This program interpolates DNS data to a new grid using linear interpolation. It can run and store the interpolated data in a massively-parallel setting using MPI I/O. For now, it assumes two regular Cartesian grids with the file format of CaNS. Information about the boundary conditions of the system must be prescribed too. It is a cleaned up version of the routines used to create the initial conditions for particle-laden turbulent channel transport with 10^10 Eulerian grid points.