private int findQuadrant(int x, int y) {
        int split = (size + 1) >> 1;
        int quads = 0;
        if (x < split && y < split)
            quads |= 1;
        if (x < split && y >= split - 1)
            quads |= 2;
        if (x >= split - 1 && y < split)
            quads |= 4;
        if (x >= split - 1 && y >= split - 1)
            quads |= 8;
        return quads;
    }
gets an interpolated value at the specified point
jme3-terrain/src/main/java/com/jme3/terrain/geomipmap/TerrainQuad.java