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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 silhouette = meshSilhouette(v, f, varargin)
%MESHSILHOUETTE Compute the 2D outline of a 3D mesh on an arbitrary plane.
%
% ATTENTION: Very slow brute force approach! Keep the number of faces as
% low as possible.
%
% SILHOUETTE = meshSilhouette(MESH, PLANE)
% Calculates the silhouette (2D outline) of the MESH projected on the
% PLANE.
%
% SILHOUETTE = meshSilhouette(MESH) uses the x-y plane.
%
% SILHOUETTE = meshSilhouette(V, F, ...)
%
% SILHOUETTE = meshSilhouette(..., 'visu', 1) visualizes the results.
% By default the results are not visualized.
%
% Example:
% v = [5, 2, 6, 0, 3; 0, 2, 4, 2, 1; -5, -6, -6, -7, -9]';
% f = [1, 2, 4; 1, 5, 4; 1, 2, 5; 2, 3, 5; 2, 4, 3; 3, 4, 5];
% sil = meshSilhouette(v, f, rand(1,9),'visu',1);
%
% See also
% projPointOnPlane
%
% Source:
% Sean de Wolski - https://www.mathworks.com/matlabcentral/answers/68004
% ------
% Author: oqilipo
% E-mail: N/A
% Created: 2020-07-29
% Copyright 2020-2023
narginchk(1,5)
nargoutchk(0,1)
%% Parse inputs
% If first argument is a struct
if isstruct(v)
if nargin > 1
varargin=[{f} varargin{:}];
end
mesh = v;
[v, f] = parseMeshData(v);
else
mesh.vertices = v;
mesh.faces = f;
end
p = inputParser;
logParValidFunc = @(x) (islogical(x) || isequal(x,1) || isequal(x,0));
addOptional(p,'plane',[0 0 0 1 0 0 0 1 0],@isPlane)
addParameter(p,'visualization',false,logParValidFunc);
parse(p, varargin{:});
plane = p.Results.plane;
% Transform into the x-y plane
TFM = createBasisTransform3d('g', plane);
v = transformPoint3d(v,TFM);
% Initialize final polygon vectors
[px, py] = boundary(polyshape(v(f(1,:),1) ,v(f(1,:),2), 'Simplify',false));
for i = 2:size(f,1)
A = polyshape(v(f(i,:),1), v(f(i,:),2), 'Simplify',false);
B = polyshape(px, py, 'Simplify',false);
[px, py] = boundary(union(A,B));
end
% Transform back into the plane
silhouette = transformPoint3d([px,py,zeros(size(px))], inv(TFM));
if p.Results.visualization
figure('Color','w'); axH = axes(); axis(axH, 'equal', 'tight')
drawPolyline3d(axH, silhouette,'Color','r','LineWidth',3)
drawPlane3d(axH, plane,'FaceAlpha',0.5)
drawMesh(mesh,'FaceAlpha',0.5,'FaceColor','none')
axis(axH, 'equal')
camTar = nanmean(silhouette);
axH.CameraTarget = camTar;
axH.CameraPosition = camTar + ...
planeNormal(plane)*vectorNorm3d(axH.CameraPosition-axH.CameraTarget);
axH.CameraUpVector = plane(4:6);
xlabel(axH, 'x'); ylabel(axH, 'y'); zlabel(axH, 'z');
end
end
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