Concave decay/pruning

We will now see how the rule can be modified further to produce decay/pruning of the internal volume areas

Local rule:

    Delete random voxels over the whole structure (sparse)

    Iterate all positions in vG

    - If a voxel is found that is adjacent to air :

          Calculate the sum of voxels inside a radius R

          Based on this sum decide if the voxel surface is concave

          - If concave :

                Remove the voxel

We notice how internal walls are formed, and that the decay process converge (top fig).