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Colin Alexander
RSMB Vectors
on Dec 3, 2015 at 8:54:06 pm

Hi all,

I'm a 3D product viz artist looking to integrate RSMB for After Effects into my workflow for some of the small animations I do, and I have a couple quick questions.

First off, as far as I can tell, if using any bit depth other than 32 bpc in AE the blur is just always at a 45 degree angle rather than the motion of travel. I created a super simple test comp to demonstrate my issue. In this frame the red ball is traveling quickly directly from left to right.

In 8 bpc with RSMB Vectors applied it looks like this:


In 32 bpc it appears correctly like this:


I also had to drastically decrease the blur amount from roughly 0.5 to 0.02 when going from 8 to 32 bpc, is that normal behavior or am I misunderstanding something? Working in 32 bpc isn't really a hardship as I generally would be anyway, I just thought it was strange how different the result was.

The other issue I'm having is that the whole frame is being blurred regardless of motion. Here is a screenshot of the frame:



The red ball in the background is moving quickly, the red cube in the foreground is moving slowly, and the large tan sphere in the very back is completely stationary, but everything ends up blurred.

My motion vectors for this image are pre-comped and I'm using a linear key color key to cut stationary objects out of the alpha (I saw this recommended on a Digital Tutors tutorial). My motion vectors for this frame look like this (the cube is too dark to make out here, but there is color information there):



And the alpha for those vectors appears as such:



I've read elsewhere that I really need to render the moving and non-moving objects separately, which is fine, but again it seems odd to blur the whole frame regardless of alpha and motion. Does anyone have any insight here? I'm totally willing to accept that I'm an idiot, I just want to make sure I understand what's happening here before I start integrating this into my pipeline.

Thanks,
Colin


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Pierre Jasmin
Re: RSMB Vectors
on Dec 4, 2015 at 1:37:07 am

If your motion vectors look like the red circle then it's not the motion vectors we are looking for

With a static scene it should be 0.5, 0.5, 0 (RGB) - try to get that (and what is your renderer and within what)?


Pierre



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Colin Alexander
Re: RSMB Vectors
on Dec 4, 2015 at 3:42:12 pm

Oh I'm so stupid. Yes, I should have said in the previous post that I'm rendering with mental ray out of Maya, and I was using the 2D Motion Vectors render pass. What I should have been using was the Normalized 2D Motion Vector pass, I believe. This looks more like what you're after, right?:



And of course it has solved all my issues:



Sorry to have wasted time on such a simple issue, the tutorial linked on your site clearly says to use the normalized pass, I just hurried over that apparently. Thanks for your help.

Colin


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Pierre Jasmin
Re: RSMB Vectors
on Dec 4, 2015 at 10:00:03 pm

No worry, it does not help they change the labelling every 2 versions :)

I think they also added a new gamma option that one can trip over... a good sanity check is to render a scene without any motion and make sure you get no motion blur whatever parameter in RSMB you set

Pierre



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