question: public synchronized void updateElevation ( QuadTree quadTree ) { FloatBuffer vertex = _meshData . getVertexBuffer ( ) ; int n = vertex . limit ( ) ; Landscape landscape = Landscape . getInstance ( ) ; for ( int i = 0 ; i < n ; i += 3 ) { float x = vertex . get ( i ) ; float y = vertex . get ( i + 1 ) ; double z = landscape . getZ ( x , y ) + 0.1 ; if ( ! Double . isNaN ( z ) ) { vertex . put ( i + 2 , ( float ) z ) ; } } }
target:  Update the elevation when the landscape changes.