[vtkusers] [vtk-developers] [vtk-users] OpenGL2 - GPU Volume Rendering performance

Tue Oct 27 09:43:05 EDT 2015

Hello Aashish,

Sorry for the late answer, I was busy this morning.
Thanks for testing with the DataSet.
I agree the performance is still quite good with the new backend, and I
also get something like 15/20 fps on windows on an HD screen. But when
compared to the old one, and in some condition (when zoomed especially), it
looks really slower to me
The two tested version are :
- ParaView 4.4.0 64 bits final version for the old backend
- ParaView 4.4.0-193-gec96423 64 bits, for the OpenGL2 backend.
on a windows 7 box, Xeon E3-1220 v3 CPU, 16GB ram and Nvidia Quadro K420

To highlight the difference, here is what I do :
- Launch both version on the same computer at the same time
- Load the above dataset on each
- Select volume rendering
- Adjust the transfer function data range to [100-750] (the default "Cool
to Warm" is fine)
- Set the view direction to +Y
- Adjust the Y of the camera position to -300

And start interacting ...
Dunno if there is an easy way to print out the Frame Rate in Paraview, but
the new version seems really twice slower in these conditions... We can see
it does not scale in the same way, the old backend seems more aggressive on
the image sample reduction, hence the interactivity is better.
Shading enable or not does not change much

I'm aware of the DesiredUpdateRate thing, we use to play with this with the
old backend to fine tune the interactivity, although what's really inside
was never clear to me

I hope that there is enough information for you to reproduce this, do not
hesitate to ask for some more information.

Thanks a lot for your help
Simon

2015-10-27 14:10 GMT+01:00 Aashish Chaudhary <aashish.chaudhary at kitware.com>
:

