- [Instructor] In the last movie we saw how to change
the interpolation between key frames,
by choosing different interpolation types.
Now, we'll explore this a little bit more
to see how to customize interpolation
by manipulating tangent handles.
I've got the Curve Editor open with my camera selected.
If a selected key frame is of the type auto tangent
or spline, then it will display one or two lines
coming out from the key,
and those are the tangent handles.
An automatic tangent has a dashed blue line.
The ends of the tangents are boxes,
which are the handles to control the shape
of the interpolation.
If I want the transition out of a key frame
to happen more slowly,
I can lengthen the outgoing tangent handle.
For example, we can select the X position track,
and make sure that's framed with the Z key on the keyboard,
and we can select this first key frame it frames zero
and adjust the outgoing tangent handle length
by clicking and dragging.
And as soon as we do that it turns into a solid black line
indicating that it's no longer an auto tangent,
but it's a tangent of the type spline
also known as a basis spline.
A longer handle gives the slow out or ease out
a greater duration.
If we just click and drag,
we'll move that tangent handle both horizontally
and vertically.
We're changing the value and the time
that could be problematic in a case such as this
especially because if for example,
let's say I pan my view with the middle mouse
and I drag this tangent handles so that it is below
the key frame.
It has a lower value than the key frame.
And what we've done here is we've introduced
this negative slope.
The curve is going downward
and then going back upward again.
And we can observe this if we go to our top view
and rewind and play back our animation,
it's getting real close on the camera in the top view,
play back the animation,
and what you'll see is it moves a little bit to the left
or in negative X before it starts its journey
in the positive X direction.
And if we look at our camera view
we see that little hiccup.
All right, I'll stop that playback,
go back to the Curve Editor,
and I just want to undo those movements
that I made, Control + Z, do that a couple few times
until we're back to an auto tangent.
What we want to do here is we don't want to change the value
of the tangent in its vertical dimension,
we want to constrain our movement to only the time dimension
and that's done with the Control key.
Pull down the Control key, click and drag
and we're only changing the length of the handle.
We're not changing its value, so for example,
we could give this a little bit faster slow out,
set that to a duration of 40 frames.
Okay, we should do that for the other channels as well
in order to synchronize those channels
and give us a smooth motion.
Let's select the other channels here in our track list
hold down, Control, select the Y position,
hold down Control and select the Z rotation,
the blue Z rotation and then press the Z key
that'll frame all those curves.
If we select multiple key frames,
we'll see multiple tangent handles.
I'll select all these keys at frame zero
and now we see all their handles,
but they're all of different lengths.
If I want to edit multiple tangent handles,
it gets a little bit tricky.
By default we can only move one tangent handle at a time
because we can't actually select more than one tangent
handle at a time.
It can hold down Control and click and drag on this one
here, and it doesn't change the other tangent handles,
even though those key frames are selected.
But we can make that happen by enabling a feature called
Lock Tangents.
And that's found up here at the very extreme right
of the Curve Editor toolbar, we've got a section
that's called the Tangent Actions,
and there's a button on the extreme far right
with a padlock, Lock Tangents, enable that.
And now when you click and drag on a tangent handle
you will be able to manipulate the handles
for any other selected key frames.
Okay, well, that's good but you'll see here
that we're still maintaining the proportion
among the lengths of those various keys.
What we really want is for all those tangent lengths
to be the same.
And to do that they'll need to start out being the same.
I'll turn Lock Tangents off,
I'll drag them out so that they're all about the same length
holding down Control and dragging.
So now they all have a duration of 40 frames or so,
I can re enable Lock Tangents,
and now I can Control, click on any one of them
and manipulate all of their lengths.
So again, we'll set these all to have a duration
of about 40 frames.
And we can do a similar operation here
at the end of the animation,
we can change the slow in time for these keys,
drag a selection rectangle around those,
and we see again that they are all different lengths
even though they are auto tangents.
And the reason why this green Y position tangent
is shorter, is because this curve has three key frames
on it.
The other curves have only two keys.
The auto tangent length is proportional to the time
between keys.
So I'll set these all to the same length
once again, I'll turn Lock Tangents off.
And I just want to hold down Control and click and drag
on just the Y position tangent handle,
extend that out and bring that to be the same length
as the others, re-enable Lock Tangents,
and then with those three keys selected,
I can click and drag on any one of those
and scale them all at once,
let's make this a slower slow in.
We'll bring this out to a value of about frame 90
which will give us a slow in duration of about 60 frames.
Let's check our work, we'll rewind, playback,
see what we get in our view ports.
It's better, there's one more thing I think we can do
to put the finishing touches on this.
And that's just to flatten this exposition curve
make it a little bit less extreme there.
I'll select this key frame on frame 70,
and give it a value in the statistics field of negative 66
and press Enter, rewind and play that back.
And we've got a more gentle movement there.
All right that's the essentials of editing interpolation
with basis tangent handles in the Curve Editor.