That is basically the difference. To use any implementation of OpenGL (which is what Mesa3D is), you first need an OpenGL context. On *nix you typically get this by opening a window with the Xhost. Even when doing offscreen rendering you need to get a context with the Xhost (because classically this was the interface to the graphics hardware).
Osmesa is a small library that sits on top of Mesa3D. It creates an OpenGL context without having to go to an Xhost. It has a different interface than GLX, so your software needs to specifically open an osmesa “window” in addition to linking to the correct library. As I recall, in order to use osmesa, you need to set VTK_OPENGL_HAS_OSMESA to ON and then set OSMESA_INCLUDE_DIR and OSMESA_LIBRARY. Typically the osmesa headers and libraries are in the same location as the Mesa 3D install. See this Wiki page for more info: http://www.paraview.org/Wiki/ParaView_And_Mesa_3D -Ken From: Walter Scott <[email protected]> Date: Monday, May 2, 2016 at 3:11 PM To: Kenneth Moreland <[email protected]>, "[email protected]" <[email protected]> Subject: RE: [Paraview] Cron job and ParaView OK, taking small steps here, what is OSMesa, and want is Mesa? Utkarsh and I had this discussion, but I never understood the difference. Having just googled the difference, If I understand correctly, OSMesa actually means Off Screen Mesa, and is compiled into Mesa. Otherwise, you get Mesa – software rendering, but into a GLX window? You are correct – I am not building OSMesa. Thus, my problem? Alan From: Moreland, Kenneth Sent: Monday, May 02, 2016 3:01 PM To: Scott, W Alan <[email protected]>; [email protected] Subject: Re: [Paraview] Cron job and ParaView Are you sure you are building with osmesa? Just using mesa is not sufficient. -Ken From: ParaView <[email protected]<mailto:[email protected]>> on behalf of Walter Scott <[email protected]<mailto:[email protected]>> Date: Monday, May 2, 2016 at 2:58 PM To: "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>> Subject: [EXTERNAL] [Paraview] Cron job and ParaView I have a user that is trying to run ParaView in a cron job, and keeps getting the following error on PV 4.4.0: 4.4.0/ParaView4/VTK/Rendering/OpenGL/vtkXOpenGLRenderWindow.cxx, line 542 vtkXOpenGLRenderWindow (0x5197850): bad X server connection Has anyone tried to do this, and figured out a solution? User has tried running a build I did – which attaches to Mesa – and has –use-offscreen-rendering turned on, and is running pvbatch. Same error. Any ideas? Thanks, Alan
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