Original subtitles

- [Instructor] In this video,

we will see how to use a curve as a path

as in the tree climbing sequence.

In the corresponding file,

I have two collections, one including a simple arrow

and the other one including our squirrel character

and the tree.

Getting back to the arrow collection,

I will press Shift + A

to add a curve, Bezier curve.

As any other object added to your scene,

it is spawned onto the 3D cursor.

It has an origin point

and if I press Tab to enter edit mode,

I can access the handles of the curve.

It's pretty close to the handles we have

in the graph editor.

Curves have an orientation,

meaning that they have a starting point

and an ending point.

To see it, we can go into the overlay

and display the normals of the curve.

Arrows will be displayed along the curve,

showing you the orientation of flow

of the curve, also called normals of the curve.

In edit mode, you can manipulate the handles,

as I explained before,

using G, R and S.

You can change the handle type

as you will do in the graph editor,

pressing the V key.

Then you will get the same behavior

as the one we have in the graph editor

but this time for a 3D object.

And with any curve point selected,

you can press E to extrude a new point.

As any object, we can access the curve

that are in the properties panel.

You can give a bit of thickness

or geometry to your curve going into the geometry panel.

The simple extrude will generate a rebound-like shape,

while the bevel will allow you

to create some kind of pipe.

While we don't need geometry for animation,

it makes the curve more readable in the 3D space.

In object mode, I can select my arrow object,

then select the curve to make it active.

Press Control + P and choose Follow Path.

Now if I scrub into the timeline,

I can see the arrow following the curve.

In the path animation option of the curve,

we can see the value frames.

And it is set to 100 frames.

It means that the object

that is parented to the curve

with the follow path option

will take 100 frames to get

from the beginning of the curve 'til the end of the curve.

Switching to 50 frame value,

you can see that now my arrow get to the end

of the curve on frame 50.

As our arrow object is currently a child

of the curve, we can move it at will.

It will still follow the path.

And we can see that by default,

our arrow object will rotate

to follow the curvature of the path.

If I go into the option of the curve

to the path animation and uncheck Follow,

the object is no longer rotating

to follow the orientation of the curve.

The curve path only affect the location of the object.

Let's restart from scratch.

I have removed any influence from the curve.

I will reselect the arrow,

then the curve, press Control + P

and this time, choose Path Constraint.

This will add a path constraint to the arrow

that we can see in the Constraint tab

of the properties editor.

From there, if I scrub into the timeline, nothing happened.

Our object gets stuck on the initial point

of the curve.

If I click the Animate Path button,

now our object is traveling along the curve

and you can see that it takes it 100 frames

to follow the curve, as before.

It still use the frame's value

from the curve properties.

Let's go back onto our arrow object

and check out the constraint.

We can see the forward axis and up axis option.

To better understand it,

I will display the axis on my object.

So we can see that our arrow

is pointing in its y direction

and the up axis is the z-axis,

exactly as set into the constraint.

So if I now click the Follow Curve option,

the orientation of the arrow will change.

It will follow the curve.

Its y-axis will be aligned with the curve path

and the z-axis will still be pointing up

as set in the constraint.

If I switch the orientation to -y,

it will flip the arrow but it will still follow the curve

and so if I choose the x-axis, for example,

logically you can't use the same channel

as a forward and up axis.

It will deactivate the constraint

and it will no longer work.

The offset value have two different behavior.

Let's move to frame 20

and in the offset value, set the value to 10.

Our arrow is moved back on the curve.

Its current position is frame 20, -10 frames.

The offset value is how we delay the position

of the arrow in time.

Basically, we are subtracting the offset value

to the frame's value of the curve.

So if I set it to -10,

it will currently move the arrow forward,

10 frame earlier in time.

Exactly as if I was on frame 30 without any offset.

If I now enable the fixed position,

our arrow object will be stuck

to the beginning of the curve.

Now the offset value is no longer a value in frame

but a value that goes from zero to one

and indicate the position

between the beginning and the end of the curve.

Finally, if I enable the curve radius option,

our constraint object scale

will depend on the curve radius.

So if I now go into edit mode

onto the curve and press Alt + S

with one of the control points selected,

I will be able to change the radius of the curve

and this will influence the scale

of our arrow objects.

