Join Mark Christiansen for an in-depth discussion in this video Refining a matte, part of After Effects CS5 New Features.
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So here I've taken an initial pass at a Roto Brush matte for this figure of a jumping snowboarder. With a challenging matte like this, the key to removing the figure from the background is careful use of the Refine Matte tools that are found under the Roto Brush effect. And we'll take a look at the initial state of him already being matted out so we can talk about refining this further. So that's the result of carefully getting his paint down and you see that there are still some problems. The chief among which is that this is just not a very nice looking matte.
It's got quite a bit of the blue sky coming into it. It looks pretty quantized and rough and there is no motion blur on it. Well, all of those can be solved by the Roto Brush effect itself. We'll just take a look here for the effect controls and here's the Roto Brush effect, which has in it this Refine Matte toggle. As soon as I turn that on, if you notice -I'll undo and redo- that becomes an improved matte right off the bat. And if I switch here to the alpha channel, you can see before, after.
It's got more thresholding. It's softer. It has a nicer shape. So, we've already got a much better result just by having chosen to refine this matte. But there are still some things that could use work. As I go through the frames, I am seeing a lot of chatter, especially back here and even some not very nice looking artifacting down here. There's still quite a bit of blue. One thing that I can do is turn on Higher Quality Motion Blur. That's immediately going to clean up some of that not so nice stuff that was happening over here, and I don't know if you can see the difference but it's pretty clear.
Next thing that I can do is work on the matte decontamination that you see here. The Decontamination Amount is already at 100%, but I can extend it by an amount of my choice so that it reaches further into his boundary. So, this is just looking outside the matte and inside and using more of the inside color. You can see the area that's being affected by choosing View Decontamination Map. I'll just expand this so you can really see these.
Okay, so that's starting to look a lot better. There's still some chatter and way back up at the top, still in that area that I was pointing out, I do have this Reduce Chatter option. Somewhat linked to that but often hard to use is Smoothing. The thing about Smoothing is it will definitely round off some of the details. So Smoothing for something like this is probably going to be used pretty sparingly. But at this point, I'm ready to zoom out and just take a look at what I've got.
Okay, this is a matte that still could use some improvement, but you can see that the matte is a lot less noisy, a lot cleaner, and smoother. Roto Brush is a surprisingly powerful tool, even removing a figure or object entirely from an action-packed shot. By carefully managing the paint process and making use of the Refine Matte tools, you can get an amazing result with a fraction of the time and effort of actual hand-keyframing of masks.
- Comparing After Effects CS4 and CS5
- Working in the CS5 Timeline
- Importing RED footage
- Selecting with the Roto Brush tool
- Optimizing performance and memory usage in a 64-bit application
- 3D image warping with Freeform AE
- Optimizing selections with the Refine Matte effect
- Changing color with Color Finesse and updated blending modes