- [Man] A free camera that has no target,
behaves more like a camera in the real world.
And whether it's a physical or a standard free camera,
we'll need to take a couple extra steps,
in order to make that camera operate,
like it's on a tripod.
Because by default, that's not going to be the case.
Additionally, unless you take these extra steps,
you might encounter some serious issues,
especially around animation.
Let's demonstrate.
If I select this free physical camera,
and go to the rotate tool,
my default will be in view coordinate system,
which is essentially the world coordinate system.
And I can rotate that around the world Z axis,
either in the top view or over in the perspective view.
We'll see that we're able to pan that camera.
And that's fine. No issues there.
The problems come when we try to rotate,
in view coordinate system in any other axis.
So if I try to rotate around the Y axis,
go over here, right click and click on the Y axis.
Okay, I'm introducing what's called a Dutch tilt,
or a canted angle.
Okay. I don't want that.
So I'll undo that with control Z.
Let's say I wanted just a tilt.
And if my camera is not aligned with the world,
and I try to tilt around the X axis in this case,
immediately again I get that canted angle or Dutch tilt.
So, view coordinate system is really no good at all.
So, I'll undo that with control Z.
Most people encountering this issue,
would just immediately switch to local coordinate system.
Switch our reference to local.
And now the rotate gizmo is aligned with the camera itself.
So now if we go over to our perspective view,
and drag on that X axis, we're able to tilt up and down.
Undo that with control Z.
Or pan by clicking on the Y axis,
which is the green axis in this case.
And we see, we don't have any problem there.
That looks good too.
The problem comes when we try to both pan and tilt.
Let's say, I tilt down.
Maybe move my camera up,
just so we can see this a little bit better.
So I tilt it down and then go back to my rotate tool.
And then I try to pan by rotating around the Y axis,
of the local coordinate system.
And you know what, immediately, I get a Dutch tilt again.
And not just panning,
but I'm actually introducing that canted angle,
at the same time.
Okay, so I'll undo that a couple times. Control Z.
Go back to where I was with this neutral framing.
The takeaway here is that we can't combine pan and tilt,
using the local coordinate system.
Pan rotation around the local Y axis is fine,
as long as there's no tilt and vice versa.
But that's a really unacceptable limitation.
We need to combine pan and tilt.
One possible solution to this,
might be to choose different reference coordinate systems,
for different rotation axes.
So for example, rotating around the local axis for tilt,
seems to work just fine.
So let's say I tilt up a little bit,
and if I want to pan,
I can switch the reference coordinate system to view,
or even world, which is more explicit.
And then I can rotate around the world's Z axis.
You can do that in the perspective view or any view.
Now we've combined panning and tilting.
But I need to switch back and forth.
If I want to tilt I have to go back into local and then tilt.
And then if I want to go back to panning,
I have to switch back to world.
So this isn't really optimal.
It's kind of a waste of time to have to do that every time.
And really additionally, and more importantly,
this will cause problems with animation.
Animated rotations will not behave predictably.
The object will spin around in some crazy direction.
You'll have no control.
The solution is just don't use local or world mode.
Use the gimbal coordinate system. Switch over to gimbal.
So in this mode, the X axis is still tilt,
and the Z axis is still pan.
But we're not panning around the world,
and we're not tilting relative to the world.
We're actually manipulating relative to the object itself,
but it's a more accurate version of that,
then we would see with a local coordinate system.
Because local mode is actually fake.
It's a temporary reference frame,
that is aligned with the object pivot.
Local mode does not accurately represent,
the complex interactions of the rotational axes themselves.
We'll talk about this more in the next movie.
But for now, it's enough to know that gimbal mode,
will prevent those problems that we saw in local mode.
It just so happens that, by default,
gimbal mode works fine for a camera.
As long as that camera does not have a Dutch tilt.
So we can rotate around gimbal Z to pan.
We can rotate around gimbal X in order to tilt.
If we rotate around gimbal Y, we'll introduce a Dutch tilt.
Maybe we want that. Maybe we're doing a horror film.
So it's not really a problem in this case,
it's an aesthetic choice.
But then if we try to tilt up and down,
we are tilting around an axis,
that's not actually orthogonal to the world.
So this is kind of a subtle distinction here.
But it's more obvious if we do a Dutch tilt,
that's really extreme.
If we bring this all the way over to 90 degrees,
then we actually achieve a situation that's very bad,
called gimbal lock.
And now we have two axes superimposed over one another,
and this severely limits our ability,
to control what we're doing.
So we don't want that.
So gimbal mode is pretty good.
It gets us most of the way there.
But if we want full control over the camera,
and not have any issues, then we're going to want to set,
the priority of rotational axes,
to emulate the mechanics of a tripod.
We'll take a look at that in the following movie.
For now, that's the importance of using gimbal mode,
for rotations of a free camera.