目的 目前互联网上构建的虚拟世界规模越来越大,但在现实网络带宽有限的情况下,实时传输海量复杂虚拟场景一直都是难以解决的“瓶颈问题”,针对该极具挑战性的问题进行了综述性研究。方法 首先对大规模3维虚拟场景传输的主要技术进行了概述,然后分别对其中的关键技术如大规模虚拟场景的轻量化与流式化技术、P2P-Cloud(Peer to Peer-Cloud)网络架构、资源发现/邻居发现策略、不同网络架构的虚拟场景数据分发策略和移动网络场景传输等进行了详细综述。结果 阐明了虚拟场景传输主要技术之间的关系,并通过对已有经典成果的对比,分析了它们的优缺点及需要解决的关键问题。结论 分别从虚拟场景传输的场景预处理、基于云的混合网络架构和移动网络中的场景传输这3个发展方向做了前瞻性的展望。

Objective Recent studies have developed virtual environment technologies based on peet-to-peer(P2P) networking. Some articles have reviewed these technologies from different aspects. However, analysis from the aspect of scene data transmission remains lacking. To date, an increasing number of scholars are beginning to investigate scene data transmission. Therefore, a survey of virtual scene transmission works based on P2P networking is indispensable.Method A summary research on this challenging issue was performed, and existing achievements from diverse aspects were analyzed. The transmission technologies of large-scale 3D virtual scenes were outlined. Lightweight modeling and streaming technologies for large-scale virtual scene, virtual environment network architecture, interest management, resource/neighbor discovery mechanism, scene data delivery strategies of different network architecture, cache update mechanism, and data perfecting mechanism were proposed for virtual environment transmission. These technologies were reviewed and compared, and their relationships were determined.Result A significant number of similar objects and model elements exist in a large-scale virtual scene. Thus, reusing repeated components can significantly reduce the amount of scene data. Concerning the lightweight works of 3D models, this study discusses the proposition and improvement of a model lightweight method and a new voxel unit-matching method. The advantages and disadvantages of symmetry methods for singly connected models were analyzed, and the proposition and definition of model streaming technologies were introduced. Several streaming methods and data structure of the base/incremental mesh were also expounded. The maturity of cloud computation depends on its flexible contraction, powerful performance, stable bandwidth, and cost-effective characteristics. Thus, an increasing number of distributed virtual environments were deployed for Cloud service, particularly in massively multiplayer online games applications. Combining P2P networking with cloud computing, we deployed the super-node on the cloud to maximize the stability of Cloud and the scalability of P2P. Such properties can enhance the stability and load balance of the entire driver vision enhancement (DVE) system. Currently, studies on P2P-Cloud only focused on using Cloud to improve DVE data delivery, load balancing, and QoS. Studies that adopt P2P-Cloud architecture and analyze its infrastructure, deployment principle, and cost should be expounded.In the structured DVE, the nodes undergo a resource discovery mechanism to search the desired scene data. Dihydrotestosterone (DHT) is usually used to accurately locate the requested data of the nodes. Therefore, in the structural network, sending a considerable number of requests to locate the resource is not needed with a low network latency and overhead. However, when the nodes frequently join and leave the system, churn can easily occur and cause maintenance difficulty. Classic mechanisms such as SimMud, Colyseus, and PBT were described and compared in terms of advantages and disadvantages. The resources in the unstructured DVE do not necessarily have a relationship to the locations or have a global mechanism similar to DHT to manage the connections, movements, and exits of the nodes. The nodes were used to detect nearby neighbors depending on a mutual notification system. They also send updated information to their neighbors. The neighbor discovery mechanisms pSense and VON were used to illustrate this principle.A data-distributed strategy can expound the mechanism for dividing the labor between nodes to achieve efficient and real-time transmission of the scene data. A comparative review was conducted using pull/push strategy, publish/subscribe mechanism, unicast, and multicast. Several classic DVE systems with P2P architecture were analyzed from the aspects of topological architecture, resource/neighbor discovery mechanism, and data-distributed strategy. The demand of users for online virtual scene roaming has increased with the improved intelligence, power, and popularity of mobile terminals, process ability, and 3G/WiFi, respectively. Package loss would seriously affect mobile devices when receiving virtual scene data because of the limited bandwidth and unstable link of mobile networks. To overcome this problem, this study introduces strategies for lost packet recovery and rate control.Conclusions This study proposes the transmission of large-scale virtual scenes on mobile networks using scene lightweight pretreatment and P2P-Cloud hybrid architecture.