Multi-resolution model transmission in distributed virtual environments

Distributed virtual environments allow users at different geographical locations to share and interact within a common virtual environment via a local network or through the Internet. To deliver a good performance for such applications, we need to address several issues in different research disciplines. First, we must be able to model virtual objects effectively. The recently developed multi-resolution techniques for object modeling are of great value here, since they are capable of simplifying the object models and therefore reducing the time to render them. This may greatly reduce the demand for rendering performance on the client machines. Second, with the constraint of the limited bandwidth of the Internet, we need to reduce the response time by reducing the amount of data requested over the network. Caching of suitable object models of high affinity will reduce the amount of data requested over the network for a faster response time. Prefetching object models by predicting those which are likely to be used in the near future and downloading them in advance will lead to a similar improvement. Third, the Internet often suffers from disconnection. A caching mechanism that allows objects to be cached with at least their minimum resolutions will be useful to provide at least a coarse view of the objects to the viewer for improved visual perception. In this paper, we describe our implementation of a distributed walkthrough system. Two techniques are fundamental to our system, a mu&-resolzltzon caching mechanism and a set of object prefetching mechanisms. Towards the end of the paper, we quantify the performance of t,he proposed mechanisms.

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