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camera motion blur possibly causing GPU render performance drop

Question asked by Helge Feddersen on Feb 22, 2018
Latest reply on Feb 23, 2018 by Helge Feddersen

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Hi All,

not sure if this is only on my system - hoping that maybe others could test this.

the issue i am having, in a nut shell, if i activate motion blur in the camera the GPU render performance drops big time

please see blow screenshots and dropbox link to a zip of the svpf file.

motion blur at the camera is currently deactivated.

would apreciate if members of the forum could test this

Helge

Dropbox link to svpj file (too big to attach in the post) 30MB

https://www.dropbox.com/s/mku90lqlnxi4otw/test.zip?dl=0

David Randle

Feb 22, 2018 9:12 PM

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Hi Helge - from what I remember, the majority of the "work" involved in rendering a scene with motion blur is in the translation of the geometry (jittering), not in the rendering itself. Therefore it is not a GPU intensive task. The result is that the GPU has to do relatively little work when rendering a scene with motion blur compared to a scene where no motion blur is involved. This is also why rendering with motion blur takes longer.

I hope this helps de-mystify the scenario.

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Scott Ellery Feb 22, 2018 10:12 AM

Hi Helge ,

I received the same results when testing , I am sure there is a reason I am just not sure what it is. Ill have to think on it for a bit and test a bit more.

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Helge Feddersen @ Scott Ellery on Feb 22, 2018 11:45 AM

thanks Scott!

i tried a very simple model in SWX. just a rectangle block no specific size. the part itself had about 50kB

put this into visualize and added a rotation animation about Y at 4500 for 5 sec.

first render: motion blur deactivated - GPU at 95%

second render: motion blur activated - GPU dropped to 65% lows and 85% highs

model size seems to influence the story but i think the root cause is somewhere else

looking forward to your testing results

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David Randle

Feb 22, 2018 9:12 PM

I hope this helps de-mystify the scenario.

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Helge Feddersen @ David Randle on Feb 23, 2018 6:19 AM

Hi David,

thanks for de-mystifying this

it certainly apears to be the reason, all be it not very satifying. I was planing to do a animation sequenz of about 20sec in which motion blur would need to be activated.

i finished the 1000 passes in the above test file and ended up with 10min for one frame vs 1:30min. this would sum up to 20sec x 30fps x 10min = 100h render time. if i then put the rest of the Model into the scene the render time is bumped to 23min one frame.

Maybe the Software Gurus at SWX can find a way to optimze this ;-)

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4 Replies

Scott Ellery Feb 22, 2018 10:12 AM
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Hi Helge ,

I received the same results when testing , I am sure there is a reason I am just not sure what it is. Ill have to think on it for a bit and test a bit more.
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- Helge Feddersen @ Scott Ellery on Feb 22, 2018 11:45 AM
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  thanks Scott!
  
  i tried a very simple model in SWX. just a rectangle block no specific size. the part itself had about 50kB
  put this into visualize and added a rotation animation about Y at 4500 for 5 sec.
  
  first render: motion blur deactivated - GPU at 95%
  second render: motion blur activated - GPU dropped to 65% lows and 85% highs
  
  model size seems to influence the story but i think the root cause is somewhere else
  looking forward to your testing results
  Like • Show 0 Likes0
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David Randle Feb 22, 2018 9:12 PM
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Correct Answer
Hi Helge - from what I remember, the majority of the "work" involved in rendering a scene with motion blur is in the translation of the geometry (jittering), not in the rendering itself. Therefore it is not a GPU intensive task. The result is that the GPU has to do relatively little work when rendering a scene with motion blur compared to a scene where no motion blur is involved. This is also why rendering with motion blur takes longer.

I hope this helps de-mystify the scenario.
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- Helge Feddersen @ David Randle on Feb 23, 2018 6:19 AM
  Mark Correct
  Correct Answer
  Hi David,
  thanks for de-mystifying this
  it certainly apears to be the reason, all be it not very satifying. I was planing to do a animation sequenz of about 20sec in which motion blur would need to be activated.
  i finished the 1000 passes in the above test file and ended up with 10min for one frame vs 1:30min. this would sum up to 20sec x 30fps x 10min = 100h render time. if i then put the rest of the Model into the scene the render time is bumped to 23min one frame.
  
  Maybe the Software Gurus at SWX can find a way to optimze this ;-)
  
  Putting your answer as correct
  Like • Show 0 Likes0
  Actions

camera motion blur possibly causing GPU render performance drop

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