“…Recently, some works (Liu et al, 2019a;Wang et al, 2021d;Puy et al, 2020;Li et al, 2021b,a;Wang et al, 2021a) have been done to realize supervised estimation of 3D scene flow from two consecutive frames of point clouds. However, just like it is difficult to obtain the ground truth of optical flow (Wang et al, 2021c(Wang et al, , 2020b, the ground truth of 3D scene flow is also difficult to obtain. Therefore, it is essential to perform unsupervised learning of 3D scene flow.…”