Next: VRML Scene graph Up: Implementation Issues Previous: Implementation Issues

Network Communication

If the client requests an iso-surface for a given iso-value and resolution level, the server computes the iso-surface and sends the resulting triangles to the client. The server sends further information in order to mark the triangles for building the hierarchy of surface levels. The client-server communication is based on Berkeley sockets.

A simple protocol was defined, which consists of four client-server and three server-client commands:

• Client-Server commands
  • Load_Dataset Loads a volume dataset onto the server.
  • Compute_Isosurface Computes an iso-surface from level 0 to a given end level.
  • Refine_Isosurface Refines an iso-surface from a start level to a given end level.
  • Close_Connection Asks the server to close the socket connection.
• Server-Client commands
  • Sending_Maximum_Level Tells the client the maximum level, up to which the iso-surface can be refined.
  • Sending_Isosurface Sends an iso-surface from level 0 up to the requested end level.
  • Refining_Isosurface Refines an iso-surface from the requested level to the end level.

The client application first requests the server to load a dataset (Load_Dataset). The server loads the dataset and returns the maximum level of resolution up to which the iso-surface can be refined (Sending_Maximum_Level). An iso-surface can be requested by the client applet for a given dataset, an iso-value and a level of detail (Compute_Isosurface). The server responds with the command Sending_Isosurface, which is followed by the iso-surface data up to the requested level.

If a higher resolution is requested by the user, the client sends the command Refine_Isosurface, and the server refines the iso-surface. The server responds with the command Refining_Isosurface and sends the corresponding surface levels. Since only parts of the iso-surface change from one level to another, the server sends the new triangles refining the surface. The non-refined parts of the iso-surface are reused at the next level.