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mocha has always been very popular as a tracking tool, but with the rising interest in stereo 3D conversion, its rotoscoping capabilities have become a favorite player in that pipeline and sales have soared. In this course, Steve Wright covers the basics of operating mocha, as well as advanced tracking and rotoscoping techniques. The course also covers the mocha/Nuke stereo 3D production pipeline in detail.
There are two situations where you'll need to get into the manual tracking. the first is when the target is not a planar surface, so it's not trackable by the planar tracker, so you'll have to hand track it. The second is when you have a few frames of bad tracking data you need to delete. So let's load a clip, go to New Projects > Choose > Lesson_04_Media > Airport and select an airport frame, Open. Don't forget to tell it the Pixel Aspect Ratio is really one and then click OK.
If you've already loaded this clip, you'll have a Results folder in the airport.mocha file, and we can say, Yes we want to overwrite the old one. Manual Tracking is all about the planar surface not the spline. So I'm going to do a manual track on this nice easy target here, so I'll just throw out the spline. I don't care about the spline. I care about the planar surface. In fact, I'm going to hide the spline. In this example, I'm going to hand track the corners to the runway. I'm going to rename this hand track and come down here to select Manual Track.
Notice the planar surface has become this dotted outline. Okay, we're ready to line up the corners, so I'm going to just take these corners, line up here, this one over here, that one there, that one there and you'll notice we now have a control point on the timeline under Manual Track. Let's zoom in, I'll fine-tune the position, and there is my first frame.
Okay, let's go to the last frame. We'll slide the playhead down here. Pan over. remember that the Transformation tools move a planar surface. So Q, pick it up, move it over here, W, rotate into place. Now I'm going to reposition all of my corners again. So I'm actually hand tracking the tracking data. The planar tracker has nothing to do with this. Of course, hand track data is never as good as real track data.
All right, I've keyed my first and last frame. Let me cruise to the middle, see how much it's slipping. So I'll find my most extreme frame somewhere around here, and I will move these points into place. Notice the zoom windows on the left of the Viewer. It says, Previous Frame, Current Frame, Next Frame. When I line up a point you'll notice that it's moving all of them, Previous, Current and Next, but if I place the point where I wanted, then let go and re-click, everybody realize it's sort of the refresh issue.
So I'll come down here, click and drag, and now I've the Current frame set correctly, but Previous and Next are messed up. Let go, click, and everybody is back in shape. Okay, we'll do the last one here. Okay, great! I'll reset the Viewer with the Asterisk key. We'll play our clip, and see that our tracking looks pretty darn good. Now I'm going to draw a new X spline, first I'm going to turn this one off, over here like this. Oops! I don't need the planar surface, so I'm going to kind of roughly line this up with the ground plane.
Okay, same thing for the head. Okay, so that's about lined up with the ground. Now this spline of course, has no tracking data. What I'm going to do is link it to the hand track data. So with Layer 2 selected, I come down Link to track Layer 2, to the hand track and now it's linked to my hand track data. And we'll play that and there we go. Pretty darn good for hand tracking. There's another way you can hand track the planar surface and that's instead of doing the control points move the entire shape.
To look at that, we'll need to load a new clip. So let's go to New Projects. We don't need to save this, unless you want to. We'll choose Lesson_03_Media, the Coffee Cup clip and Open and click OK, and again, if you've already saved the script and it's okay to overwrite it, we'll click Yes. If it's not okay and you click No, you have to refill out the new project and redirect the script to another directory to avoid overwriting it. All right, let's say that our mission is, we want to track this head.
I have to do a roto and I want some tracking data that help speed up my roto. Well, let's see what happens if we try to track the head the usual way. So I'm going to draw a head spline here. Okay, and just tune up these edges a bit. The roto I want is for the entire head, not just the face, and I'm going to rename this head track.
So let's track the head and see what happens. I'll track forward. The Planar tracker is seeing the face and the bill of the hat and that's spoofing the tracker. It's getting kind of lost and confused, and at the end did you see that little waggle with the cup? The coffee cup came in and the tracker spotted that and went amuck. Okay, well, let's bring this back to frame 1, and we'll lock this close the tracking cog, so it won't be re-tracked, and we'll hide the layer.
