Join Ben Brownlee for an in-depth discussion in this video What to do first when things go wrong, part of mocha 3 Essential Training.
- View Offline
Fairly often when we're tracking an object, we won't get the results that we need the first time. So what are the first things we need to do to try and fix this? Well, let's take a quick look at where we're at again here. So we've got our object going up here. We've got the track slipping a little bit as it moves off screen there. So, we haven't quite got the results that we need for this one yet. So the first thing I always recommend to do is go back to the area where it starts being a bit of a problem.
In this case it's about frame 95. An, what we're going to do is we're going to adjust the parameters a little bit down here in our track. Well, in this case, I'm going to come in and I'm going to add perspective modelling to my to my motion. And the reason I'm using perspective of course is I've got a rigid box face here, which I know is going to move slightly in perspective. So I'm just going to constrain that there, so that we don't get confused when the motion blur starts popping in. I can't say I do have another key frame along here, located at some point along the way.
I don't want to get confused by that, so what I'm going to do is minimize the number of key frames that I've got and just delete this one here. So if a key frame is not doing anything for you, delete it off of the timeline. And we're going to see this come through time and time again. Where we sort of simplify our time line and our key frames as much as we possibly can. So once I change parameters, I'm going to come down and track this forward with the new parameters going on. And let's see if that gives me any better results. And some of this is difficult to see throughout all of the motion blur. But actually, I think this has given me a better track now.
One of the other things we can do if you've got your model set up how you like it, is we can adjust the minimum percentage of pixels used here. Also, if you've got a clear image, you'll want to turn this percentage up so that Mocha has to get a more accurate result before it moves on. There is a small processing time cost for doing this, but your results will often be better. You might find that having this minimum percentage of pixels used up too high can actually be a problem in itself. And you might want to dial that down just a little bit. Likewise you could find that changing the input from luminescence to auto channel, is actually really what you need.
So that's always my first part of call. Before I try and fix my tracking any other way or try and key frame my shape, what I'll do is I'll find the area. The last good frame actually. And it's at that point that I'll start to change up my tracking parameters. And you'll find that by doing it this way, you're going to get the most consistent results with your tracking. Sometimes you might find you have to take more drastic measures though, and I'm going to demonstrate this by first duplicating my Box front track here. Turn off the tracking and lock my original.
Let's just expand this out and we'll take track 2 here. And I'll give this a separate color. So don't we get confused, I'll make this well not a yellow because that will, because that's going to get lost. Or maybe a lovely bright purple. There we go. What we can also do, is we can also key frame our shape a little bit. And so long as the shape remains coplanar, as long as its described in the same plane that we were tracking previously, this shouldn't be too much of a problem. I'm just going to turn my surface off here, and lets come in and I'm just going to. Let's move this shape down.
Yeah, so I'm just sort of taking all of this. Let's just take in actually this strange area here. And because i'm working on a smaller shape here, I'm also going to come down to my minimum center pictures used and crank that up. So let's crank it up to probably like 60. And let's track that forwards now. Boom, boom. Let's turn the surface on, see what's going on with that. So as we come up, you can see that my surface is drifting a little bit on this side, because we don't have as much information for that anymore.
But you can see that actually the other three points are holding pretty well, right up until the end which starts to move our frame and then everything falls apart. You can see there we do have some flexibility when it comes to keyframe in the shaper. Now of course we scrup through this here. Our shape data is going to keyframe between our first frame, which is where the first keyframe is, and frame 95 where our second keyframe is. So, the shape data now looks really old. But, remember the shape data and the tracking data is separate, so our surface.
Despite what the shapes doing, our surface still remains the same there. I think I still had a better overall track with the first one I did. So I'm going to turn that one back on as my master one, and that's the one we'll work further with. But you can see that when things start going wrong with a track My first solution isn't to try to come in and fix tracking data manually, or add a whole load of key frames to my shape. The best solution is always to try and keep it as simple as possible. So we go back to the last good bit of data, and wherever that was, we'll then start to come in and adjust the tracking parameters up a little bit.
And you will often find that if the main shape you chose to track at that point is good enough, then just by changing up the tracking parameters up a little bit there, you'll be able to get the data and the results that you actually need. If that doesn't work, then we can start to come in and maybe find another co-planar area of the image that we can track. So adjust our shape player up a little bit, and try and track in that new data. Now if those things still don't work 100% but we're sort of in the right kind of area, then we can start to think about more drastic measure like manually key framing things up in the Adjust Track.
But if you're a million miles away from where you need to be, the best thing that you can do, just simply delete that layer and just start again completely fresh. To draw up a whole new shape, fix your parameters up again, and then and then see how that goes. Because it's far better to spend you know, 5, 10, 15 minutes on a new track than it is to sort of try and come in and manually fix things up, where you could be spending a lot longer getting a lot worse result at the end of it.
This course was created and produced by Ben Brownlee. We are honored to host this content in our library.
- Setting up preferences
- Understanding the planar tracker
- Creating your first project and first track
- Tracking rotation
- Tracking objects that move off-screen
- Using the Shear and Perspective tools
- Exporting tracking data to After Effects, Motion, or Final Cut Pro
- Creating a fast rotospline
- Creating complex mask shapes efficiently
- Correcting for lens distortion in your footage
- Generating a 3D camera solve