This GPU based script draws ui,n/2 cross-section after
one multigrid V-cycle with the reduction level = 5
and "deep" relaxation iterations 2rel. Boundaries are fixed
fi,j = sin(πi/n) sin(πj/n)
To get fixed boundaries on k×k texture (with periodic boundaries) we render
(-1 + 2/k, -1 + 2/k, 1, -1 + 2/k, -1 + 2/k, 1, 1, 1)
square (see the page source for detaile).
Simulations on GPUupdated 25 July 2012