private int index(Vector3d v) {

		Vector3d floor = v.floor();
		double x = floor.x();
		double y = floor.y();
		double z = floor.z();
		
		if (x == sx && y == sy && z == sz) {
			return -1;
		}

		if (size < epsilon) {
			return -1;
		}

		int index = 0;

		if (x > sx) {
			index |= X_FLAG;
		}

		if (y > sy) {
			index |= Y_FLAG;
		}

		if (z > sz) {
			index |= Z_FLAG;
		}

		return index;
	}