Real-time three-dimensional (3D) scene representations serve as one of the building blocks that bolster various innovative applications, e.g., digital manufacturing, Virtual/Augmented/Extended/Mixed Reality (VR/AR/XR/MR), and the metaverse. Despite substantial efforts that have been made to real-time communications and computing, real-time 3D scene representations remain a challenging task. This paper investigates the tradeoff between timeliness and fidelity in real-time 3D scene representations. Specifically, we establish a framework to evaluate the impact of communication delay on the tradeoff, where the real-world scenario is monitored by multiple cameras that communicate with an edge server. To improve fidelity for 3D scene representations, we propose to use a single-step Proximal Policy Optimization (PPO) method that leverages the Age of Information (AoI) to decide if the received image needs to be involved in 3D scene representations and rendering. We test our framework and the proposed approach with different well-known 3D scene representation methods. Simulation results reveal that real-time 3D scene representation can be sensitively affected by communication delay, and our proposed method can achieve optimal 3D scene representation results.

翻译：实时三维场景表示作为支撑各类创新应用（如数字化制造、虚拟/增强/扩展/混合现实以及元宇宙）的基础构件之一，尽管在实时通信与计算领域已付出大量努力，实现实时三维场景表示仍是一项具有挑战性的任务。本文研究实时三维场景表示中时效性与保真度之间的权衡关系。具体而言，我们建立了一个评估通信延迟对该权衡影响的理论框架，该框架中现实场景由多台摄像机监控，并与边缘服务器进行通信。为提升三维场景表示的保真度，我们提出采用单步近端策略优化方法，该方法利用信息年龄指标决策接收到的图像是否需要参与三维场景构建与渲染过程。我们通过多种经典三维场景表示方法对框架及所提方案进行测试。仿真结果表明，实时三维场景表示性能对通信延迟具有敏感性，且所提方法能够实现最优的三维场景表示效果。