[visit-users] Local rendering, and how do I know it's using the graphics card? (and other silly questions)

Burlen Loring burlen.loring at gmail.com
Thu Jul 10 12:40:16 EDT 2014


Don't disagree with you, but on the ParaView comment: My experience is 
that GPU's can be significantly faster, with the caveat that it's 
depends on: rendering algorithm in use, on the number of processes 
sharing the GPU, and screen size and vertex count. Obviously if you have 
16 processes hitting the same GPU it can be a problem. In those 
situations CPU is a better choice. Here are some benchmarks 
<http://www.paraview.org/Wiki/ParaView_And_Mesa_3D#A_comparison_of_OSMesa_Gallium_llvmpipe.2C_OSMesa_classic_and.2C_GPU_Accelerated_Rendering_Performance> 
made recently using VTK comparing GPU to recent OSMesa. You can see that 
GPU offers big speed up in some cases and not so much in others. Note 
the red bars show the OSMesa classic which is what VisIt is currently 
using if you build with build_visit.

One potential advantage of having GPU's is that in ParaView and VTK this 
enables more rendering techniques. OSMesa especially the older versions 
is quite limited in capabilities it provides.

Actually I'm curious if using the GPU enables more features in VisIt?


On 07/10/2014 08:08 AM, Brugger, Eric wrote:
> Paul,
>
> There is a distributed GPU-based rendering in VisIt, we just don't generally recommend it. It may be tricky to set up and it generally doesn't improve performance. When running in parallel the amount of geometry to render per process is fairly small and modern CPUs can render small amounts of geometry very quickly and you don't have the cost of doing the frame buffer readback. The rendering rate is usually limited by the compositing, which requires shipping frame buffer fragments over the interconnect. I have heard of similar experiences from ParaView users at Sandia.
>
> Eric
>
> -----Original Message-----
> From: Paul Melis [mailto:paul.melis at surfsara.nl]
> Sent: Thursday, July 10, 2014 12:32 AM
> To: VisIt software users community
> Subject: Re: [visit-users] Local rendering, and how do I know it's using the graphics card? (and other silly questions)
>
> Hi Eric,
>
> On 09-07-14 17:18, Brugger, Eric wrote:
>> If you are running completely locally you should be
>   > using the graphics card. You can change the rendering  > options with the "Rendering" window, which can be  > brought up by going to "Options->Rendering".
>   > You would need to go to the "Advanced" tab and  > change "Use scalable rendering" to "Always" to force  > it to always render in software. If you changed it to  > "Never" then it would always use the graphics card.
>
> I happened to be following this thread, a question: the above seems to imply that scalable rendering is always rendering in software (i.e. not using GPUs). Is that really true? Is there no distributed GPU-based rendering in VisIt like ParaView provides?
>
> Regards,
> Paul
>
> --
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>
> Paul Melis
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