Context-Aware Multi-view Stereo Network for Efficient Edge-Preserving Depth Estimation

Learning-based multi-view stereo methods have achieved great progress in recent years by employing the coarse-to-fine depth estimation framework. However, existing methods still encounter difficulties in recovering depth in featureless areas, object boundaries, and thin structures which mainly due to the poor distinguishability of matching clues in low-textured regions, the inherently smooth properties of 3D convolution neural networks used for cost volume regularization, and information loss of the coarsest scale features. To address these issues, we propose a Context-Aware multi-view stereo Network (CANet) that leverages contextual cues in images to achieve efficient edge-preserving depth estimation. The structural self-similarity information in the reference view is exploited by the introduced self-similarity attended cost aggregation module to perform long-range dependencies modeling in the cost volume, which can boost the matchability of featureless regions. The context information in the reference view is subsequently utilized to progressively refine multi-scale depth estimation through the proposed hierarchical edge-preserving residual learning module, resulting in delicate depth estimation at edges. To enrich features at the coarsest scale by making it focus more on delicate areas, a focal selection module is presented which can enhance the recovery of initial depth with finer details such as thin structure. By integrating the strategies above into the well-designed lightweight cascade framework, CANet achieves superior performance and efficiency trade-offs. Extensive experiments show that the proposed method achieves state-of-the-art performance with fast inference speed and low memory usage. Notably, CANet ranks first on challenging Tanks and Temples advanced dataset and ETH3D high-res benchmark among all published learning-based methods.