function [x,y,jc] = LMobjectpolygon(annotation, name);
% [x,y] = LMobjectpolygon(annotation, name) returns all the polygons that
% belong to object class 'name'. Is it an array Ninstances*Nvertices

if isfield(annotation, 'object')
    if nargin == 1
        jc = 1:length(annotation.object);
    else
        jc = LMobjectindex(annotation, name);
    end

    Nobjects = length(jc);
    if Nobjects == 0
        x = []; y =[];
    else
        for n = 1:Nobjects
            [x{n},y{n}] = getLMpolygon(annotation.object(jc(n)).polygon);
        end
    end
else
    x = [];
    y = [];
    jc = [];
end