protected TerrainQuad findDownQuad() {
        boolean useFinder = false;
        if (getParent() == null || !(getParent() instanceof TerrainQuad)) {
            if (neighbourFinder == null)
                return null;
            else
                useFinder = true;
        }

        TerrainQuad pQuad = null;
        if (!useFinder)
            pQuad = (TerrainQuad) getParent();

        if (quadrant == 1)
            return pQuad.getQuad(2);
        else if (quadrant == 3)
            return pQuad.getQuad(4);
        else if (quadrant == 2) {
            TerrainQuad quad = pQuad.findDownQuad();
            if (quad != null)
                return quad.getQuad(1);
        } else if (quadrant == 4) {
            TerrainQuad quad = pQuad.findDownQuad();
            if (quad != null)
                return quad.getQuad(3);
        } else if (quadrant == 0) {
            // at the top quad
            if (useFinder) {
                TerrainQuad quad = neighbourFinder.getDownQuad(this);
                return quad;
            }
        }

        return null;
    }
lock or unlock the meshes of this terrain.
Locked meshes are uneditable but have better performance.
@param locked or unlocked
jme3-terrain/src/main/java/com/jme3/terrain/geomipmap/TerrainQuad.java