function points_post(p)
% display vertices of a geometric figure defined 
% by points, p, in homogeneous coordinates where:
%   p(i,j):  i=point; j=coord (1=x,2=y,3=z,4=h)
%
x=p(:,1);
y=p(:,2);
hold on;
plot(x,y,'o');
hold off;
