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IMAGE-BASED WALKTHROUGH OVER THE INTERNET

In this paper, we describe a client-server image-based walkthrough system. This system employs pictures, panoramas, and concentric mosaics captured from real scenes. These data are compressed and stored in a remote server, and can be retrieved over the Internet. Rather than transmitting a video sequence frame by frame, our system at the client end allows users to selectively retrieve image segments at specific viewpoints and viewing directions. This selective retrieval is achieved by implementing a client-server communication protocol. Cache strategies are designed to ensure a smooth viewing experience for the users. Experiments show that within a local area network, our system can reach over 15 frames per second (fps) with a resolution of 360×288 pixels while the user is rotating and 3 fps while the user is translating. Even with a 56Kbps modem, our system can still reach over 15 fps with a resolution of 180×144 pixels for rotation and 1 fps for translation. With partial cache scheme, our system uses no more than 1MB of RAM at the client end. Therefore our system is particularly suitable for online virtual tours, shopping, and communication on hand-held, palm-size PCs or mobile phones.