> Dear Simon,
>
> Checking again. Wondering if you can provide some more detail on the
> binary you are using and whether or not without shading the rendering
> performance comparable to older version.
>
> Thanks,
>
>
> On Mon, Oct 26, 2015 at 3:12 PM, Aashish Chaudhary <
> aashish.chaudhary at kitware.com> wrote:
>
>> Simon,
>>
>> I used your dataset on paraview master as of today on my Linux box
>> running Ubuntu 14.04 and NVIDA Quadro card and I am getting about 15-20 FPS
>> with shading on with 1920x1080 resolution.
>>
>> Are you on the proper 4.4 or using RC1/RC2? I checked the shading
>> performance fix was in 4.4 but not in RC's. I don't have access to Windows
>> box right away but I will try there too.
>>
>> NOTE: You might get multiple emails because of the attachment size issue.
>> Sorry about that.
>>
>> Thanks,
>>
>> On Mon, Oct 26, 2015 at 2:45 PM, Aashish Chaudhary <
>> aashish.chaudhary at kitware.com> wrote:
>>
>>>
>>>
>>> On Mon, Oct 26, 2015 at 2:13 PM, Simon ESNEAULT <
>>> simon.esneault at gmail.com> wrote:
>>>
>>>> Hello Aashish,
>>>>
>>>> Thanks for the quick answer
>>>> We are using a vtkImageData, 512x512x591 with short element (you can
>>>> find the dataset here :
>>>> https://www.dropbox.com/s/ptqwi0ebv75kt35/volume.zip). So I think it's
>>>> all about GPU volume raycast mapper.
>>>> The new mapper does bring low resolution, but when compared to the old
>>>> one, it seems less "low resolution" during interaction than the old one
>>>>
>>>
>>> Right, so that's why its not a exact comparison. What happens is that
>>> depending on what is interactive, (you can set the desired update rate in
>>> VTK, not exposed in ParaView I believe),  it will do interactive but with
>>> higher resolution (smaller sample distance).  If they both have the same
>>> sample distance, then the new mapper should out perform the old one,
>>> however, there is another thing we need to consider here which is shading.
>>>
>>>
>>>> Shading is enabled, gradient opacity disabled
>>>>
>>>
>>> Can you disable the shading and see if now they both (opengl1 and 2)
>>> equally better? We already pushed a fix for it but not sure if that you
>>> have in your build.
>>>
>>>>
>>>> Don't know if you need a minimal example, but I believe the
>>>> GPURenderDemo used with this dataset is enough to highlight the slow down.
>>>>
>>>
>>> Yes, I will use this dataset. Thanks.
>>>
>>>>
>>>> Thanks
>>>> Simon
>>>>
>>>>
>>>> 2015-10-26 18:57 GMT+01:00 Aashish Chaudhary <
>>>> aashish.chaudhary at kitware.com>:
>>>>
>>>>> Also,
>>>>>
>>>>> Do you have shading enabled? We fixed a bug with shading that was
>>>>> causing the slow performance a while back. I don't remember if that was
>>>>> included in 4.4 or not ( I can check ).
>>>>>
>>>>> - Aashish
>>>>>
>>>>> On Mon, Oct 26, 2015 at 1:53 PM, Aashish Chaudhary <
>>>>> aashish.chaudhary at kitware.com> wrote:
>>>>>
>>>>>> Simon,
>>>>>>
>>>>>> What kind of dataset you are using? Depending on the data type you
>>>>>> might be using
>>>>>> the GPU one or the unstructured renderer. The performance we measured
>>>>>> is related to the GPU ray cast mapper
>>>>>> and will apply only to the vtkImageData inputs.
>>>>>>
>>>>>> Also, helpful would be is if you can tell if the new mapper is
>>>>>> bringing low resolution when you interact with the volume (and whether or
>>>>>> not it happens with old mapper).
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>>
>>>>>> On Mon, Oct 26, 2015 at 1:47 PM, Simon ESNEAULT <
>>>>>> simon.esneault at gmail.com> wrote:
>>>>>>
>>>>>>> Hi All,
>>>>>>>
>>>>>>> We are trying to make the switch to the new OpenGL2 backend for our
>>>>>>> application, and although the switch was easy (thanks for not breaking the
>>>>>>> API ;) ), we can see a significant slowdown on the GPU volume rendering
>>>>>>> part, especially during interaction. Typically we dropped from 15/20 fps to
>>>>>>> 7/8 fps, on the same machine (Win32, Nvidia Quadro K420), with the same
>>>>>>> code around.
>>>>>>>
>>>>>>> This slow down can be seen in ParaView, if you compare the latest
>>>>>>> 4.4 OpenGL2 build with the classic 4.4 build while volume rendering a big
>>>>>>> enough volume (512^3)
>>>>>>>
>>>>>>> The blog post here
>>>>>>> http://www.kitware.com/blog/home/post/976
>>>>>>> claims that the new GPU volume rendering implementation should be
>>>>>>> faster than the old one, is there some more detailed explanation somewhere
>>>>>>> ? Are there some important parameters that can make the difference ?
>>>>>>>
>>>>>>> Thanks,
>>>>>>>
>>>>>>> Simon
>>>>>>>
>>>>>>> PS : The polygonal rendering seems a lot faster with the new backend
>>>>>>> !
>>>>>>>
>>>>>>> --
>>>>>>> ------------------------------------------------------------------
>>>>>>> Simon Esneault
>>>>>>> Rennes, France
>>>>>>> ------------------------------------------------------------------
>>>>>>>
>>>>>>> _______________________________________________
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>>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>>
>>>>>>
>>>>>>
>>>>>> *| Aashish Chaudhary | Technical Leader         | Kitware Inc.
>>>>>>     *
>>>>>> *| http://www.kitware.com/company/team/chaudhary.html
>>>>>> <http://www.kitware.com/company/team/chaudhary.html>*
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>>
>>>>>
>>>>>
>>>>> *| Aashish Chaudhary | Technical Leader         | Kitware Inc.
>>>>>     *
>>>>> *| http://www.kitware.com/company/team/chaudhary.html
>>>>> <http://www.kitware.com/company/team/chaudhary.html>*
>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> ------------------------------------------------------------------
>>>> Simon Esneault
>>>> Rennes, France
>>>> ------------------------------------------------------------------
>>>>
>>>
>>>
>>>
>>> --
>>>
>>>
>>>
>>> *| Aashish Chaudhary | Technical Leader         | Kitware Inc.
>>>   *
>>> *| http://www.kitware.com/company/team/chaudhary.html
>>> <http://www.kitware.com/company/team/chaudhary.html>*
>>>
>>
>>
>>
>> --
>>
>>
>>
>> *| Aashish Chaudhary | Technical Leader         | Kitware Inc.
>> *
>> *| http://www.kitware.com/company/team/chaudhary.html
>> <http://www.kitware.com/company/team/chaudhary.html>*
>>
>
>
>
> --
>
>
>
> *| Aashish Chaudhary | Technical Leader         | Kitware Inc.            *
> *| http://www.kitware.com/company/team/chaudhary.html
> <http://www.kitware.com/company/team/chaudhary.html>*
>

-- 
------------------------------------------------------------------
Simon Esneault
Rennes, France
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