@Override
    public int getMaxLod() {
        if (maxLod < 0)
            maxLod = Math.max(1, (int) (FastMath.log(size-1)/FastMath.log(2)) -1); // -1 forces our minimum of 4 triangles wide

        return maxLod;
    }
Removes any cached references this terrain is holding, in particular
the TerrainPatch's neighbour references.
This is called automatically when the root terrainQuad is detached from
its parent or if setParent(null) is called.
jme3-terrain/src/main/java/com/jme3/terrain/geomipmap/TerrainQuad.java