function [H]=drop_thinwalls(h,hx,hy,periodic)
%
% Returns the depths at T points based on T, U and V points.
%
% e.g.
%      H=drop_thinwalls(H2,Hx2,Hy2);

if size(h)~=size(hx) | size(h)~=size(hy)
 error('Arguments must all be the same size!\n');
end

[nx,ny]=size(h);

% Fill-up cell-centers where all sides are higher
Hsides=min( hx, hx([2:end 1],:,:) );
Hsides=min( Hsides, hy );
Hsides=min( Hsides, hy(:,[2:end end],:) );
H=max( h, Hsides );

%H=h;
for jj=1:ny;
 jp=min(ny,jj+1);
 jm=max(1,jj-1);
 for ii=1:nx;
  if periodic==1
   ip=mod(ii,nx)+1;
   im=mod(ii-2+nx,nx)+1;
  else
   ip=min(nx,ii+1);
   im=max(1,ii-1);
  end

  hp=H(ii,jj);
  hm=H(im,jj);
  ho=hx(ii,jj);
  if ho>max(hm,hp)
   if hm<hp
    H(ii,jj)=ho;
   else
    H(im,jj)=ho;
   end
  end

  hp=H(ii,jj);
  hm=H(ii,jm);
  ho=hy(ii,jj);
  if ho>max(hm,hp)
   if hm<hp
    H(ii,jj)=ho;
   else
    H(ii,jm)=ho;
   end
  end

 end
end