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

[Aashish Chaudhary]

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>*
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