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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.
The Planar Tracker is remarkably flexible. You can adjust the tracking shape during the tracking process or keyframe the tracking shape before the tracking. Here, we'll take a look at both techniques. We need to load a clip. So we'll click on New Project, Choose, go to our Lesson_04_Media, select the Airport folder and click on 01 airport frame, click Open. Now, for some reason, mocha misunderstands the Pixel Aspect Ratio.
It thinks it's 1.33, it's not. So you just change that to Pixel Aspect Ratio of 1 and click OK, everything will be fine. You'll need to keyframe the tracking shape, when you're tracking target outline, change your shape, either due to occlusion or moving on or off screen. As in all cases, we'll first scrub through the clip to study what's going on, and we'll note the camera moves. Okay, we obviously have an orbiting helicopter shot here. So we're going to have a lot of perspective change.
So we're going to turn Perspective on in our Tracking Motion. Let's take a look at the case of keyframing before. I'll move the playhead to frame 1, draw my shape. The issue here is I need to keep my tracking shape off of the buildings and the airplanes because they are not on the same plane as the ground. So I've drawn my initial shape. I'll scrub through the Timeline, looking for when the airplanes get in trouble. All right! So I'm going to move these away from the planes, and expand my tracking area to incorporate some new material that came into frame.
Scrub through the Timeline, oops! Looks like I'm getting close to my airplanes, so I'm going to pull them away, move that off, get some more material to track, and scrub to the end. I'll just move this last control point away from the airplane. Okay. I've keyframed my tracking shape and so it kind of moves and wiggles as I scrub the Timeline. Okay, we'll start here on frame 1. I could have started tracking backwards from the end of the clip. In this case, it wouldn't really matter.
So we'll track forward and while it's tracking, you'll notice that the shape is drifting funny. Remember, when you keyframe a tracking shape, its keyframe motion and the tracking motion kind of play off of each other and it looks a little weird. But when the tracking is done, everything now looks good. We'll stop that and go to frame 1. The keyframe shape drifts and wiggles, so the planar surface and the planer grid are the only way to confirm the track.
If I scrub through the shot, looking at the shape, I don't get any good clues. I'll turn on the Planar Surface, and I'm going to hide my Spline, so I can focus on it. One good thing to know is that the Transform tools that you use for the shapes can also be used for the Planar Surface. So for example, the E key, I can scale it down, the W key, I can rotate it, and the Q key, I can reposition it.
So I'm going to position the Planar Surface on the ground using these very handy lawn mower marks as a reference for what's straight and parallel. And I'll use these references here to try and determine where to put the back end, adjust the front end here. So I've roughed it in with the Planar Surface and now I'll turn on the Planar Grid. What I want is the Planar Grid to be lined up with everything on the ground. So I'll do some refinements here to get the Planar Grid parallel with the buildings over here, pretty good over here.
I need to touch up this side to get these gridlines parallel to this runway here. I'm not parallel here at this end. So I'm going to reposition this guy, bring that in line. Okay, let's call that good enough, and now let's play our track. Okay. We have a good lock, no drift, and everything is lined up very nicely. I'll stop that, and jump to the first frame.
I'm going to turn off the Planar Grid and the Planar Surface and I'll delete that tracking shape to show you the mixed technique, which is to keyframe during the tracking process. So I'll start up by drawing my shape as before. Again, I have to keep it off the buildings and off the airplanes. Okay. I'm ready to start tracking. So I'll start tracking forward. Watching my shape, now I don't care that the shape drifts off screen, but I'm going to stop it now, because I have some new surface that's been revealed here.
So I want to take advantage of that. So I'm going to extend my tracking shape, so I can get as much as I can in my tracker. I will zoom out a little bit, so you can see the action here on the outside of the frame. Again, the tracker doesn't care, if your tracking shape goes out of the frame, it knows where the edge of the frame is, so no worries. All right! We'll continue tracking forward till we get to another place where I like to stop. I'll stop it here because I now have some more tracking target, I can include in my tracking shape, and we'll continue tracking to the end of the shot.
Now, when I play this, the tracking shape also squirms and wiggles and we cannot use it to determine the accuracy of the track at all. So, once again, we'll stop that, jump to first frame and turn on the Planar Surface. I'm going to hide my spline. I am going to shrink it down, rotate it, reposition it, and line it up with my lawn again. Again, I'm using these lines as sort of a guide for where to put my Planar Surface, although, the nice lawn mower lines are a big help for these edges.
Okay, that looks about right, so I'll turn on the Planar Grid and I'll check. That looks pretty, yeah, I need to touch that up a little bit, get that more parallel there. This is not quite parallel here. I'll move that out there, and pull the back here a little bit. All right! That looks pretty good. This needs a little more attention here. So I'll pull this up here. Make sure that these gridlines are parallel to this runway, these lines are parallel to that building, okay, that looks good.
So let's play this and see our new track. All right! That looks good. we're locked on solid as a rock. Stop that, so in the real world of tracking, your tracking target will often become occluded or move off screen. So keyframing the tracking shape is a very important technique for getting accurate tracks.
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