Now let's do a hand track. Again, I don't care about the spline. I'll turn on the Planar Tracker. I'll rename this hand track. Hide my spline, switch to Manual Track. Again, this spline has absolutely no tracking data. So now that I've Manual Track selected I get my dotted outline again, and once I move my planar surface, I'm going to get the first keyframe here on the timeline.
Okay, so I'm going to hand track keyframe this over the length of the whole clip. I'll scrub out to here, find a good stopping point, set my out point, use the Transformation keys, and let's say I like that. I'll move to the next extreme, right about here. Shift my Out point, move my In point to here. I'll repo. All right, let's say that's good enough.
I'll move to the next extreme right about here before the head tilts up, move my Out point. Move the In point to the last keyframe. Adjust my Planar surface accordingly. All right, let's say I like that. Move to the next extreme, okay, where the head goes all the way over like that, set that as my next Out point.
Move the Planar surface and rotate it. Move my In point, play that section. Remember, my objective is a roto for the outline of the head not the face. So I don't want the bill of that hat contaminated my tracking data. All right, so we'll move out here. Go to next extreme where the head stops right there. It starts to move back, make that my new Out point, pull in my In point, my last keyframe.
Repo a little bit. Okay, now I have a little up movement here so I'm going to move that up a little bit. Okay, all right, cruise over here for my next extreme, the head stops moving right about here. Make that my Out point. Bring in my in frame to here. Again, divide and conquer in small segments. Move it over.
Rotate it upright. Fine tune the position. Okay, let's say we like that. And lastly, over here at the end, I'll set the Out point to there. Move my In point to the last keyframe. Play that, study the motion. So it moves a little bit to the left and down. All right, so we'll move a little bit to the left and down.
Okay, I'll reset my In and Out points. Jump to the beginning of the clip and play. Okay, so this is hand track, so it's a little loose, but at least it doesn't suffer from the interferences of the bill of the hat and the coffee cup. All right, we'll stop that. Jump to the first frame, we'll hide that. We'll turn off the tracking cog, so we don't accidentally track it. In fact, we might even lock it. Now I need to draw my roto shape and link it to the hand track.
To do that, I'm going to make a copy of the head track. Turn off the Overlay, turn on the Spline. So I'm going to make a copy of the head track, so I can compare apples to apples. that my head roto will be identical with the head track, only driven by the hand track data. So I'm going to duplicate this layer and I'm going to call it head roto, because this is my actual roto shape. Of course, I'm going to unlock that.
So if I select the head roto shape, and then I say, here's Link to track is None, the head roto now has no tracking data and doesn't follow the character. So I'm going to link it to my hand track data here. I'll turn on the Mattes, and we'll play it. Now the fit is a little loose, but it doesn't exhibit any of the weird behavior of the regular head track. I'll compare them.
Stop this, first frame, turn off the head roto, turn on the head track. See how much it slips off. It's got that little boop at the end. I'll tell you what, let's fix that little bump at the end of the timeline right there, okay, where I got spoofed by the coffee cup. So here I'll show you the third technique, which is deleting bad data. I'm going to unlock my head track, turn off the Mattes, turn on the Planar Surface, because that's the guy I'm interested in, and we'll hide this spline, because we don't care about the spline.
We'll turn on Manual Track, so we can see all of our tracking control points, and we'll find the frame where our troubles begin, we'll zoom in. So I'm single stepping now. Okay, right here is where the coffee cup starts to spoof the tracker. It shrinks it. So, I'm going to delete this keyframe. Use the Arrow key, go over one more frame and delete that keyframe, and now the Planar Surface no longer twitches at the end of the clip.
I'll turn off the Planar Surface, turn on the Spline, turn on the Mattes. And now the head track shape doesn't twitch anymore. So Manual Tracking will allow you to hand track where the planar tracker cannot help you. It's also where you go to delete any bad tracking keyframes.
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