[Nek5000-users] "convert" a given u_x(i, j, k) in an uniform grid to a vx(i, j, k, e) in a GLL grid ??

[nek5000-users at lists.mcs.anl.gov]

Hi neks,

I am trying to set a random turbulent velocity field as an initial 
condition for my simulation. The domaine is a cube 2pi * 2pi * 2pi and  
nelx = nely=nelz=32 (lx1=12)

And i was wondering if they are some routines for "project" a given 
value of  u_x(i,j,k) (x component of the velocity field in a regular 
grid) to vx(i,j,k,e) (x component of the velocity field on GLL grid) ??
In one of the emails you said "given i,j,k,e,p, one can find the 
associated (x,y,z) point. The inverse problem of finding i,j,k,e,p for a 
given (x,y,z) value is much more difficult (and expensive), but we have 
routines to handle this.)"
Can you tell me more about this ??
B.regards
Can