Abstract Stereo 3D reconstruction is continuously increasing its popularity in the study of mid-to small-scale sea waves. In the recent past, different approaches have been proposed to reconstruct the space-time sea surface elevation field from synchronized stereo frames. Usually, the reconstruction is performed by first recovering a dense and sparse 3D point cloud from stereo pairs and then by interpolating it into a regular grid. Even considering state-of-the-art methods, with typical image resolutions, it's unlikely to perform the first step in less than dozens of seconds (without paralellization), that can easily doubled if we include the subsequent interpolation step. This will limit the applicability of stereo based wave analysis for all the approaches (like monitoring or data assimilation) in which the time between the raw acquisition and the output of processed data is critical. In this paper, we propose a new method to directly estimate the sea surface spectrum over time from a sequence of stereo frames. We exploit the frequency dispersion relation of gravity waves and the (Non-uniform) Fast Fourier Transform to continuously update the 3D surface and 2D wavenumber spectrum estimations given a sparse set of matching features between the two frames. This effectively combines the two aforementioned steps with a performance gain of more than an order of magnitude while keeping a reconstruction accuracy that is extremely close to the current state-of-the-art approaches. Code is available at https://gitlab.com/fibe/wassfast .

中文翻译：

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海浪时空场的实时光学估计

摘要 立体 3D 重建在中小尺度海浪研究中越来越受欢迎。最近，已经提出了不同的方法来从同步立体帧重建时空海面高程场。通常，重建是通过首先从立体对中恢复密集和稀疏的 3D 点云，然后将其插入到规则网格中来执行的。即使考虑具有典型图像分辨率的最先进方法，也不太可能在不到几十秒的时间内执行第一步（没有并行化），如果我们包括后续的插值步骤，很容易加倍。这将限制基于立体声的波分析对所有方法（如监测或数据同化）的适用性，其中原始采集和处理数据输出之间的时间至关重要。在本文中，我们提出了一种新方法，可以从一系列立体帧中直接估计随时间变化的海面频谱。我们利用重力波的频率色散关系和（非均匀）快速傅立叶变换，在给定两帧之间的一组稀疏匹配特征的情况下，不断更新 3D 表面和 2D 波数谱估计。这有效地将上述两个步骤与超过一个数量级的性能增益相结合，同时保持非常接近当前最先进方法的重建精度。代码可在 https://gitlab 获得。