Adaptive depth estimation for pyramid multi-view stereo

In this paper, we propose a Multi-View Stereo (MVS) network which can perform efficient high-resolution depth estimation with low memory consumption. Classical learning-based MVS approaches typically construct 3D cost volumes to regress depth information, making the output resolution rather limited as the memory consumption grows cubically with the input resolution. Although recent approaches have made significant progress in scalability by introducing the coarse-to-fine fashion or sequential cost map regularization, the memory consumption still grows quadratically with input resolution and is not friendly for commodity GPU. Observing that the surfaces of most objects in real world are locally smooth, we assume that most of the depth hypotheses upsampled from a well-estimated depth map are accurate. Based on the assumption, we propose a pyramid MVS network based on the adaptive depth estimation, which gradually refines and upsamples the depth map to the desired resolution. Instead of estimating depth hypotheses for all pixels in the depth map, our method only performs prediction at adaptively selected locations, alleviating excessive computation on well-estimated positions. To estimate depth hypotheses for sparse selected locations, we propose the lightweight pixelwise depth estimation network, which can estimate depth value for each selected location independently. Experiments demonstrate that our method can generate results comparable with the state-of-the-art learning-based methods while reconstructing more geometric details and consuming less GPU memory. (c) 2021 Elsevier Ltd. All rights reserved.