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Paul Sheehy avatar image
Paul Sheehy asked ·

Arnold Motion Blur - Recommended Settings

Hi again,

We are having some issues with render layers - so I was thinking of just rendering the shots as beauty passes with Cryptomatte AOV's. So wanted to ask can anybody recommend some sampling settings to use if we were using Arnold's motion blur? Would they have to be a far higher than a standard setup if we were not using 3D motion blur? What kind of a hit is it?

We could use motion vectors, but that will more than likely give some issues and would need us to split render passes so that is the reason we were thinking of the Arnold motion blur option.

Any help or info would be greatly appreciated, thanks.

Paul

motion blursamplingbeauty
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Stephen Blair avatar image
Stephen Blair answered ·

In general, set everything to 1.

Then set the camera samples (AA) high enough to remove noise caused by the motion blur.

https://docs.arnoldrenderer.com/x/ng1kAg

Then adjust the other sampling settings as required to remove specific types of nose OR keep increasing AA.

Using just AA is simpler but possibly more expensive. Adjusting individual settings (like diffuse) has to be done carefully or you'll blow up your render time.

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Paul Sheehy avatar image
Paul Sheehy answered ·

Wow, that worked. That is an absolutely shocking bug on their part isn't it?? Cheers for that.

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Stephen Blair answered ·

Are you using Nuke?

A workaround in [older versions of eg 10] Nuke, when using RGB color AOVs for motion vectors:

  • create the VectorBlur nodes and set them up (they will look wrong)
  • save the file
  • completely close Nuke
  • reload your file (vector blur will now be correct)
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Paul Sheehy answered ·

Hi Stephen, we have a change of plan on this. We decided that the 3D motion blur will be too expensive for us, for now anyway. So we want to try the motion vector aov and Nuke's VectorBlur.

However, when I am doing a test on a basic scene it isn't behaving as I expect. It is like the vecor one is being blurred in a different direction compared to the proper motion blur. I have attached an image that hopefully explains this a bit better. I cropped the vector one too and placed it next to the 3D Arnold on to show it more clearly. Would you have any suggestions?

motion-blur-comparison.jpg


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Paul Sheehy answered ·

I didn't think I did, but let me check tomorrow and I will get back to you. Hopefully it's just something simple, but good to know it is working for you.

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Stephen Blair answered ·

N and Z are blurred when I test it. Do you have layer overrides or anything like that?

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Paul Sheehy answered ·

Hi Stephen, I just tested it and the Cryptomattes are getting motion blurred, but the normals and depth pass did not. I also added an indirect aov and that got the blur too. Any ideas?

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Stephen Blair answered ·

You don't have to do anything special to get motion blur in the AOVs

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Paul Sheehy answered ·

Thanks Stephen. Should I need to know of any tricks for the Cryptomatte and Zdepth Aov's to receive this motion blur also? I'll let you know how it goes but just asking in advance.

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Stephen Blair answered ·

I was talking about the sampling settings in the Render Settings only.

I would leave the light samples alone for now, and then change them if you have shadow noise (see https://docs.arnoldrenderer.com/x/ng1kAg)

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