The VAROS Synthetic Underwater Data Set: Towards realistic multi-sensor underwater data with ground truth

Underwater visual perception requires being able to deal with bad and rapidly varying illumination and with reduced visibility due to water turbidity. The verification of such algorithms is crucial for safe and efficient underwater exploration and intervention operations. Ground truth data play an important role in evaluating vision algorithms. However, obtaining ground truth from real underwater environments is in general very hard, if possible at all. In a synthetic underwater 3D environment, however, (nearly) all parameters are known and controllable, and ground truth data can be absolutely accurate in terms of geometry. In this paper, we present the VAROS environment, our approach to generating highly realistic underwater video and auxiliary sensor data with precise ground truth, built around the Blender modeling and rendering environment. VAROS allows for physically realistic motion of the simulated underwater (UW) vehicle including moving illumination. Pose sequences are created by first defining way-points for the simulated underwater vehicle which are expanded into a smooth vehicle course sampled at IMU data rate (200Hz). This expansion uses a vehicle dynamics model and a discrete-time controller algorithm that simulates the sequential following of the way-points. The scenes are rendered using the raytracing method, which generates realistic images, integrating direct light, and indirect volumetric scattering. The VAROS dataset version 1 provides images, inertial measurement unit (IMU) and depth gauge data, as well as ground truth poses, depth images and surface normal images.水下视觉感知需要能够应对恶劣且快速变化的光照条件，以及因水体浊度导致的能见度下降问题。此类算法的验证对于安全高效的水下勘探与干预作业至关重要。真值数据（ground truth）在视觉算法的评估中发挥着关键作用。然而，即便能够从真实水下环境中获取真值数据，通常也极为困难。但在合成水下三维环境中，（几乎）所有参数均为已知且可控，其几何层面的真值数据可达到绝对精准。本文提出了VAROS环境——一种基于Blender建模与渲染环境构建的方法，可生成具备精准真值的高逼真度水下视频与辅助传感器数据。VAROS支持模拟水下（UW）载具的物理真实感运动，包括动态光照模拟。位姿序列的生成流程为：首先为模拟水下载具定义航点，随后将航点扩展为平滑的载具航行路径，并以惯性测量单元（Inertial Measurement Unit, IMU）的采样率（200Hz）进行采样。该扩展过程采用载具动力学模型与离散时间控制器算法，模拟载具按序追踪航点的过程。场景采用光线追踪方法进行渲染，通过整合直接光照与间接体积散射效果，生成逼真图像。VAROS数据集V1.0版本包含图像、惯性测量单元（IMU）与深度计数据，以及真值位姿、深度图像与表面法向量图像。