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geom3d

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geom3d

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19 Jun 2009 (Updated )

Library to handle 3D geometric primitives: create, intersect, display, and make basic computations

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demoVoronoiCell

Contents

function demoVoronoiCell(varargin)
%DEMOVORONOICELL Compute and display voronoi polyhedron using geom3d library
%
%   This demo show how to manipulate polyhedra, using matlab's voronoin
%   function and the geom3d library.
%
%   This demo generate some points in a unit cube, computes the 3D voronoi
%   diagram from the germs, and isolate the central cell.
%   This cell is a bounded polyhedron, with polygonal faces. For a better
%   representation of the polyhedron, coplanar faces are merged and a new
%   polyhedron is created and displayed.
%
%   Usage
%   demoVoronoiCell
%
%   See also
%   voronoin, delaunayn, convhulln
%   meshReduce, drawPolyhedron
%
%
% ------
% Author: David Legland
% e-mail: david.legland@grignon.inra.fr
% Created: 2009-06-22,    using Matlab 7.7.0.471 (R2008b)
% Copyright 2009 INRA - Cepia Software Platform.

Creation of germs

% germ of the cell of interest, in the center of the unit cube
germ0  = [.5 .5 .5];

% create random germs, and add corners of unit cube to ensure finiteness of
% voronoi pattern
[corners faces] = createCube; %#ok<NASGU>
germs   = [germ0;rand(10, 3);corners];

% dispay the germs
figure(1); clf; hold on;
drawPoint3d(germs);

% graphical settings
view(3);
axis equal;

Display Voronoi polyhedron associated with germ

% compute voronoi diagram in 3D using Matlab standard function
[V C]   = voronoin(germs);

% the polyhedron corresponding to first germ is given by vertices in C{1}
indVert = C{1};
vertices = V(indVert, :);

% triangular faces can be obtained from convhulln
K = convhulln(vertices);

% draw the polyhedron
drawPolyhedron(vertices, K);

Compute and display minimal polyhedron

% merge some faces to reduce total number of faces.
% new faces are 3D polygons
% K2 is a cell array, each cell containing a row vector with indices of
% 'points' corresponding to vertices of each face.
K2 = meshReduce(vertices, K);

% display the germs
figure(1); clf; hold on;
set(gcf, 'renderer', 'opengl');
drawPoint3d(germs);

% draw the polyhedron
drawPolyhedron(vertices, K2);

% graphical settings
view(3);
axis equal;

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