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VFX Techniques introduces common yet critical visual effects techniques that are used in film and television shows on a regular basis. This installment shows how to build complex composites with Adobe After Effects and mocha, where motion graphics are mapped to live-action footage of an actor. Author Lee Lanier starts by combining rotoscoping and effects to digitally apply makeup to an actor to disguise motion tracking marks. Then discover how to transfer footage into mocha and generate planar tracking data that you can use to motion track graphics to the moving face of the actor. Plus, learn how to build and adjust motion graphics to create the look of a virtual tattoo and a pair of holographic heads-up glasses.
We have the tattoo artwork tracked in After Effects, and that's working well. We can now move on to the second piece of artwork we're going to track, which is the heads-up display, which is a set of futuristic glass-like projections over her eyes. To create that we're going to need to do some additional motion tracking. In fact, there's a set of tracking marks above and below her eyes for that purpose. So we're back in mocha now to create a second planar surface and track that. How do you do that? Well, I can just make a new X-Spline shape, and that will create a new layer.
I'm going to go to frame 275 first. I want to see the four dots really easily. I'm going to zoom out a bit, and then I can go and get my X-Spline tool, once again up here, and draw another shape around these four dots. To finish off this shape, I'll just right-mouse click, and there it is. Now this time, I'm not going to make my shape really tight to the edges of the dots. You don't have to do that, you don't have to line this up with some edge.
You're really just defining a pattern within the shape it's going to track. So I'm going to leave a little gap between the dots and the corners. If you see the zoom window at the top left there, we can see what kind of gap there is. So I'll adjust this real quick, bottom left, and bottom right. Okay, and the goal is to get similar gaps throughout the entire timeline once we start to track.
So I'm on frame 275 now. Because I moved these points, I get a keyframe. Let's try a track to the end, track forwards. Now there's very little going on in terms of motion here, so this part of the tracking is nice and smooth. Even knows how to deal with the fact she smiles, but it keeps the shape consistent, which is great. So let me go back to 275. Now before I forget, I'm going to go up to my layer here, and this is a new layer for new X-spline, and just double-click to rename it.
I'm going to call this Eyes. Now if you click of that layer, you can just re select it to see that spline again. But if I select just one, you'll see that keyframe reappear. Remember, each corner point has its own set of keyframes. Okay, let's try to track backwards and see what happens. And there you go.
I'm going to stop now. You can see that the shape is definitely drifted, so let's look for some places we can add additional keyframes. Generally you want to add them when there is a sudden shift in the shape. And that's usually associated with something like a head turn or some action of the actor, in this case. So, if we go to frame 150, you can see that's right before she turns her head. So that's a good place to place additional keyframe. I'm going to reshape this X-spline, and using my window's top left, I can see the current frame, and the next keyframe, and therefore be able to at least make that gap similar between the two frames.
Now, the top right one is a little bit tricky because the perspective shift on the dot makes the gap a little hard to estimate. It's not going to be the same size, it's going to be a little smaller because of the perspective shift. So we'll just have to make our best guess there. So here's the lower right and the lower left. Lower left is probably one of the easier ones here. Okay, let say that's good for now, let's try to track some more. Before I do though, before I go to the beginning, it might be good if to go into the center between 150 and 275, where we were before.
See how it does in that area. Now, whenever you set a new keyframe, what happens is mocha automatically updates all the in-betweens. The tracking curve will update to reflect the new keyframes. There's still some drifting and slipping, mainly because she turns her head right here in this area. So a couple good places for additional keyframes would be, say, 205.
We could quickly adjust that. You'll have to spend more time, this is just very quickly. 224, and then I'll show you also 235, two more places that need adjustments. Let's assume we've got that adjusted to a couple more keyframes in that area. Then we'd go back and finish tracking to the beginning, track backwards.
Right here, there we go. Okay, definitely some major slippage here, so I do the same thing.
Go to frame zero, adjust this shape. Again, doing it very rapidly here. And then determine in between zero and, say 150, where would be good places to place additional keyframes. I'll give you some numbers here just to help out. For example, frame 139, that's the end of that head turn that starts at 150. It's also a 90, 74, and 49.
Now your keyframes don't have to be exactly the same as the ones I just listed, but I found by watching the motion, those are pretty good places to place the keyframes and get good motion tracking. Now I'm going to go back to frame 275 here just for a second, because we haven't looked at our surface, our planar surface. 275 is where we started, so I'm going to go there before I turn the surface on. And you turn it on right here with this button. There it is. Oh, it looks like I didn't enter 275 correctly, I'm on 75.
I'm going to turn that off. Let's go back to 275 again, there we go, and now I'll turn on the surface. And that's what we would expect is the default square shape in this case. I'm going to go ahead and shape this to match my initial X-spline shape. Eventually, I'm going to want to make a more rectangular shape to match the heads-up display we're eventually going to track. But that'll be another step. Just for now, I'm going to follow this practice of just fitting it to the X-spline.
I'm going to turn it off for now because we will have to come back to that later. We added a second X-spline shape, so we could track these new four tracking marks above and below the eyes. That's attached to the planar surface. The tracking worked pretty well, but we did have to make some adjustments with some additional keyframes as she turned her head and moved. Now, I didn't have enough time to finish all those keyframes myself, so I'm going to let you continue that process.
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