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Bayesian anything inside of AE?

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Spencer Tweed
Bayesian anything inside of AE?
on Jun 1, 2011 at 10:35:59 pm

I was recently working on a project with a compositor from ILM and she mentioned Bayesian Matting for correcting a green screen with extreme motion blur.

She explained it as a system for "streaking" pixels on the edge of the matte outwords. So for example if you cut a mask around someone's head and then apply the bayesian filter to it, you could stretch the edge pixels out as far as you want. Basically like adding CC RepeTile to a square with "Tiling" set to Slide.

Anyone know how to do this in AE? Is there anything 3rd party?

Thanks!

- Spencer Tweed


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Walter Soyka
Re: Bayesian anything inside of AE?
on Jun 2, 2011 at 3:09:20 am

I thought that Bayesian matting generates mattes given three inputs: the source image, and two non-overlapping loose mattes that define the foreground and background. It looks in the undefined area and attempts to find the edges. There are a few Photoshop filters that use similar techniques (I use Topaz Remask, for example), but I'm not aware of any AE effects. F_COLOURMATTE from The Foundry's FURNACE will do this, but not on After Effects. I'd love to be wrong about this.

The "pixel streaking" that you're describing sounds a lot like Autodesk's pixel spread node, which intelligently stretches the edges of a matted image, somehow correctly matching colors and angles. It looks absolutely brilliant for correcting keys with challenging edges.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
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Conrad Olson
Re: Bayesian anything inside of AE?
on Jun 2, 2011 at 11:16:51 am

You can create your own version of this. I know it works in Nuke but don't have AE to rebuild it in. If you premultiply your image with your matte, then blur it, then unpremulitply it this will take the colours at the edge and spread them out.

If you do a large blur you will lose detail from the edge but it will spread a long way. If you need to keep the detail you can use a smaller blur and repeat the process multiple times.

Once you have spead the edge out you can combine this new edge with the previous RGB and then premultiply the new image, with the spread out edge colour, with the original matte.

---

conradolson.com


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Spencer Tweed
Re: Bayesian anything inside of AE?
on Jun 5, 2011 at 9:11:16 pm

Hey Conrad,

Yeah she was definitely coming from a Nuke background and had this in it. From what I can tell the technique you explain could work for some things - but I am looking for more detail in the edges. By blurring it all of my colors will fuzz out (though the matte will stay intact).

I guess what I am looking for is a vector blur that blurs the edges straight out - as opposed to all directions (like gaussian blur).

- Spencer


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Conrad Olson
Re: Bayesian anything inside of AE?
on Jun 5, 2011 at 9:14:27 pm

Fair enough. You can get close if you repeat the process lots of time with a small blur value.

---

conradolson.com


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Spencer Tweed
Re: Bayesian anything inside of AE?
on Jun 5, 2011 at 9:08:10 pm

Hey Walter, I know what you are talking about. That is a matting technique that uses Bayesian filtering to generate the matte (at least that's what I understood from the article that I read). I would also love to see this in AE - but I bet it is pretty difficult to get working on video.

Do you know what the name of that Autodesk node is? That is exactly what I am looking for.

- Spencer


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Walter Soyka
Re: Bayesian anything inside of AE?
on Jun 6, 2011 at 5:50:15 pm

[Spencer Tweed] "That is a matting technique that uses Bayesian filtering to generate the matte (at least that's what I understood from the article that I read). I would also love to see this in AE - but I bet it is pretty difficult to get working on video."

I'd think video might actually help it -- for those edge pixels that the algorithm has low confidence about, it could track forwards or backwards to find the same pixel at a different time that might be easier to classify as foreground or background.

Of course, making the two mattes tight enough to get good results could be a challenge...


[Spencer Tweed] "Do you know what the name of that Autodesk node is?"

I'm referring to a Flame FX feature called Pixel Spread [link]. Grant Kay shows it in action on his Smoke blog post Better keys and more with Pixel Spread! [link]

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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Spencer Tweed
Re: Bayesian anything inside of AE?
on Jun 7, 2011 at 4:19:54 am

Yup - that's pretty much exactly what I am talking about. Thanks for spotting it! Now I just need that in AE...

Here is what I think you were originally talking about: http://grail.cs.washington.edu/projects/digital-matting/image-matting/

Very cool stuff, but not what I was thinking of (though that too would be quite amazing in AE)


It is quite a shame that After Effects gets left behind in these "higher end" fields. There are quite a few effects that people don't bother to port over to AE, but if they did I'm sure they'd make some $$. Then again if Adobe got really serious and put this sort of thing (along with some 3D tools) into AE then they could gain back a large portion of the Nuke and Smoke guys that they have lost.

- Spencer


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Walter Soyka
Re: Bayesian anything inside of AE?
on Jun 8, 2011 at 2:00:13 am

[Spencer Tweed] "It is quite a shame that After Effects gets left behind in these "higher end" fields. There are quite a few effects that people don't bother to port over to AE, but if they did I'm sure they'd make some $$. Then again if Adobe got really serious and put this sort of thing (along with some 3D tools) into AE then they could gain back a large portion of the Nuke and Smoke guys that they have lost."

Unless Adobe shocks the world and re-engineers AE to support node-based compositing, a true 3D environment, and pipeline integration tools, it will be ever thus. I don't know that I'd even consider AE and Nuke to be competitors -- they actually have complementary strengths and weaknesses.

What I would would really love to see is for Adobe to add OpenFX support to AE, so that a product like F_COLOURMATTE can be used in Nuke and AE (as well as Fusion, SCRATCH, Baselight, and Mistika). I'm sure there are many developers who would like to see this, too.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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Barnaby Bretton
Re: Bayesian anything inside of AE?
on Jun 14, 2011 at 6:47:52 am

Sapphire Distort - set to FINE will produce the same result as Flame FX Pixel Spread. Flame guys have been doing this for years before Flame FX came out.


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Walter Soyka
Re: Bayesian anything inside of AE?
on Jun 14, 2011 at 4:34:39 pm

[Barnaby Bretton] "Sapphire Distort - set to FINE will produce the same result as Flame FX Pixel Spread. Flame guys have been doing this for years before Flame FX came out."

Beautiful -- works perfectly. Thanks for the tip!

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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Spencer Tweed
Re: Bayesian anything inside of AE?
on Jun 18, 2011 at 5:10:10 am

Genius! Now I just need Sapphire... My day will come...

- Spencer


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Joel Arvidsson
Re: Bayesian anything inside of AE?
on Jun 25, 2011 at 4:50:01 pm

Is there any examples on using the Sapphire Distort as pixel spread? Not sure how you suppose to connect.

joelarvidsson@gmail.com


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