You're watching the free version
of Mocha Essentials Follow along with projects and footage with the Premium download. Available at borisfx.com - [Ben] Hello and welcome to exercise four where we're gonna be looking at some more tracking techniques for dealing with difficult types of footage. We're gonna look at three
different types of shots. One is to show a little technique we can do with the planar tracker when we have lots of reflections changing over on the screen. The next one is when we
have something passing in front of where we're trying to track. So tracking occlusions and the third one is where we track when
something goes off screen and what we can do when we
have a longer camera move, as we have in this shot here. Okay but let's start
off with our first shot and see how we get on with this one. So I'm gonna apply Mocha
and let's see what we've got and let's play back and
take a look at the shot. This is always the first
thing that you should do when looking at tracking something, just take a few moments to
analyze what the shot's doing and identify any potential
problems you might have here. Now, this screen is actually
quite a tricky one to track for a number of different reasons. The first one is we have a
curved edge to the screen. So that means that this area here is not completely co-planar, where the screen curves around, obviously. This edge of the curve here is obviously more in keeping with a side than it is the front of the phone. So that's a little wrinkle
we have to think about. And the other big one is
we have a large number of reflections going
across the phone as well. So we can see there. Reflections are what is gonna
give this shot a lot of life but it does make it very tricky to track. Lemme show you what I mean here, if we just try to do what
we would traditionally do. I'll just take a shape, an X spline and X spline rectangle and
just put it around here. Just going across the
entire front of the phone. Obviously, we're starting in the middle, we're starting where the shape
is biggest and most clear and most front-facing as well. Okay and let's come over to
our track motion options. We know this from the previous exercise that we are looking at
a perspective change and I'll set up my surface very quickly. Move that around there-ish. There we go and just so we can see this, I'm gonna come into my layer properties, go to my insert clip and
I think I'll use a grid, an eight by eight grid. So come back into the essentials and let's track that forwards. And it looks pretty good. I mean, there's a bit of slipping but generally speaking,
it looks pretty nice. So let's track it backwards. And this is also relatively smooth but there is a slight, there we go. When the reflection comes over here, you can see the grid begins
to pull up, see that there? So when the reflection comes in, it starts to pull 'cause we're tracking in a bit too much information so we're getting a lot of the
reflections coming in there. Now, Mary has already shown
you how to cut out this shape, how to add another shape to this layer to get rid of some of these reflections so that we're not tracking them. I'm gonna come into my layer properties and turn my overlay off so that
we can see this a bit better but I'm gonna show you a
different way of handling this, that can often be faster and
sometimes just more successful than adding more shapes to a bigger one. I'm actually just going
to get rid of this layer, I'm not a big fan of this. So I'm just gonna come in
to the little trash can here and delete the selected layer. Now let's create a new rectangle spline. I'm on the same starting point here and I'm gonna create a smaller shape. So I'm going to create a shape
just at the top of the phone. There we go, I'm not gonna
think too much about it. We're gonna do this and
then see what happens to it. And I'm gonna try not to
take in the curved edges as much as we can. And we'll see what that does. And what we're doing here
is we're leveraging the fact that Mocha's tracker is a planar tracker. The tracking data that
we get from the surface is going to be that planar shape, that planar movement. So that means we can extend that tracking data out for
all co-planar elements. Okay and to give it a bit more of an Apple to Apple's comparison, I'm going to insert my
eight by eight grid again, come back to the essentials,
set this to perspective. And I'm gonna track this backwards, just with this small shape up at the top and let's see what happens. Okay, so that doesn't look as successful. And the reason for that
is pretty straightforward. We're giving it a smaller shape to track. So any problems and any
mistakes that it makes on tracking that shape, are gonna be amplified out
across the rest of the plane. So that's why we're
getting a bad result here. So let's see what happens if
I add another shape to this. So I'm gonna press and hold
on my rectangular shape tool and I can come down and I
can choose what type of shape that I'm drawing. I can either do an X spline
or Bezier spline rectangle or if we have the X
with the plus next to it or the B with a plus next to it, then I can add a shape to the
layer that I'm working on. So instead of creating
up a new layer each time, we can add multiple
shapes to a single layer. And let's see what
happens if I just add in another rectangle to the bottom down here. So you can see now, I've certainly got one layer in my layers which is the layer two that we had. And I'm gonna retract
this and see what happens. And take a look at that. That is giving us a much more solid track than we had previously. I have our track forwards now and I'll play that back. We have a nice, consistent and
probably near perfect track created just with two small shapes rather than with one big
one or with one small one. But just one final thing here, note what I've done with
the placement of the shapes. And I'm gonna come up to view and I'm gonna go to mats and gotta go to all mats there
and let's come back into mats and I could use the shortcut
and show us the overlays here. And in my layer palette, I can come over and give
these a better color so we can actually see them. When we're creating multiple shapes, what we want to do is
we want to have shapes that cover that plane as much as possible. Instead of just having one
shape just down at the bottom or one shape just up at the top or two shapes just at the top because I've got good areas for tracking at the top and the bottom. This is gonna give me the
most consistent result for the large area that
I'm trying to track in. I'm gonna turn off the grid as well. So they're back to none
in layer properties. And I'm just gonna hide that shape here because I wanna show you another way of doing the same thing. I'm gonna come into my tool again. Remember, I'm still in the X plus here so I just wanna go to the X and all of our tools do this. So everyone has a little
plus symbol right next to it, if it adds to the layer rather
than creates a new layer, that's all of the tools. But I'm gonna create a new lay here because what I could do is
I could come into the plus. I can add in just multiple small shapes that give me good and
consistent tracking data. So let's see what happens when
I try and track this one in, let's do a similar thing
to our surface here. Just quickly bring that
into the right sort of area. There we go and turn on the grid. Just makes it easier to see, when we visualize these things, it just makes everything a lot easier. And I'll track that forwards and I'll track it backwards and I don't expect this
to be as successful. There we go, yeah. Which is sort of not exactly
what I was hoping for but completely understandable because I've got these smaller areas. There's not as much room for error as we would have with larger shapes. So you can see here, I've made this bottom
right-hand corner shape quite big and in fact, a lot
bigger than it needs to be. And then when the movement comes in, of the glass coming in there, obviously Mocha doesn't know
that that's a separate object. It thinks that that's something that it should be looking
at and it gets distracted. It goes, oh, there's a pretty,
pretty glass in a red dress. Let's do that. So what I'm trying to say here is when we are using smaller shapes, is we do want to come in and actually be a bit more careful with how much of excess
we have around the edge. We have a lot less latitude for mistakes when we're dealing with smaller shapes. So you see there, that's
tracking in a lot nicer and it's not getting as distracted when we're using small shapes
that are actually accurate. And that's looking pretty good. I mean, maybe not as good
as the one we had last time, I can see there's a
little bit of breathing. In the grid if we have a look there, as the light goes through, there's a little bit breathing. Sort of sucks up to the top
left-hand corner. [Sucks in] which isn't great, isn't what we want. So it's not as good as when we were working
with that shape there, those two strips but it
still gives a better result than we had when we were
tracking in the entire shape. And that's how we can use multiple shapes on a single layer to get better tracking. When we come back, we're gonna be looking at how
we can work with occlusions. So that's when objects
pass in front of the area that you want to be tracking. So join me in the next
part of exercise four, more tracking techniques.
