protected void cacheTerrainTransforms() {
        for (int i = children.size(); --i >= 0;) {
            Spatial child = children.get(i);
            if (child instanceof TerrainQuad) {
                ((TerrainQuad) child).cacheTerrainTransforms();
            } else if (child instanceof TerrainPatch) {
                ((TerrainPatch) child).cacheTerrainTransforms();
            }
        }
    }
Caches the transforms (except rotation) so the LOD calculator,
which runs on a separate thread, can access them safely.
jme3-terrain/src/main/java/com/jme3/terrain/geomipmap/TerrainQuad.java