ANSYS issues on 2.2.6

[Łukasz Flis]

Dear  TurboVNC-Users

After upgrading TurboVNC from version 2.1.x to 2.2.6 ansys workbench stopped working properly. We have tested various variants (with +iglx / -iglx, with mesa llvmpipe rendering and also with vglrun with Tesla V100)

Symptoms: blank startup splash screen, blank applcation window (screen attached)

Upgrading from 2.0 or 2.1 to 2.2.x on the other hand fixes problem with CFD-post application (Qt5) by providing glx extension in TurboVNC server itself (in Ansys CFD  QT5 is built with xcb_glx integration only thus requires X with GLX)

Questions:

* are you aware of any configuration (distro, settings) for TurboVNC 2.2 and Ansys 2020 that is working properly ?

* i ran out of ideas how do debug it - do you have any  hints how to approach debugging such issues?

Best Regards

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Lukasz Flis

[DRC]

I haven't heard of any issues, but here are a few ideas:

1. Try to start the TurboVNC Server without the X Composite extension, by passing '-extension Composite' to /opt/TurboVNC/bin/vncserver.  That has proven necessary with certain "unique" (<cough> broken <cough>) applications and window managers, although typically the applications/WMs that require this are quite old-- like so old that they probably wouldn't work correctly with any modern X server.

2. Try disabling the GLX extension, by passing '-extension GLX' to /opt/TurboVNC/bin/vncserver.  It could be that the same thing that is making CFD work is also breaking Workbench.  Note that ANSYS CFD should not require a GLX extension if VirtualGL is being used.  If it does in fact require a GLX extension, even when using VGL, then that's either a bug in VirtualGL, or the application is doing something really "unique" (see above) that we'll have to work around using an application recipe.  Let's just say that there is precedent for that:  https://github.com/VirtualGL/virtualgl/blob/master/doc/apprecipes.txt#L111-L117.  If nothing else, this exercise will at least narrow down what caused Workbench to break in TurboVNC 2.2.x.

3. Set VGL_LOGO=1 in the environment prior to launching ANSYS Workbench using vglrun.  That will verify whether VirtualGL is even being used.  If Workbench doesn't get far enough to actually display anything with OpenGL, then you might also try enabling tracing ('vglrun +tr') and look at whether OpenGL and GLX functions are actually being intercepted from the application.

The reason I'm suggesting #2 and #3 is that certain ANSYS applications (Fluent, for instance) automatically disable OpenGL rendering if they detect a remote display environment, and you have to use application-specific environment variables to override that behavior.  Workbench has never been known to require that, however.

I'm happy to look into this issue in more detail if your organization is willing to pay for my labor, but absent that, there is little else I can do.  As an independent contractor, I have no access to commercial 3D applications.

DRC

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