Join Mark Christiansen for an in-depth discussion in this video Rotoscope straight-ahead, part of After Effects Compositing 05: Rotoscoping & Edges.
- In this lesson, I'm going to demonstrate straight-ahead articulated roto to remove this guy and add back the board grab. It's about eight frames worth, and it will take me 15 to 20 minutes to do, which I'm going to speed up and add commentary as needed. Let's get started. I'll start with a mask to remove the guy holding the board. I'm gonna work in Layer view. If you haven't heard me say it before, there are a couple of helpful things about opening up Layer view.
One is that, as you draw, there's no causing the layer to disappear. It stays it right there. And the other is that you just stay focused on the mask you're drawing. I'll label the mask. Labeling the mask is a big favor to yourself as you move forward and create multiple masks. Once you've made more than one or two of them, it can be hard to remember by color which is which, so I highly recommend it.
So now with the guy removed, the next step is to add the board back in. So here I'm taking advantage of the ability to mix masks, and have one intersect another. So I've knocked out the guy and I'm bringing back just the board. I'll zoom in periodically to make sure that my line is splitting right between the inside and the outside.
So, for example, if I see some of the background creeping in I'll tighten it up, and if I see that the board is cut off I'll loosen it out. This will change as the amount of Motion Blur increases further in the shot. But I should still be able to see that boundary. And go right down the middle of it.
You can instead decide to make your mask tight. So, in other words, I could instead bring it in and then have the option of raising expansion to loosen it a little bit, or I could go loose and tighten it. I think that one is probably the most dangerous option. So my suggestion is eliminate background as best you can, and you can always add feather and expansion to loosen and soften it after the fact.
The bigger picture is that you really just want to be as consistent as you can. And this takes a little practice. You're gonna notice that if you make the edge kind of tight and cropped in one place, and loose in another, then it's gonna make your life a lot harder when you're trying to adjust the mask overall. I'll move the pivot point to rotate the board into place on each frame. The pivot point is a little hard to see here, but it's this really useful thing when you're dealing with organic motion to decide where it rotates from.
Note that I have to move the pivot point each time. It doesn't hold it's place. So if I don't get it quite right, I have to try again. So now I'm going to go through the trickiest part of the roto here, the most delicate part, which is going to be getting this board accurately rotoed while it's in motion. And so I'm doing this frame by frame because, although the motion does go in somewhat of a consistent arc, I don't think there's any way to purely keyframe it.
So I'm doing what's called straight-ahead roto here. And so what I'm watching out for as I do it is just maintaining consistency as to how I draw all the edges. Now the softness is gonna come in at the end when we turn on Motion Blur to match the motion of the shots. It's almost as if I have to imagine the board without the blur, and just draw the edge that would be there if there were no Motion Blur.
Motion Blur, in this case, you could consider it to be going in both directions. It's kind of like a long smear, and what you see in one frame is basically the average of that smear. So by drawing in the middle, you're actually getting the center of the average, and then you're letting Motion Blur in After Effects recreate the accurate amount of softness to match the motion of the board.
So you can see that wasn't too bad. You're watching it sped up, but in relatively short order, we're able to isolate out the board. For the most part here we want to leave the shape of the board consistant and let Motion Blur take care of what you see here. But I am being a little bit finicky about just making sure that if I see indentations or irregularities that I add them.
Here you can see some, I don't know if it appears to be a slight curvature. The motion is arcing there, and I think that that will be covered by turning on Motion Blur just fine. So finally, I can move in and just make any fine adjustments as needed. And notice I just move the entire layer in Comp view, which is something that cannot happen when I'm in Layer view.
In the next lesson, I'll show you how to prevent ever moving a layer accidentally without noticing.
- Selecting a target
- Applying a mask
- Starting a mask with a shape
- Breaking down shots of clean plates
- Creating points and Bézier curves quickly
- Building articulated rotos with in-between frames
- Adding soft edges and motion blur
- Working with the clone brush
- Getting the most from the Roto Brush