== Using VirtualGL with the VGL Transport
[[PageOutline]]

http://www.virtualgl.org/vgldoc/2_2/#hd002

=== !Advantages/Disadvantages of the VGL Transport

==== Advantages
    * Every application window appears as a '''separate window''' on the user’s desktop.
    * consumes fewer server resources, since the 2D (X11) rendering occurs on the client machine
    * supports stereographic and overlay rendering

==== Disadvantages

    * The VGL Transport relies on the chatty remote X11 protocol. \\ As a result, the VGL Transport is '''not recommended''' for use on high-latency or low-bandwidth networks.
    * As with any remote X11 app, if the network connection drops, then the application '''will exit'''.


=== Using VirtualGL with the VGL Transport requires four general steps.
1. '''Install VirtualGL''' on your local machine.
2. '''Start an X Server''' on your local machine.
3. '''Connect to JURECAVIS''' with vglconnect -s.
4. '''Start the application''' with vglrun.

\\
=== 1. Install VirtualGL ...
Before you use can call '''vglconnect -s <userid>@jurecavis.fz-juelich.de''' you have to install VirtualGL on your local machine:
* Linux/MacOSX - http://www.virtualgl.org
* Windows+Cygwin - http://www.virtualgl.org/vgldoc/2_2/#hd004005
* Windows+Exceed - http://www.virtualgl.org/vgldoc/2_2/#hd004004
[http://www.virtualgl.org/vgldoc/2_2/#hd004/ | more ...]

\\
=== 2. Start an X Server ...
Start an X Server on your local machine. 
* Linux
  * your X11 server is used for your standard desktop and should be running already
* MacOSX
  * start the Mac X11 application
  * in the X11 application, start a new xterm [Command-N] if one isn’t already started
* Windows\Cygwin 
  * start Cygwin/X 
  * start a new xterm if one isn’t already started (right-click on the Cygwin/X taskbar icon, then select Applications–>xterm.) 

\\
=== 3. Connect to JURECAVIS ...
In this scenario any OpenGL commands are computed to a JPEG on JURECAVIS and send to the local machine via the VGL Transport Layer. The 2D (X11) command are directly passed to the local X server running on your machine.
By default the X11 traffic is encrypted, but the VGL Transport is left unencrypted to maximize performance.
This will fail on JURECA - you need to encrypt the VGL Transport, too, which is forced with the '''-s''' flag:

{{{ #!sh
vglconnect -s <USERID>@jurecavis.fz-juelich.de
}}}

[http://www.virtualgl.org/vgldoc/2_2/#hd007006 | more ...]

=== 4. Start the application ...
Now start your application on JURECA with '''vglrun''':
{{{ #!sh
vglrun <APP>
}}}

[http://www.virtualgl.org/vgldoc/2_2/#hd007 | more ...]


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any feedback welcomed - [mailto:h.zilken@fz.juelich.de], [mailto:j.goebbert@fz-juelich.de]