  Learning 3D representation plays a critical role in masked autoencoder (MAE)
based pre-training methods for point cloud, including single-modal and
cross-modal based MAE. Specifically, although cross-modal MAE methods learn
strong 3D representations via the auxiliary of other modal knowledge, they
often suffer from heavy computational burdens and heavily rely on massive
cross-modal data pairs that are often unavailable, which hinders their
applications in practice. Instead, single-modal methods with solely point
clouds as input are preferred in real applications due to their simplicity and
efficiency. However, such methods easily suffer from limited 3D representations
with global random mask input. To learn compact 3D representations, we propose
a simple yet effective Point Feature Enhancement Masked Autoencoders
(Point-FEMAE), which mainly consists of a global branch and a local branch to
capture latent semantic features. Specifically, to learn more compact features,
a share-parameter Transformer encoder is introduced to extract point features
from the global and local unmasked patches obtained by global random and local
block mask strategies, followed by a specific decoder to reconstruct.
Meanwhile, to further enhance features in the local branch, we propose a Local
Enhancement Module with local patch convolution to perceive fine-grained local
context at larger scales. Our method significantly improves the pre-training
efficiency compared to cross-modal alternatives, and extensive downstream
experiments underscore the state-of-the-art effectiveness, particularly
outperforming our baseline (Point-MAE) by 5.16%, 5.00%, and 5.04% in three
variants of ScanObjectNN, respectively. The code is available at
https://github.com/zyh16143998882/AAAI24-PointFEMAE.
