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In this course, professional animator and director Lee Lanier shows how to create render passes in Autodesk Maya, recombine the passes in Adobe After Effects, and motion track the passes to live-action video footage that contains a moving camera or a moving character. The course covers both the Render Layer Editor and mental ray contribution pass systems. Additionally, 1- and 2-point motion tracking and match moving, stabilization, and 4-point corner pin tracking are discussed.
We have applied the motion tracking data to the render layer, and now the motion tracking is working where the spyglass follows the hand of the actress. One thing we had to do though is spend a little bit more time working with the anchor points. Because there is a little bit of slide based in the way the spyglass is rendered in terms of it's sliding left, right, up, or down compared to her hand, we had to keyframe the anchor point, and it took me a total of six additional keyframes to make the motion look better. Let's play it back there and see what it looks like. So the spyglass is following her hand fairly well.
It looks like it's right there where her fingertips are. Now, one problem of course is the fact that the spyglass handle covers up her hand. This should be really in between her fingers. This is a common problem with visual effects compositing. You have a CG Render, you have to put it behind something that was shot in the real world. So, how do you do that? Well, the best way to fix that is through rotoscoping, which is a very common task. With rotoscoping, you can create a mask, and that mask will affect the Alpha channel of the layer you apply it to. Therefore, we can draw a mask to cut out the bottom of this handle.
So, let's give that a try. I'll go to frame 1, or frame 0, zoom in. What I can do is select the render layer, and then draw a mask with the Pen tool up at the top. With the Pen tool selected, I can click in the Viewer, and each time I click, I get a mask point. So, I'm going to outline the top of the fingers here, because this is where it's going to cut, and then drop down, and just make it extra big down here. Now, I do need to make sure it's a closed path all the way around. So, if I click on the very first point, I get that little circle icon, and I can close that path.
As soon as it's closed, that mask is going to start working. Now, in this case, it saved the lower handle, and cut out the rest. What happens is whatever is inside that closed path becomes solid Alpha, in other words, it's kept. Anything beyond the mask becomes transparent Alpha and is tossed away. So we want the opposite result. We want to keep the top to get rid of bottom. You can do that by going to the Mask options. Once you draw a mask, and go to the Masks section on that layer, and there is Mask 1, expand that, and you have a few options here.
In this case, you want to check on the Inverted Checkbox to get the opposite result. So now it's starting to work. Now I'm going to have to keyframe this mask's changing shape over time because her hand is in different position, therefore this rotoscoping has to change over time too. Before we get to that though, I want to adjust the mask a little bit further. Now, one thing you can do to see what the quality is, is hide this from the Viewer. So I can go to the Toggle Mask button, click that, and that yellow line goes away. However, the result is still there, I can still see what's happening.
So it looks pretty good. However, there's a really hard edge there in terms of the transition. So another thing you can do is go to the Feather on the mask, and increase that, and go from 0 to 3, and that gives me a softer transition. That actually looks better, and is a better match. I will zoom out again and then turn on the Mask. Now, right now the mask has some very hard corners. There are different ways to make softer transitions between the points. One I like to use is called RotoBezier. So, what I'll do is pick the entire mask, and then go to the Selection tool, double-click at the mask lines until the entire mask is selected.
I can tell it's selected because all the points are solid, which means they're selected, and also there is a big Transform Box around it, but I just want to pick the entire thing. I then go up to layer, go to Mask and Shape Path and go to RotoBezier. This converts the mask into a special version, where it's a little bit easier to get smoother, or harder, transitions interactively. Once I have converted it, I can click off this to pick nothing, and then for instance pick one point by clicking on it so it becomes solid and then change that to become smoother, or harder, and there's a special tool for that.
I'll go up to the Pen tool, click and hold down. There's something called Convert Vertex tool. When I pick that, I get the special arrow up here, and I can then place it over at that selected point. I'll see that arrow there in the Viewer also. Then I can click-drag left or right. It interactively makes it harder to the left, or smoother to the right. Once it's converted to RotoBezier, it becomes really easy to convert these points, and interactively change whether you have a hard corner, or a soft corner. So I can click on one at a time with this tool, click-drag left or right, and affect the way that point is transitioning.
So, this is actually a better shape, it's smoother, and it matches the fingers better here. So I'm going to go back to my Selection tool. Now again, I am going to have to keyframe this, but I think we're ready to do that now. So, while I'm on the first frame, frame 0, I'm going to click the Time icon beside Mask Path. That gives me a keyframe right there. Now, the keyframe stores the entire shape of that mask. So now I can go to additional frame, or a later frame, and change the shape, and get additional keyframes. So, I'm going to go to frame 10, and then change the shape. In order to change the shape, what I can do is click off of the mask to pick nothing, and with my Selection tool selected, click on one point at a time and interactively move it to reshape that path.
As soon as I reshape the path by moving points, I get a new keyframe. So, I want to do this for the entire timeline. Now, I don't need to do it for every single frame. In fact, there are several ways to approach it, one is to simply jump ahead every 10 frames, maybe another would be to bisect where you go to the end frame. Next, you shape it, and then go to a center frame. You bisect what you already have. Go to some center position, change the shape, and then go to another position that's in the center of your old keyframe, so you bisect old ones.
Again, reshape your mask, and then continue to bisect. In this case, because the motion is not that big, it's relatively subtle, this works fairly well. I'm doing it fairly quick though, you defiantly want to spend some time to make sure that the mask is following the fingers accurately for the entire duration. So, it might take a few more keyframes. Another thing you can do when you adjust the mask is move the entire thing as one unit, and we have already seen that when we select the mask by double-clicking, get the Transform Box. If you see the Transform Box, you can click-drag in the center, and move the entire thing as a single piece.
This is often very useful. Again, if I were to do that, I get a new keyframe, or it overwrites old keyframe. So, let's turn off the mask so we can't see it here, and let's play it back, fingers, and the rotoscoping is left in, so it's okay. Now, you will probably want to spend more time on yours, but that's a general idea in terms of how to apply it, and how to make it cut out the handle. rotoscoping has allowed us to place the spyglass behind her hand, or at least make it look like it's behind her fingers. We're now ready to move on to other steps where we further integrate the spyglass, so it better matches the footage.
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