Code covered by the BSD License

# geom2d

### David Legland (view profile)

13 Jun 2005 (Updated )

Geometry library for matlab. Performs geometric computations on points, lines, circles, polygons...

hexagonalGrid(bounds, origin, size, varargin)
```function varargout = hexagonalGrid(bounds, origin, size, varargin)
%HEXAGONALGRID Generate hexagonal grid of points in the plane.
%
%   usage
%   PTS = hexagonalGrid(BOUNDS, ORIGIN, SIZE)
%   generate points, lying in the window defined by BOUNDS (=[xmin ymin
%   xmax ymax]), starting from origin with a constant step equal to size.
%   SIZE is constant and is equals to the length of the sides of each
%   hexagon.
%
%   TODO: add possibility to use rotated grid
%
%   ---------
%
%   author : David Legland
%   INRA - TPV URPOI - BIA IMASTE
%   created the 06/08/2005.
%
size = size(1);
dx = 3*size;
dy = size*sqrt(3);

% consider two square grids with different centers
pts1 = squareGrid(bounds, origin + [0 0],        [dx dy], varargin{:});
pts2 = squareGrid(bounds, origin + [dx/3 0],     [dx dy], varargin{:});
pts3 = squareGrid(bounds, origin + [dx/2 dy/2],  [dx dy], varargin{:});
pts4 = squareGrid(bounds, origin + [-dx/6 dy/2], [dx dy], varargin{:});

% gather points
pts = [pts1;pts2;pts3;pts4];

% eventually compute also edges, clipped by bounds
% TODO : manage generation of edges
if nargout>1
edges = zeros([0 4]);
x0 = origin(1);
y0 = origin(2);

% find all x coordinate
x1 = bounds(1) + mod(x0-bounds(1), dx);
x2 = bounds(3) - mod(bounds(3)-x0, dx);
lx = (x1:dx:x2)';

% horizontal edges : first find y's
y1 = bounds(2) + mod(y0-bounds(2), dy);
y2 = bounds(4) - mod(bounds(4)-y0, dy);
ly = (y1:dy:y2)';

% number of points in each coord, and total number of points
ny = length(ly);
nx = length(lx);

if bounds(1)-x1+dx<size
disp('intersect bounding box');
end

if bounds(3)-x2<size
disp('intersect 2');
edges = [edges;repmat(x2, [ny 1]) ly repmat(bounds(3), [ny 1]) ly];
x2 = x2-dx;
lx = (x1:dx:x2)';
nx = length(lx);
end

for i=1:length(ly)
ind = (1:nx)';
tmpEdges(ind, 1) = lx;
tmpEdges(ind, 2) = ly(i);
tmpEdges(ind, 3) = lx+size;
tmpEdges(ind, 4) = ly(i);
edges = [edges; tmpEdges];
end

end

% process output arguments
if nargout>0
varargout{1} = pts;

if nargout>1
varargout{2} = edges;
end
end```