Enabling VR Juggler's performance monitoring capabilities requires two simple additions to the application's configuration file.
First, we need to tell the application which kinds of performance data to gather. Various components of VR Juggler create data buffers for collecting performance data, and each of these buffers can be turned on or off. The buffers are identified by their name (e.g. "Kernel" or "Head Latency"). Additionally, application code can create its own data buffers with unique names.
These categories can be individually activated and deactivated with a Performance Measurements ConfigChunk (which you can create under the Environment Manager folder in VjControl's config file editing window) - see Figure 4.1. Simply create an entry with the buffer's name and set it to true or false. If a buffer isn't named in the configuration, it defaults to false (disabled).
Sometimes, VR Juggler will create multiple buffers with similar names. For example, if there are two drawing threads, it will create buffers called "vjGlPipe 1" and "vjGlPipe 2". You can turn on the performance tests in both buffers by using the common prefix "vjGlPipe" in the configuration file.
Secondly, we must tell VR Juggler where to send the performance data once it is collected. This is determined by the Performance Target property in the Environment Manager ConfigChunk. If we are dynamically reconfiguring VR Juggler so that we can view performance while the application is running, the pulldown menu for the Performance Target property will list the network connection between VjControl and the application as a possible target. If that connection is selected, performance data can be viewed in a panel in VjControl (click on the Performance tab).
We can also send performance data to a file for later evaluation. To do this, first create an EM Connection ConfigChunk (found in the Environment Manager folder in VjControl). This chunk is illustrated in Figure 4.2. Here we can select the name of the output file and tell VR Juggler to "activate" it - that is, to open it and write to it. Note that the File Mode property should always be "output" for a log file.
Once we have created the EM Connection for our log file, we can return to the Environment Manager ConfigChunk and select it as our target for performance data. The output file that results from running the application with this configuration can be loaded into VjControl's Performance panel for analysis.
