Problem with motion blur

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Karhu
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Problem with motion blur

Post by Karhu » Wed Apr 18, 2018 12:47 pm

Hi everybody,

I came across to a problem when I apply motion blur and render my animation.
I am sorry, but I can't share the actual work file because of my client.

My character has semi-complicated rig created with smart bones, including head turns etc.
When head gets turned, there is some masking and layer ordering happening.

When I apply motion blur (Motion blur on, Sub-frame motion blur on), it does not render correctly, as the attached image shows. Image shows characters forehead and some hair.
Multi-threading on or off, it doesn't change anything.

Image: https://imgur.com/a/Ygzqw

Is this bug or known issue or what?
I have tested this with Intel 2600K and AMD Ryzen 1700.

Thank you!

-Karhu
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chucky
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Re: Problem with motion blur

Post by chucky » Thu Apr 19, 2018 1:27 pm

That sure looks like a bug.
Perhaps you could delete most of the bones and most of the vector points, so you can upload a file that has no resemblence to the final product?
This looks like a bug worth reporting.
Sequential offender.
my latest animations
Karhu
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Re: Problem with motion blur

Post by Karhu » Sun Apr 22, 2018 6:48 pm

Thanks for the reply.
Will see if that is possible or if I can track it down and spot the bug.
It does render some masks and layers still as they should. So issue seems to be on certain layers then.
thewalkerd
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Re: Problem with motion blur

Post by thewalkerd » Mon Aug 20, 2018 2:13 pm

Old topic, but I'll share some thoughts so maybe it can help other guys trying to mess with Motion Blur.

Motion Blur in Moho is kinda buggy at times.
Some things get rendered wrong (parts linked with dynamic bones and Switch Layers sometimes, iirc), and I'm pretty sure it's a bug thing.

I did found a work around for all the bugs I was facing though.

Activate Motion Blur only on the main Bone Layer. Then to correct render bugs, create a new Vector layer under it and activate Motion Blur on it too (it needs to be empty, because it with not be affected by motion Blur after this). If it doesn't help as much, you can try tweaking the Vector layer position inside the Bone Layer (I leave it close to the first layers in the hierarchy).

1st frame can become blury after rendering. That's due to another bug, where Moho creates a blur interpolation between frame 0 and 1, over frame 1. You should delete this frame after render, or not render it at all, by moving the Sequence before rendering.
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Greenlaw
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Re: Problem with motion blur

Post by Greenlaw » Mon Aug 20, 2018 4:51 pm

FWIW, I prefer to render my motion blur as a post effect in compositing.

In AE, I use either the native Pixel Motion Blur or use the third party Reel Smart Motion Blur plugin. RSMB is faster so I always try that first, but if the renders have MB artifacts, I switch to PMB. PMB can also generate artifacts but they're different so sometimes it can look much better (and vice versa.) The animated titles I did a few years ago for Hearts Like Fists used AE's Pixel Motion Blur throughout.

I used to use RSMB in Fusion but we now have optical-flow-based motion blur tool (in the paid version, not free). I haven't tried that with Moho comps yet.

It would be great if Moho could output motion vectors to improve the accuracy of post-processed motion blur in compositing. This is what I typically do for 3D animations. It's just more efficient to keep animation in an 'animation' program and motion blur for an 'effects' program.
D.R. Greenlaw
Artist/Partner - Little Green Dog | Little Green Dog Channel on Vimeo | Greenlaw's Demo Reel 2017
Lead Digital Animator, Dreamworks Animation

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chucky
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Re: Problem with motion blur

Post by chucky » Mon Aug 20, 2018 5:05 pm

Hmm, I have RSMB too but it's so indiscriminate.
The beauty of moho moblur is that you can isolate stuff to blur without compositing.
I just find it a pain that we can't save moblur presets and have to remember settings even if we only use the effect once every now and again.
Sequential offender.
my latest animations
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Greenlaw
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Re: Problem with motion blur

Post by Greenlaw » Mon Aug 20, 2018 5:39 pm

Layer Comps. :)
D.R. Greenlaw
Artist/Partner - Little Green Dog | Little Green Dog Channel on Vimeo | Greenlaw's Demo Reel 2017
Lead Digital Animator, Dreamworks Animation

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Greenlaw
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Re: Problem with motion blur

Post by Greenlaw » Mon Aug 20, 2018 6:03 pm

Trivial sidenotes:

In general, we (me, and the studio where I work) avoid using motion blur in 2D animation. This is mostly an aesthetic choice, but also just to save time.

I used a lot of motion blur in HLF because that project was designed for kind of a 'photographic' look and motion blur was used to enhance that look.

At work, we use motion blur to remove 'stuttering' from sweeping camera motions or quickly scrolling backgrounds. Also, we have a special test that flags 'strobing' animations that may potentially cause seizures in some people, and motion blur is one of the tools we employ to pass the test.

I don't always use optical flow tools like RSMB and Pixel Motion Blur to add motion blur. Depending on the motion effect the scene calls for, I might use a simple directional blur or a radial zoom effect. Sometimes these can look better than 'realistic' motion blur effects, and they generally render faster too.

In 3D, motion blur data can be saved to an auxiliary channel called Motion Vectors. This data is usually embedded in an EXR file along with the main RGB image and a lot of other channels useful in compositing, like depth, object and material ID's (for instant mattes!), etc. Some compositing programs, like Fusion, can recognize these channels and activate them for effects like motion blur, DOF, fog, lighting, masking, tracking, etc. Some of this data wouldn't make sense in a 2D animation but I would love to get similar output options from Moho renders in the future. (But first, Moho needs to support higher bit depths...in these days of HD television, that's a much bigger deal I think.) :)
D.R. Greenlaw
Artist/Partner - Little Green Dog | Little Green Dog Channel on Vimeo | Greenlaw's Demo Reel 2017
Lead Digital Animator, Dreamworks Animation

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