function [pn]=norma_pre(p)
%
% [pn]=norma_post(p)
% pn has one 4-element column for each point

[sprow spcol]=size(p);

for n=1:spcol
   if p(4,n)~=0 
       pn(:,n)=p(:,n)/p(4,n); 
   end
end