Sometimes when animating you want a mix
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.
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