public int getTotalSize() {
        return totalSize;
    }
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