I am working on FLASH datasets with particles. I have some self-defined fields (specifically Lorentz factors) that are stored in the particle data and would like to map them onto the mesh grid. I've been trying the "add_deposited_particle_field" that is in the dev version. Currently I use the "cic" method, in which a particle will populate the nearby 8 cells (in 3D). However, since my particles are sparser than the mesh cells, many of the cells do not have particles nearby and thus are empty. 

I would like to find a way to interpolate for those empty cells, i.e. to smooth the particle field. Are there any suggestions or directions I should look into?

It would also be very helpful if I can get the list of N nearest neighbor particles for each cell. I've looked into the nearest neighbor function

But it seems that it is implemented only for octree-based data objects (and can only perform in a particle-to-particle fashion?), while FLASH data are loaded into yt as "patch-based" data object.

Is there any function that can get the nearest particle neighbors of each cell?

Thank you,

Yi-Hao