Bilateral Propagation Network for Depth Completion
Authors: Jie Tang, Fei-Peng Tian, Boshi An, Jian Li, Ping Tan

Depth completion aims to derive a dense depth map from sparse depth measurements with a synchronized color image. Current state-of-the-art (SOTA) methods are predominantly propagation-based which work as an iterative refinement on the initial estimated dense depth. However the initial depth estimations mostly result from direct applications of convolutional layers on the sparse depth map. In this paper we present a Bilateral Propagation Network (BP-Net) that propagates depth at the earliest stage to avoid directly convolving on sparse data. Specifically our approach propagates the target depth from nearby depth measurements via a non-linear model whose coefficients are generated through a multi-layer perceptron conditioned on both radiometric difference and spatial distance. By integrating bilateral propagation with multi-modal fusion and depth refinement in a multi-scale framework our BP-Net demonstrates outstanding performance on both indoor and outdoor scenes. It achieves SOTA on the NYUv2 dataset and ranks 1st on the KITTI depth completion benchmark at the time of submission. Experimental results not only show the effectiveness of bilateral propagation but also emphasize the significance of early-stage propagation in contrast to the refinement stage. Our code and trained models will be available on the project page.