DIVE Record Replay

Overview | Basic Record | Basic Replay | Misc.

Overview

DIVE currently supports a crude version of record and replay. Essentially the record and replay tool acts as a 3rd party in a DIVE session. In record mode it saves all events to a file. In play mode it creates a world and pushes events in to it, without regard to existing participants. You can not interact with replays, and the replay tool must be allowed to create the world; that is the replay tool must be started before any viewing tools.

Getting the Demo

If you are at UCL a record and replay demo is currently copyable from our CVS repository. On cygwin the CVSROOT is //smbhelp/vr-dive/cvsroot and the package is record-replay. That is

export CVSROOT=//smbhelp/vr-dive/cvsroot
cvs checkout record-replay

If you aren't able to see the repository then you download a zipped version here: record-replay-demo.tgz.

You also need to use a recent bug-fixed version of DIVE (3.3x6 or later). If you are at UCL, find this in the UNIX directory

/cs/research/vr/dive/starship/dive

or, if you are on WinXX

\\smbhelp\vr-dive\dive

Notes

The record and replay tool is actually ONE executable recorder(.exe). On Unix, you will find there is a symbollic link in the appl directory from player to recorder. On Unix, the executable determines its own name to determine its behaviour (record or replay). This doesn't work on Win32, so there are also commandline switches (-record, -play) to force the behaviour to one or other mode.

Limitations

At the moment, replay is once through only. That is, you start the player, then start the viewers. The timing of events seems to be "buggy" in that although the code is there to time events as per the original event file, actually it replays faster or slower depending on the frame rate of the rendering. This limitation should go away soon.

Recording is quite flexible; you can start a recorder at any time. The first thing that recorder does is save the state of the whole world in a .bvr file, and then generates an event log with all subsequent event. The limitation is that output file naming is hard-coded (bvr file) or configure in the config file (event log). This means log maintenance is fiddly. This limitation will go away soon.

Note that it is very important that the diveserver uses exactly the same multicast groups for record and replay. See the notes about run_server below. This limitation will go away soon.

Read the README.txt file in the demo directory - it tells you how to avoid pain and embarrassment from overwriting your precious files. This is the top thing to fix.

Basic Record

Start a diveserver

For example run_server
Note that in that script, we reference a server.dat file. This file can be used to make sure that diveserver gives a world a very specific multicast group - this ensures that the replay tool will later be able to determine which group to send to. That files contains the line, where puzzle is the name of the world (the Rubik's puzzle in this example).
DIVE-3.3x puzzle 226.32.44.12 1166 4 multicast
Start your world
- For example run_desk
- Nothing to note here
Start the recorder
- For example run_recorder
- Note that you give it an existing directory to log files to, and also that the -record commandline variable.
- The output files will be out.bvr in the current directory and an eventlog which you specfied in the config file for the recorder. If objects were created during the session, you will see numerous other .bvr files numbered like s2a4..bvr, s2a4.1.nvr, etc.. There may be dozens, or hundreds of these files - they are all important.

Notes

The .bvr file and event log files are dependent on a major DIVE version such as DIVE3.3x. They should work with any minor variation on this branch (3.3x5, 3.3x6, etc.)

Basic Replay

Start a diveserver

For example run_server
Note we re-use the server.dat file. If you didn't use the same one when you recorded you will be unable to replay.
Start the player
- For example run_play
- Note that recorder will wait a fixed number of seconds before starting to replay. This can be overridden with -wait X on the command line where X is seconds as an integer.
Start a world viewer
- For example run_desk
- Note that if you don't see any avatars, but it appears to be working, then it may be because of subjective views. Try changing your subjective view login. This typically happens when you record a CAVE session, where the user's own avatar is subjectively invisible to herself, so if you replay logged in under the same account, you also don't see the avatar.

Misc.

To Do

Better file management
Remove multicast group specificity
Write a TCL UI to control recording and replaying
Variable speed replay
Online record and replay
Integrating other log files to replay
1st person replay

Anthony Steed, A.Steed@cs.ucl.ac.uk