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  • 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.

Sometimes when animating you want a mix

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B1 UK blend parameter motion tree animation directional

Blend Trees - Unity Official Tutorials

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    朱瑛 posted on 2014/05/02
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