private void createMouseRay(GL2 gl, int x, int y) {

    int viewport[] = new int[4];
    double modelview[] = new double[16];
    double projection[] = new double[16];
    double rayStartPos[] = new double[4];
    double rayEndPos[] = new double[4];

    gl.glGetDoublev(GL2.GL_MODELVIEW_MATRIX, modelview, 0);
    gl.glGetDoublev(GL2.GL_PROJECTION_MATRIX, projection, 0);
    gl.glGetIntegerv(GL2.GL_VIEWPORT, viewport, 0);

    int vpheight = viewport[3];

    int wx = x;
    int wy = vpheight - y;

    GLU.createGLU(gl).gluUnProject(wx, wy, 0.0,
            modelview, 0,
            projection, 0,
            viewport, 0,
            rayStartPos, 0);
    GLU.createGLU(gl).gluUnProject(wx, wy, 1.0,
            modelview, 0,
            projection, 0,
            viewport, 0,
            rayEndPos, 0);

    mouseRayStart = new Vector3(rayStartPos[0], rayStartPos[1], rayStartPos[2]);
    mouseRayEnd = new Vector3(rayEndPos[0], rayEndPos[1], rayEndPos[2]);
}