Help ! Metaballs to surface in between network of trees

Hello,

We are new to grasshopper but we think it may be very useful for the project we are working on at school, we hope that some of you can give us a hand with a couple issues we are having trouble getting answers for on the web.

Our goal is to install a scientific research lab in a forest to study the proliferation of a deadly tree disease so we would like to design a sort of big cocoon that is in part randomly generated and that would wrap around the trees inside it similar to how the disease proliferates through the forest... Unfortunately, we are having a few problems modeling it on grasshopper, here are our questions :

First off we have generated a grid on which we have attached vertical lines that represent the trees of the forest we are working on, we have also modeled a grid that is the dual to the first one (links the centers of the cells of the first grid together to form another grid). We have generated points of random z coordinates that follow the x and y coordinates of the second grid, and we have applied metaballs to those random points.

 1. We would like to know how to create a surface from the curves generated by the metaballs in my grasshopper file ?

2. We would like to know if it is possible to push the surface away from the lines on the grid, as if there was a magnetic field pushing matter away from them ? we are hoping it would look a bit like this (the black lines being the trees and the big grey volume the surface wrapping around the trees, avoiding them) :

If you have any ideas of a better way of representing what we want to model please let me know (or if it isn't well explained please call me out on that). What we like about our grasshopper file for now is that you can kind of change the sizes of the metaballs pretty easily, the fact that they are randomly generated and smoothly blend together, but if you know a better way of achieving a similar result please let us know!

A few pics of what it looks like as of now :

Here is our grasshopper file attached, to generate the metaballs you just have to make a point in the center of the very first cell of the larger grid, so the corner of the second grid, and link it to the point in the grasshopper file.

Thanks, Sarah, Vincent and Nicholas