View source for Rendering without display

==Introduction==
Rendering images on a remote HPC is slightly different from rendering images on your local computer, because the compute nodes in Euler don't have a display attached. The most suitable solution for  is, when the software itself provides offscreen rendering, but it can also be done using a virtual frame buffer.

==Offscreen rendering with OSMesa or EGL==
Please find below some links that provide information about how to use OSMesa or EGL for offscreen rendering:

 https://docs.mesa3d.org/osmesa.html
 https://blog.kitware.com/off-screen-rendering-through-the-native-platform-interface-egl/

==Virtual frame buffer==
Xvfb is a virtual framebuffer that is part of the X11 libraries. It is installed on Euler as a part of the operating system. By prefixing the command with <tt>xvfb-run -a</tt> the rendering is done in a frame buffer:
 
 sbatch [Slurm options] --wrap="xvfb-run -a my_command_that_does_the_rendering"

Please find below the available options for xvfb-run:

 [sfux@eu-login-33 ~]$ xvfb-run --help
 Usage: xvfb-run [OPTION ...] COMMAND
 Run COMMAND (usually an X client) in a virtual X server environment.
 Options:
 -a        --auto-servernum          try to get a free server number, starting at
                                     --server-num (deprecated, use --auto-display
                                     instead)
 -d        --auto-display            use the X server to find a display number
                                     automatically
 -e FILE   --error-file=FILE         file used to store xauth errors and Xvfb
                                     output (default: /dev/null)
 -f FILE   --auth-file=FILE          file used to store auth cookie
                                     (default: ./.Xauthority)
 -h        --help                    display this usage message and exit
 -n NUM    --server-num=NUM          server number to use (default: 99)
 -l        --listen-tcp              enable TCP port listening in the X server
 -p PROTO  --xauth-protocol=PROTO    X authority protocol name to use
                                     (default: xauth command's default)
 -s ARGS   --server-args=ARGS        arguments (other than server number and
                                     "-nolisten tcp") to pass to the Xvfb server
                                     (default: "-screen 0 640x480x8")
 -w DELAY  --wait=DELAY              delay in seconds to wait for Xvfb to start
                                     before running COMMAND (default: 3)
 [sfux@eu-login-33 ~]$