cull/dispatch trouble

Hi Everyone. I'm working on crystal-like 3D-grid, octahedron cells of which are based on point matrix. Idea is that i want to put inside of the grid some geometry (e.g. ramps, volumes) and points/octahedrons going to avoid this new geometry giving it free space.

I'm stuck when trying to dispatch points closest to 3D helix. The problem i think that number of measured distances is far bigger than number of points in matrix...

Please help me :)

Thanks in advance.