressed or implied, of the copyright holders.
function varargout = sphereMesh(sphere, varargin)
%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
%
% ------
% Author: David Legland
% E-mail: david.legland@inrae.fr
% Created: 2012-10-25, using Matlab 7.9.0.529 (R2009b)
% Copyright 2012-2023 INRA - Cepia Software Platform
if nargin == 0
sphere = [0 0 0 1];
end
% number of meridians
nPhi = 32;
% number of parallels
nTheta = 16;
% process input arguments
while length(varargin) > 1
paramName = varargin{1};
switch lower(paramName)
case 'ntheta', nTheta = varargin{2};
case 'nphi', nPhi = varargin{2};
otherwise
error(['Could not recognise parameter: ' paramName]);
end
varargin(1:2) = [];
end
% extract sphere data
xc = sphere(:,1);
yc = sphere(:,2);
zc = sphere(:,3);
r = sphere(:,4);
% compute spherical coordinates
theta = linspace(0, pi, nTheta+1);
phi = linspace(0, 2*pi, nPhi+1);
% convert to cartesian coordinates
sintheta = sin(theta);
x = xc + cos(phi') * sintheta * r;
y = yc + sin(phi') * sintheta * r;
z = zc + ones(length(phi),1) * cos(theta) * r;
% convert to FV mesh
[vertices, faces] = surfToMesh(x, y, z, 'yperiodic', true);
% format output
varargout = formatMeshOutput(nargout, vertices, faces);
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