Pri3D: Can 3D Priors Help 2D Representation Learning?
Ji Hou1     Saining Xie2     Benjamin Graham2     Angela Dai1     Matthias Nießner1    
    1Technical University of Munich     2Facebook AI Research
Proc. International Conference on Computer Vision (ICCV), IEEE, October 2021

Recent advances in 3D perception have shown impressive progress in understanding geometric structures of 3D shapes and even scenes. Inspired by these advances in geometric understanding, we aim to imbue image-based perception with representations learned under geometric constraints. We introduce an approach to learn view-invariant, geometry-aware representations for network pre-training, based on multi-view RGB-D data, that can then be effectively transferred to downstream 2D tasks. We propose to employ contrastive learning under both multi-view image constraints and image-geometry constraints to encode 3D priors into learned 2D representations. This results not only in improvement over 2D-only representation learning on the image-based tasks of semantic segmentation, instance segmentation, and object detection on real-world indoor datasets, but moreover, provides significant improvement in the low data regime. We show a significant improvement of 6.0% on semantic segmentation on full data as well as 11.9% on 20% data against our baselines on ScanNet.