Visualization: Difference between revisions

4. Start ParaView on your laptop, go to ''File -> Connect'' (or click on the green ''Connect'' button on the toolbar) and click ''Add Server''. You will need to point ParaView to your local port 11111, so you can do something like name = cedar, server type = Client/Server, host = localhost, port = 11111, then click ''Configure'', select ''Manual'' and click ''Save''.

'''NOTE:''' An important setting in ParaView's preferences is ''Render View -> Remote/Parallel Rendering Options -> Remote Render Threshold''. If you set it to default (20MB) or similar, small rendering will be done on your laptop's GPU, the rotation with a mouse will be fast, but anything modestly intensive (under 20MB) will be shipped to your laptop and—depending on your connection—visualization might be slow. If you set it to 0MB, all rendering will be remote including rotation, so you will be really using the cluster's GPU for everything, which is good for large data processing but not so good for interactivity. Experiment with the threshold to find a suitable value.

You can also do interactive client-server ParaView rendering on cluster CPUs. For some types of rendering, modern CPU-based libraries such as OSPRay and OpenSWR offer performance quite similar to GPU-based rendering. Also, since the ParaView server uses MPI for distributed-memory processing, for very large datasets one can do parallel rendering on a large number of CPU cores, either on a single node, or scattered across multiple nodes.

1. First, install on your laptop the same ParaView version as the one available on the cluster you will be using; log into Cedar or Graham and start a serial GPU interactive job.

The job should automatically start on one of the CPU interactive nodes.

2. At the prompt that is now running inside your job, load the offscreen ParaView module and start the server.

The '''--mesa-swr-avx2''' flag is important for much faster software rendering with the OpenSWR library.  

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3. Make a note of the node (in this case cdr774) and the port (usually 11111) and in another terminal on your laptop (on Mac/Linux; in Windows use a terminal emulator) link the port 11111 on your laptop and the same port on the compute node (make sure to use the correct compute node).

4. Start ParaView on your laptop, go to ''File -> Connect'' (or click on the green ''Connect'' button in the toolbar) and click ''Add Server''. You will need to point ParaView to your local port 11111, so you can do something like name = cedar, server type = Client/Server, host = localhost, port = 11111, then click ''Configure'', select ''Manual'' and click ''Save''.

:Once the remote is added to the configuration, simply select the server from the list and click ''Connect''. The first terminal window that read ''Accepting connection ...'' will now read ''Client connected''.

5. Open a file in ParaView (it will point you to the remote filesystem) and visualize it as usual.

 

'''NOTE:''' An important setting in ParaView's preferences is ''Render View -> Remote/Parallel Rendering Options -> Remote Render Threshold''. If you set it to default (20MB) or similar, small rendering will be done on your laptop's GPU, the rotation with a mouse will be fast, but anything modestly intensive (under 20MB) will be shipped to your laptop and—depending on your connection—visualization might be slow. If you set it to 0MB, all rendering will be remote including rotation, so you will be really using the cluster's GPU for everything, which is good for large data processing but not so good for interactivity. Experiment with the threshold to find a suitable value.

If you want to do parallel rendering on multiple CPUs, start a parallel job; don't forget to specify the correct maximum walltime limit.

You can launch a new cloud virtual machine (VM) as described in the [[Cloud Quick Start|Cloud Quick Start Guide]]. Once you log into the VM, you will need to install some additional packages to be able to compile ParaView or VisIt. For example, on a CentOS VM you can type:

Since the VM does not have access to a GPU (most Cloud West VMs don't), we need to compile ParaView with OSMesa support so that it can do offscreen (software) rendering. The default configuration of OSMesa will enable OpenSWR (Intel's software rasterization library to run OpenGL). What you will end up with is a ParaView server that uses OSMesa for offscreen CPU-based rendering without X but with both llvmpipe (older and slower) and SWR (newer and faster) drivers built. We recommend using SWR.