25.已知正方体ABCD−A1B1C1D1ABCD-A_{1}B_{1}C_{1}D_{1}ABCD−A1B1C1D1的棱长为3,动点PPP在△AB1CAB_{1}CAB1C内,满足D1P=14{D}_{1}P=\sqrt{14}D1P=14,则点PPP的轨迹长度为 ___2π\sqrt{2}\pi2π___.