densifyPolygon

DENSIFYPOLYGON Add several points on each edge of the polygon.

   POLY2 = densifyPolygon(POLY, N)
   POLY is a NV-by-2 array containing polygon coordinates. The function
   iterates on polygon edges, divides it into N subedges (by inserting N-1
   new vertices on each edges), and return the resulting polygon.
   The new polygon POLY has therefore N*NV vertices.

   Example
     % Densifies a simple polygon
     poly = [0 0 ; 10 0;5 10;15 15;5 20;-5 10];
     poly2 = densifyPolygon(poly, 10);
     figure; drawPolygon(poly); axis equal
     hold on; drawPoint(poly2);

   See also
     drawPolygon, edgeToPolyline


 ------
 Author: David Legland
 e-mail: david.legland@grignon.inra.fr
 Created: 2011-11-25,    using Matlab 7.9.0.529 (R2009b)
 Copyright 2011 INRA - Cepia Software Platform.

0001 function poly2 = densifyPolygon(poly, N)
0002 %DENSIFYPOLYGON Add several points on each edge of the polygon.
0003 %
0004 %   POLY2 = densifyPolygon(POLY, N)
0005 %   POLY is a NV-by-2 array containing polygon coordinates. The function
0006 %   iterates on polygon edges, divides it into N subedges (by inserting N-1
0007 %   new vertices on each edges), and return the resulting polygon.
0008 %   The new polygon POLY has therefore N*NV vertices.
0009 %
0010 %   Example
0011 %     % Densifies a simple polygon
0012 %     poly = [0 0 ; 10 0;5 10;15 15;5 20;-5 10];
0013 %     poly2 = densifyPolygon(poly, 10);
0014 %     figure; drawPolygon(poly); axis equal
0015 %     hold on; drawPoint(poly2);
0016 %
0017 %   See also
0018 %     drawPolygon, edgeToPolyline
0019 %
0020 %
0021 % ------
0022 % Author: David Legland
0023 % e-mail: david.legland@grignon.inra.fr
0024 % Created: 2011-11-25,    using Matlab 7.9.0.529 (R2009b)
0025 % Copyright 2011 INRA - Cepia Software Platform.
0026 
0027 % number of vertices, and of edges
0028 Nv = size(poly, 1);
0029 
0030 % number of vertices in new polygon
0031 N2 = N * Nv;
0032 poly2 = zeros(N2, 2);
0033 
0034 % iterate on polygon edges
0035 for i = 1:Nv
0036     % extract current edge
0037     v1 = poly(i, :);
0038     v2 = poly(mod(i, Nv) + 1, :);
0039     
0040     % convert current edge to polyline
0041     newVertices = edgeToPolyline([v1 v2], N);
0042     
0043     % indices of current polyline to resulting polygon
0044     i1 = (i-1)*N + 1;
0045     i2 = i * N;
0046     
0047     % fill up polygon
0048     poly2(i1:i2, :) = newVertices(1:end-1, :);
0049 end
0050