基于虛擬現(xiàn)實(shí)的虛擬實(shí)驗(yàn)室外文翻譯-文庫(kù)吧資料
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【正文】 sers while moving in 3D space, represents other users by avatars,and allows, in a teaching environment, to assure that all participants see what a special user () considers relevant. An important issue on supporting people in teaching and discussion is the ease of use. So we have taken a great effort to provide even the novice the user with maximum fort in all stages of user its support of OpenGL and XGL in bination with the use of the MBP (MRT Binary Protocol for the transport of application specific data),external simulations can also use MRTVR as a specialized display server.In bination with other MBoneTools such as VIC (video), VAT (audio) or Whiteboard (paper), MRTVR implements distributed interaction with VRML scenes. Figure 5 shows the integration of MRTVR in the SDRTool, which allows to use MRTVR in bination with other tools handling video, audio, whitoboard and text.MRTVR is not restricted to the visualisation of other participants through avatars or selection of objects (picking).MRTVR also allows the modification of the scene description, including avatars, camera postions or the state of the MRTVR viewer through external programs or other MRTVR’ even allows a modification or customization of the supported mand set.3. DesignThe design of MRTVR consists of three main distinguish between data transport, data replication and visualisation. Data transport realizes the transportation of messages by different protocols or media between MRTVR’s. Data replication assures the consistency of sceneDatabases, while the visualisation assures a fast,multiplatform,multiquality display of the virtual environment. Data TransportDataTransport is implemented as a collection of different datatransport classes. These classes realize connections between each other using different protocolls like TCX, UDP or MBone. The modification of the scene database is done by a set of messages, which are sent to the different MRTVR’s using the datatransport classes. These messages encode the operations which should be executed by the different programs. To implement distributed environments, messages have to be passed to every participant, resulting in an exponential growth of messages. Even a small number of participants may cause problems when using one ore more transmission of a huge amount of data to a large number of participants thereby assuring that important packages are reliably transmitted is a highly challenging goal. By separating the messages into important and unimportant ones we can easily see that a few important messages are outnumbered by far by the unimportant ones. Important messages deal with geometric object such as locking, inserting or deleting objects. Changes of viewpoints are less important but very frequent.Examples:l A distributed presentation consist of a data transmission phase at the beginning followed by mostly viewpoint changes and picking tasks for the rest of the session.l A distributed simulation (robotic experiment) consist af a data transmission phase at the beginning and many viewpoint changes. Packet loss during the robot movement is justifiable.l A distributed multiuser editing environment needs a data transmission phase at the beginning and severa1 object modification events while editing. Information loss is not acceptable. Updates only concern one object at a time, resulting in low data rates using secure transmission.At this time MRTVR uses MBone transmission for all package types. Ongoing work will use a CORBAbased implementation for the safe transmission of important packages and MBone for less important messages. Figure 2. MRTVR DataTransport,with different Transport Modules ReplicationData replication between connected MRTVR’s is managed by the data replication mechanism. Messages control the creation of new objects and the modification or deletion of existing objects. Users joining a session a
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