Learn how to choose a good planar pattern to track.
- [Instructor] This is a good time to discuss how to select a good planar pattern to track. The first thing to think about is how you're going to use the data. And most of the time with motion tracking data, you're going to make a new element, like a new piece of art or a new footage, follow the motion path. In the case of corner pin data, you're going to distort a layer so it fits that area you tracked. So you want to track close to where you want the new artwork, or the new footage.
So for example, if you want to put a new billboard on this building, you track that part of the building. If you want new artwork on the back of this boat, you track the back of the boat. Now it's not always possible to track exactly the point where you want the new art. You try to get as close as possible. There are ways to offset the data later on, and we'll discuss that in other videos. But ideally, you track where you want the new element to be. Now beyond that, there's quality considerations.
Let's zoom into this footage and see what's going on. And this is saved out as 2-1, and this is just the city, no tracking. I'm going to zoom in, and we'll take a look. So we saw that the front of this building was a very easy track, it's very clear. The other parts aren't so good in this particular shot. For example, if I scroll over here to the side of this building, it looks okay at the start, right here. But if I play forward, you'll see that there's a reflection that changes, the lighting changes significantly.
That's a big problem, big lighting changes, whether they're reflections or shadow changes or light intensity changes, those are all confusing to the tracker. Another problem would be something similar, if we look here a little bit later, huge flare. Where the flare is, the light changes. Again, could be confusing to the tracker. Now, if I wanted to place new artwork on top of this building, like a new billboard, that's going to be problematic. The tracking will become incorrect, towards the end of the timeline. What you can do is track something nearby and offset it, and we'll discuss that later on.
But just know that will be a problem area. Beyond that, other lighting changes with this footage would be something like the water. The water ripples, the light pattern changes again, potentially confusing. So aside from lighting changes, there are also issues with occlusion or things simply leaving the frame. For example, tracking a building that leaves the frame would be bad, because as soon as the building leaves completely, the tracking's over. Now planar trackers like Mocha are very robust.
It can actually handle a part of the pattern leaving the frame. So let's say you have a spline shape with four points. Two of the points can actually leave frame, and it still tracks. But if it's in frame the entire time, it would be better. A similar problem is occlusion. If something covers up the pattern, that will confuse the tracker. So there's something in the foreground, for example, or there's smoke, lens flares like we discussed, those are all problems. Associated with that is anything that disguises the pattern, so it's not clear, so heavy motion blur, heavy film grain, things like that, less than ideal.
So think about how you want to apply the tracking data and track as close as possible to where you want that new element to be. And then try to make sure that the pattern's very clear, or clear as possible, is not occluded, and hopefully stays in frame. If you follow those basic rules of thumb, then you'll get a good track. If that pattern is not available, we'll discuss some workarounds for still making the tracking work.