function circlemesh(r,t,N)
  [rr,tt] = meshgrid(r,t);
  [xx,yy] = pol2cart(tt,rr);
  z = exp(1i*pi*(-100:100)/100);
  N = N/norm(N(:),inf);
  plot(z), axis([-1 1 -1 1 -1 1]), axis off, hold on
  mesh(xx,yy,N)
  view(0,30), colormap(1e-6*[1 1 1]); axis square
  contour3(xx,yy,N-1,[-1 -1])
  plot3(real(z),imag(z),-abs(z))
endfunction