Finally, in edit mode,

when working on the curve,

with a control point selected,

I can change the tilt value

and I will see my curve twisting or tilting.

And so will the object

that is constrained by the curve,

creating very nice animations.

We can tilt the curve with the Control + T shortcut.

Let's now see how we can use this trick

to animate our squirrel character.

I will display the squirrel collection.

I will move the current curve into the arrow collection

and I will press the Shift + A in object mode

to add a new curve.

This is going to be our squirrel path.

This time, instead of constraining the squirrel object,

I will constrain the root bone of our character.

In pose mode, I can go to the bone constraint,

not the object constraint

and add a follow path constraint

and source our curve.

Now the root bone of our character gets stuck

at the beginning of the curve.

If I click the Follow Curve option,

I can see my character getting align with the curve

and if I now scrub, I can't see it moving

because we need to click the Animate Path button.

And by default, our character

will follow the curve and reach the end on frame 100.

To give a proper orientation to our character,

we need to switch to -y as being the forward axis.

Now our character is properly following the path.

A big warning here.

Whenever you are using a curve modifier,

make sure that the constraint object

has its origin aligned with world space,

meaning that its origin is reset

because if you offset the object,

the constraint will behave weirdly.

You can move the curve as you want.

The constraint object will follow

but make sure that the constraint object

has all its transform channels reset.

Now that you understand the curve constraint,

you can go into edit mode

and start building your motion path

for your character.

I'm doing it into a little time lapse

because I'm using a simple rotation scale

and extrude functions.

My main advice is use as less point as possible

and try to have your curve as smooth as possible.

Also, you can use the bevel option

to give a bit of thickness to your curve

so that it's easier to read along the tree trunk.

The less control point you set onto your curve,

the easier it will be to keep it smooth

and so the animation of your character

will also be smooth.

If you create hard angles or too curvy path,

then the animation of your character

will look weird unless you heavily edit the animation

on top of the cycle.

When you're satisfied with the path,

you can zoom in and tweak the tilt and position

of the control point

so that your character feet stick to the trunk

and you avoid the clipping.

Don't forget to double check from camera view

because sometimes, even if your character

is a bit floating, that's perfectly fine,

'til it looks good from the camera point of view as usual.

Back to object mode,

we need to set the correct speed

for our character to climb the tree

and we can do it by modifying the frame's value

into the curve's option.

As the feet are moving backward,

it means that our character animation

is faster than the locomotion.

So I need to reduce the frame's value.

With a value of 70, it seems that now the feet

are sliding forward.

So our character locomotion is too fast.

So it's just a matter of trial and error

to find the correct value.

A value of 85 seems to work well for me.

And it depends on the curve length.

So you may not have the same value.

Another way to control the speed

at which our character is moving

is to use the offset.

We can enable the fixed position.

Now our character is no longer moving

and insert a keyframe on the offset factor.

I'm setting a value of zero on frame zero

and on frame 85, a value of one.

If I now go into the graph editor,

I will be able to see the curve

of this animated value

and we can see that there is easing in

and easing out,

so our character is slowing down and accelerating.

What I do need to do

is whether change the interpolation of the curve

to linear or select all the handles,

press V, and switch to vector.

The cool thing about choosing this method

is that I can insert a keyframe

whenever my character is about to jump.

Then another keyframe when he's just landing

and then I can offset a bit the landing keyframe

if I want my character to make a larger jump.

The only thing not to forget

is to also offset the latest keyframe

so that the interpolation between those two keyframe

doesn't change, and so our character speed remain the same.

But between frame 22 and frame 29 here,

the speed of my character is no longer the same

and it seems he's doing a bigger jump.

This is a little trick that will allow you

to break the rhythm of your animation

and make it more appealing.

At least, less linear.

This is the end of this chapter.

You now know everything to be able

to create the same shot as I did.

Don't forget that failing is a part of the process

but giving up is not a part of the process.

Stay strong, repeat

and I will see you in the next chapter

where we will learn new animation techniques.

To summarize, we have seen that we can use a 3D curve

as an animated path for an object to follow.

We can use parenting or path constraint.

The frames' value determines the time

to travel along the whole curve.

We can use the offset value to delay the path animation.

We can use the curve to scale

and tilt the constrained object.

We can use the constraint on a bone.

Make sure the origin of the constrained object

is reset to world origin

before applying the curve constraint.