“…It is particularly important for 3D point cloud analysis, since the collection and annotation of point cloud data are much more expensive than 2D images. Popular SSL methods for point cloud include reconstruction [68,16,75,60,8,25,76,70,34,40,73,65,15], instance contrastive feature learning [49,51], consistency feature learning against augmentations [31], and other pretext tasks [52,43,1]. Among these methods, the masked auto-encoding [60,76,70,40] has been receiving more and more attention recently.…”