Fitting rocks to geogrid

Hi everyone, I need helps on my project on Matlab.

My project is about right placement of geogrids. Geogrid is a material that improve stability of the ground. In the ground, I will have randomly shaped rocks, and to have right placement for my geogrid, rocks should be exact fit in spacing. Because when we try to pull out geogrid, rocks must be prevent it. But if rocks don't fit in grid, then pulling out geogrids will be so easy and geogrids will become useless. To sum up, I will try to get best fitting positions of rocks in to geogrid.

So when I go a ground and take dimension of aggregas, then I can came up a fitting positions of it with this matlab codes. Then I can decide where should I place my geogrid.

At the end, I need to get a visual like this;

Now, I just define a rock shape with this code;

   % My Rock
  x = randn(1000,1);
  y = randn(1000,1);
  z = randn(1000,1);
  % Alpha Shape and plot
  as = alphaShape(x,y,z,4);
  plot(as,'FaceColor',[218 136 86]./255,'EdgeAlpha',0)
  title('My Rock')
  lighting gouraud
  light('Position',[2 -4 2],'Style','local')

Thank you for your help!