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maxime May 9, 2007 04:11

hello, I have installed OpenF
I have installed OpenFOAM all is ok.
I use VNC for remoting my linux cluster
But when I run the cavity tutorial, I have a problem as I start paraFoam.
I got the following message:
Xlib: extension "GLX" missing on display ":4.0"
the 4.0 gave me the intuition that the problem comes from VNC.
So I started parafoam direct from linux (no VNC) and I don't have the error emssage anymore.
The question is: what should be done for remoting paramfoam from VNC?
(FoamX works perfectly from VNC)

mplongjr May 9, 2007 11:53

When you use VNC, you are actu
When you use VNC, you are actually viewing your remote X session.. i.e. the X client and server are both on your cluster node..

When you start parafoam from an ssh/rsh session (with X11 forwarding) the X client is your local machine, so it has all of the available X extensions like GLX... VNC effectively bypasses your local X client, defeating the purpose of X..

to fix it, you either need to configure X with GLX on your remote node, or always use your local machine as the X client (log into your cluster with 'ssh -X {cluster-name}' .. or ssh -Y if your local machine has hardware accelerated graphics)

This is getting to be a pretty long reply, but I've been through this a lot and I know that it can be frustrating..

If you're running under Linux and you have direct rendering enabled on your local machine, you'll see much better performance in paraview (or any OpenGL application for that matter) if you run the application directly on your local machine instead of piping the X connection from the cluster..

osn May 10, 2007 00:10

That is your VNC's issue. T
That is your VNC's issue.

There is no problem with SUSE Linux's vncserver.
Or rebuild your vncserver with "#define BuildGlxExt YES".

(Of course its performance is not better than direct X session, but it is acceptable for me and I usually use OpenFOAM with vnc.)

maxime May 10, 2007 04:22

hi, thanx for your reply. I a
hi, thanx for your reply.
I am using SUSE Linxu Enterprise Server 9.
Tell in which file should I insert the #define BouilGlxExt Yes" line?

eugene May 10, 2007 05:38

I strongly recommend that you
I strongly recommend that you try freenx instead of the base VNC server/client. It is simply better for remote desktops.

mplongjr May 10, 2007 12:29

I'm not familiar with freenx..
I'm not familiar with freenx... does it support hardware accelerated OpenGL over a network connection? From my (very possibly flawed) understanding of X11, the only way to get direct graphics hardware access is to run the application (paraview) on the local machine using direct rendering in X...

when I'm logged into our cluster head node via ssh:

[cfd_user@cluster-head ~]$ glxinfo|grep direct
direct rendering: No

on my local workstation:

[cfd_user@local ~]$ glxinfo|grep direct
direct rendering: Yes

If your local machine does not support direct rendering, then it doesn't make much of a difference, but on my workstation (P4 3.2ghz, Nvidia QuadroFX 3500) glxgears gives me about 500 fps with direct rendering off and about 14000 fps with direct rendering on... that's the difference between smooth interaction and a slide show in paraview!

I guess if you don't have direct access to your data on a local workstation then running paraview over ssh or a remote desktop is your only option.

mplongjr May 10, 2007 13:19

Actually.. now that I think ab
Actually.. now that I think about it, using a remote desktop viewer is probably the only real option since running paraview via ssh over a slow network would not work too well.

I think I was confused a little by the original question. I'm going to have to give freenx a try for when I'm working from home.

rbw May 10, 2007 14:05

Actually, I think there is a m
Actually, I think there is a much better way.
I think paraview works like Visit; they are distribute programs, a renderer that runs on your local workstation connects, using some kind of protocol, to (a) remote data server(s) (they are parallel programs so your data can reside on several remote computers). This uses tcp connections on other ports than the ssh one, so you'll have some firewall/tunneling magic to do, depending on you network. The graphics run at full speed since the renderer window has full access to the your workstation graphics hardware.

I don't know how well this would work over a slow connection, but I'm using it (with Visit, however) from a windows (bleargh!) laptop into a linux server over a pretty lossy wireless connection on my home network and it's much better than any other alternative I tried (all the ones mentioned above.)

mplongjr May 10, 2007 14:32

I'm sure you're right about th
I'm sure you're right about that... I'm still coming up to speed on paraview, but I know that it is designed to do just what you say, allowing you to visualize huge data sets on distributed hardware. Eventually I'd like to get that going on our cluster, but it's pretty far down on my to do list at the moment.

eugene May 11, 2007 06:02

Check out Paraview 3 beta, its
Check out Paraview 3 beta, its pretty impressive and the client-server thing is better supported via the GUI.

dayas2003 May 15, 2007 09:18

To use VNC, I think you must n
To use VNC, I think you must need a program sharing utility like Citrix server etc ..

- Dayananda

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