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What do I do when "CC Force Motion Blur" makes mistakes?

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Nils Moody
What do I do when "CC Force Motion Blur" makes mistakes?
on Oct 5, 2016 at 12:43:25 pm

Hello dear cow ,

since creativecow.net was a very reliable source to look up in the past I've decided to create an account and be more interactive this time around. But getting straight to the point: A problem with "CC Force Motion Blur" effect convinced me to do that.

Well, I'm using this effect right now and it works like a charm for the most part. But it does some weird things here and there like blurring things which shouldn't be blurry and so on. Is there any way to fix this by tweaking some parameters manually or making a workaround?

Btw I'm working with pre-rendered video and not with moving afx layers. If needed: I'm using 180° and 30 Samples.


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Walter Soyka
Re: What do I do when "CC Force Motion Blur" makes mistakes?
on Oct 5, 2016 at 4:19:09 pm

All effects based on motion estimation are prone to gloopy artifacts where the motion estimation is incorrect. This usually occurs where the boundary between two objects is unclear, or where two different objects are moving in different directions.

You can try tweaking the parameters, but it may not work, and you may alter other parts of your shot (for better or for worse).

You can also try Reel Smart Motion Blur:
http://revisionfx.com/products/rsmb/after-effects/

It will probably give you different results out-of-the-box, and you could combine the results from each with mattes around the troublesome areas. If you have the time to make them, RSMB features manual foreground/background matte, point and spline guidance which can really help clean up trouble spots.

Sometimes, though, the best solution is still the paint tools, even in high-end commercial work.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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Thomas Frenkel
Re: What do I do when "CC Force Motion Blur" makes mistakes?
on Oct 5, 2016 at 4:25:26 pm

Hey Nils,

not sure if you are aware of the "TimeWarp" effect, which can be an alternative for you. You can use it for pixel motion blur on your prerendered footage:
https://blogs.adobe.com/creativecloud/pixel-motion-blur-effect-new-in-after...

Check this for a comparison: https://www.thepixellab.net/beginning-101-free-motion-blur-in-ae

If this doesn't fit your needs, can you post a screenshot of your problem frames? Are they by any chance exactly the start or ending frames of your composition?

Or maybe there are some unwanted keyframes in your compositon. You can deselect all layers, press "UU" and check.


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Nils Moody
Re: What do I do when "CC Force Motion Blur" makes mistakes?
on Oct 5, 2016 at 7:37:04 pm

Hello Gents,

thank you very much for your responses! I knew the TimeWarp-Effect but I forgot that it had the ability to create motion blur (without slowing things down). I'll definitely try this out. Maybe it is better! :] Have you any experience with it? Is it more reliable? Which one are you using?

I was aware that there are some alternatives with a paywall behind it but maybe there are even better. But I try to avoid them all because the cost of AFX is enough for me and many plug-ins are just making you lazy because you can actually do a lot without them. Thanks for the suggestion though! I might give the trial a shot.

By the way, the frames are not the start and ending frames of the composition and it is totally understandable that the motion blur isn't correct at these sections for the most part. Because it's a muzzleflash of a weapon.. which isn't moving in fact. Just flashing, haha.

So how would the paint-tool or the matte solution look like for you guys? Just curious.


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Walter Soyka
Re: What do I do when "CC Force Motion Blur" makes mistakes?
on Oct 5, 2016 at 7:46:43 pm

[Nils Moody] "it is totally understandable that the motion blur isn't correct at these sections for the most part. Because it's a muzzleflash of a weapon.. which isn't moving in fact. Just flashing, haha."

That's the issue. The effect is trying to figure out where those pixels came from in the previous frame and where they go in the next frame so it can smooth the motion.

You might be able to mask out the muzzle flash, replace it with either some clone brush work or the previous/next frame, then add the muzzle flash back on top separately, after the forced motion blur.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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Thomas Frenkel
Re: What do I do when "CC Force Motion Blur" makes mistakes?
on Oct 5, 2016 at 8:34:15 pm

[Nils Moody] "But I try to avoid them all because the cost of AFX is enough for me and many plug-ins are just making you lazy because you can actually do a lot without them."
....and you can learn a lot more. This is a great mind set, to get really good in After Effects.

[Nils Moody] "Have you any experience with it? Is it more reliable? Which one are you using?"
I'm not sure which one is better performance-wise, but I'm pretty sure TimeWarp has the more modern and sophisticated estimation process.

This may be a stupid tip, but did you try simple frame blending (Frame-Mix) for the muzzle flashes? This is usually used for slow motion effects on low fps footage, but it can make your muzzle flash a bit smoother.


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Nils Moody
Re: What do I do when "CC Force Motion Blur" makes mistakes?
on Oct 6, 2016 at 6:21:12 am

I've made a comparison now and I think TimeWarp brings a way better result. There are still some artifacts but it doesn't go all crazy like CC Force Motion Blur does.

So I guess.. now fixing this with maskes including soft edges, right?


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