4 Replies Latest reply on Feb 23, 2018 6:19 AM by Helge Feddersen

camera motion blur possibly causing GPU render performance drop

Helge Feddersen Feb 22, 2018 5:23 AM

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

Re: camera motion blur possibly causing GPU render performance drop

Scott Ellery Feb 22, 2018 10:12 AM (in response to Helge Feddersen)

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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- Re: camera motion blur possibly causing GPU render performance drop
  
  Helge Feddersen Feb 22, 2018 11:45 AM (in response to Scott Ellery)
  
  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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Re: camera motion blur possibly causing GPU render performance drop

David Randle Feb 22, 2018 9:12 PM (in response to Helge Feddersen)

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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- Re: camera motion blur possibly causing GPU render performance drop
  
  Helge Feddersen Feb 23, 2018 6:19 AM (in response to David Randle)
  
  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
  
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