of two or more animations.

For example if you have animations

for running left, running forward

and running right you might want animations

for running only slightly to the left or right.

Another common example is having

walking and running animations

but wanting the character to be able to move

at different speeds between the two.

Blend trees can be used to achieve this.

To create a blend tree right-click on empty space

in the animator window.

Choose Create State - From New Blend Tree.

This creates a state that has a blend tree

as it's motion instead of a single animation.

Double clicking on the state allows you to

edit the blend tree.

The breadcrumb in the upper left hand corner

shows us that we are working in our blend tree.

Clicking the base layer name will bring us

back out of the blend tree.

With the blend tree selected we can see it's

properties in the Inspector.

The first thing to note is that

blend tree's have names.

These can be different from the state

that holds them.

Next comes the blend type.

For now we will be concentrating on

one dimensional blend trees.

We will be coming back to the different types

of 2 dimensional blend trees later.

One dimensional blend trees use a single

parameter to control how much of each

of it's motions should be played.

In the example given earlier of

running left or right the blend tree's

parameter might be something like

direction or angular speed.

Or for the walking/running example

the parameter could be speed.

Next is the list of motions.

To add motions click the + icon.

This gives you the options of Ad Motion Field,

and New Blend Tree.

Selecting New Blend Tree

allows you to have nested blend trees

so you can blend animations

based on more than one parameter.

However, if you wish to do this

an easier approach is usually

to use 2 dimensional blend trees.

As such we'll be dealing with

just adding motion fields.

Each motion field represents an animation.

These can be dragged on from the Assets

in the Project panel or selected from a list

by using the circle select button.

Each motion field then has 3 properties.

The threshold is the value of the

parameter you have selected

that represents a blend using entirely this animation.

For example, let's say you have a walking

and running animation and their thresholds

are 5 and 10 respectively.

If the Speed parameter is set to 10

then the blend tree will play just

the running animation.

If it's set to 7.5 it will play a 50/50 blend

of walking and running.

The next property is the Time Scale.

This affects the speed the animation is played at

just the same as the speed property

for normal states.

The last property decides whether or not

the animation is mirrored left to right.

After adding motion fields you'll notice that a

blue cross pattern diagram appears

above the list of motions.

This is an illustration of where the different

motions lay on the scale of the parameter.

The lowest threshold on the left,

the highest on the right.

You can use the red scrubber to preview the

blended animation for various values.

If you wish to change the order of the motions

on a blend tree for any reason

you can drag the motions around using

the handle on the left of the motion property.

Below the list of motions are a few properties

that help adjust the attributes of your motions.

Generally it's a good idea to use these options

once you have added all of the motion

fields you need and given them animations.

If Automate Thresholds is checked

then the thresholds you have for each

animation will be set and won't be changeable.

If it is unchecked then we can use

the following 2 options.

Compute Thresholds will calculate

and set values for the thresholds of each

of your motion fields.

It will do this based on a property of

root motion, which you select.

These properties are Speed, Velocity X,

Velocity Y, Velocity Z

and Angular Speed in either radians

or degrees.

Since blend trees often have their thresholds

based on these root motion properties

these are also common examples

of animator parameters.

Using Adjust Time Scale

you can make the speed for each animation

homogenous.

This means that each of the animations

will result in the same speed of root motion.

2 dimensional blend trees work in a very

similar way to 1 dimensional blend trees

but blend according to 2 parameters

instead of 1.

There are 3 types of 2D blend trees.

The first 2 are for blending based on direction.

They are 2D Simple Directional

and 2D Freeform Directional.

The last type is 2D Freeform Cartesian

and it is used for situations where the

parameters do not represent direction.

2D Simple Directional is used for

when you want to blend movement based

on directional parameters and have single

animations on each direction,

such as walk forward, walk back, walk left, etcetera.

2D Freeform Directional is used similarly

but can include multiple animations

in the same direction.

For example walk forward and run forward.

2D Freeform Cartesian is used when the

parameters are not based on direction,

for example speed and angular speed.

Creating each of these types of blend trees

works the same.

Once you have chosen a type

choose an animator parameter to represent

the X axis and one to represent the Y axis.

For the directional types a standard

X axis parameter might be velocity X.

And a standard Y axis parameter might be

velocity Z.

For Freeform Cartesian

this choice is more open.

Once you have chosen your parameters the next step

is to add motions.

Just as with 2D blend trees

these can be either blend trees or motion fields.

However unlike 1D blend trees

the order in which they are added doesn't matter.

Once you have added motions you will see a

diagram of where the motions are

according to their thresholds.

This again works the same as

1D blend trees, but since it is based on

2 thresholds, an X threshold and a Y threshold

the diagram is in 2 dimensions.

Each of the motions can be positioned manually

by dragging them on the diagram

positioned by setting the thresholds manually

or by using the Computer Positions option.

This works the same as the Compute Thresholds

option for 1D blend trees but computes the

threshold based on both parameters.

1 dimensional blend trees use a red scrubber

to preview the motion.

For 2D blend trees there is a red dot

that can be dragged around.