function [] = GantryDisplay3(X, Xo, Ref)

Q = [0:0.1:1]' * 2*pi;
hold off
% observer


x = Xo(1);
q = Xo(2);
% cart
xc = [-0.2,0.2,0.2,-0.2,-0.2] + x;
yc = [0,0,0.2,0.2,0];
xm = x + sin(q);
ym = 0 - cos(q);
% ball
xb = 0.05*cos(Q) + xm;
yb = 0.05*sin(Q) + ym;
plot(xc, yc,'m',[x,xm],[0,ym],'m',xb, yb, 'm')
ylim([-2.5,0.5]);
hold on

% Plant

x = X(1);
q = X(2);
% cart
xc = [-0.2,0.2,0.2,-0.2,-0.2] + x;
yc = [0,0,0.2,0.2,0];
xm = x + sin(q);
ym = 0 - cos(q);
% ball
xb = 0.05*cos(Q) + xm;
yb = 0.05*sin(Q) + ym;
plot([-3,3],[0,0],'b-',xc, yc,'r-',[x,xm],[0,ym],'r-',xb, yb, 'r-',[Ref, Ref],[-0.1,0.1],'b')
ylim([-1.5,0.5]);
pause(0.01);
end