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Game Development Projects with Unreal Engine
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Animation is essential for adding life and richness to a game. Superb animations are one of the major factors that differentiate average games from the good and the great from the best. Visual fidelity is what keeps gamers excited and immersed in games, and hence animations are a core part of all games and experiences created in Unreal Engine.
Note
This chapter seeks to cover animation basics. A more in-depth approach to animation will be taken in Chapter 13, Blend Spaces 1D, Key Bindings, and State Machines.
An Animation Blueprint is a specific kind of blueprint that allows you to control the animation of a Skeletal Mesh. It provides users with a graph specifically for animation-related tasks. Here, you can define the logic for computing the poses of a skeleton.
Note
A Skeletal Mesh is a skeleton-based mesh that has bones, all of which come together to give form to the mesh, whereas a Static Mesh (as the name suggests) is an un-animatable mesh. Skeletal Meshes are normally used for characters and life-like objects (for example, a player hero), whereas Static Meshes are used for basic or lifeless objects (for example, a wall).
Animation Blueprints provide two kinds of graphs: EventGraph
and AnimGraph
.
The Event Graph within an Animation Blueprint provides setup events related to animations, as we learned in Chapter 1, Unreal Engine Introduction, that can be used for variable manipulation and logic. Event graphs are mostly used within Animation Blueprints to update Blend Space values, which, in turn, drive the animations within AnimGraph
. The most common events that are used here are as follows:
Figure 2.22: Animation Event Graph
In the preceding screenshot, you can see the default Event Graph. There are Event Blueprint Update Animation
and Try Get Pawn Owner
nodes here. You created new nodes and appended them to a graph to complete some meaningful tasks in Exercise 2.04, Setting Up the Game Mode, Player Controller, and Pawn.
The Anim Graph is dedicated to and responsible for playing animations and outputting the final pose of the skeleton, on a per-frame basis. It provides developers with special nodes to execute different logic. For example, the Blend node takes in multiple inputs and is used to decide which input is currently being used in the execution. This decision is usually dependent on some external input (such as an alpha value).
The Anim Graph works by evaluating nodes by following the flow of execution between the exec pins on the nodes being used.
In the following screenshot, you can see a single Output Pose
node on the graph. This is the final pose output of the animation that will be visible on the relevant Skeletal Mesh within the game. We will be using this in Exercise 2.05, Creating a Mannequin Animation:
Figure 2.23: Animation AnimGraph
You have already learned how animation nodes and logic can be set up, but one essential component is missing. Who decides when a particular animation or piece of logic should play or execute? This is where State Machines come into the picture. For example, a player may need to shift from crouching to a standing pose, so the animation needs to be updated. The code will call the Animation Blueprint, access the State Machine, and let it know that the state of the animation needs to be changed, resulting in a smooth animation transition.
A State Machine consists of states and rules that can be thought of as depicting the state of an animation. A State Machine can always be in one state at a particular time. A transition from one state to another is carried out when certain conditions (which are defined by rules) are met.
Each Transition Rule contains a Boolean node by the name of Result
. If the Boolean is true, the transition can occur and vice versa:
Figure 2.24: Transition Rules
When you're provided with a bunch of animations, you can create a State Machine and run those animations. However, a problem is presented when you need to transition from one animation to another. If you simply switch the animation, it will glitch since the new animation's starting pose might be different from the old animation's ending pose.
Blend Spaces are special assets used to interpolate between different animations based on their alpha values. This, in turn, removes the glitch issue and interpolates between the two animations, causing a swift and smooth change in animation.
Blend Spaces are created either in one dimension, known as a Blend Space 1D, or two dimensions, known as a Blend Space. These blend any number of animations based on one or two input(s), respectively.
Now that you've gone through most of the concepts related to animations, we'll be diving in hands-on by adding some animation logic to the default mannequin. We'll be creating a Blend Space 1D, a State Machine, and Animation logic.
Our goal here is to create a running animation of our characters and thus gain insight into how animations work, as well as the way they are bound to the actual character in a 3D world.
The following steps will help you complete this exercise:
Chapter02
-> Exercise2.05
-> ExerciseFiles
directory, which can be found on GitHub. You can extract this to any directory you're comfortable with using on your machine.Note
The ExerciseFiles
directory can be found on GitHub at the following link: https://packt.live/32tIFGJ.
CharAnim.uproject
file to start the project.Play
. Use the keyboard's W, A, S, D keys to move and the Spacebar to jump. Notice that, currently, there are no animations on the mannequin.Content
folder, browse to Content
-> Mannequin
-> Animations
.Content
folder, and from the Animation
section, select Blend Space 1D
.UE4_Mannequin_Skeleton
.BS_IdleRun
.BS_IdleRun
to open it. Asset Details
tab, inside the Axis Settings
section, expand the Horizontal Axis
section and set Name
to Speed
and Maximum Axis Value
to 375.0
:Figure 2.25: Blend Space 1D Axis Settings
Sample Interpolation
section and set Target Weight Interpolation Speed Per Sec
to 5.0
.ThirdPersonIdle
, ThirdPersonWalk
, and ThirdPersonRun
animations into the graph separately:Figure 2.26: Blend Space previewer
Asset Details
tab, in Blend Samples
, set the following variable values:Figure 2.27: Blend Samples
Save
and close this Asset
.Content
folder, and from the Animation
section, select Animation Blueprint
.Target Skeleton
section, select UE4_Mannequin_Skeleton
and then click the OK
button:Figure 2.28: Creating the Animation Blueprint asset
Anim_Mannequin
and press Enter.Anim_Mannequin
file.Event Graph
tab.boolean
variable called IsInAir?
by clicking the +
icon in the variable section on the bottom left side. Be sure to assign the proper type:Figure 2.29: Adding variables
Speed
.Try Get Pawn Owner
return value node and type in Is Valid
. Select the bottom one:Figure 2.30: Event Graph Is Valid node
Exec
pin from the Event Blueprint Update Animation
node to the Is Valid
node:Figure 2.31: Connecting nodes
Try Get Pawn Owner
node, use the Get Movement Component
node. Is Falling
node and connect the Boolean return value to a set node for the Is in Air?
Boolean. Connect the SET
node exec pin with the Is Valid
exec pin:Figure 2.32: Is in Air Boolean setup
Try Get Pawn Owner
node, use the Get Velocity
node, get its VectorLength
, and connect the output to the A Variable Set
node of Speed
:Figure 2.33: Speed Boolean setup
Anim Graph
tab.AnimGraph
, type state machine
, and click on Add New State Machine
:Figure 2.34: The Add New State Machine option
MannequinStateMachine
.MannequinStateMachine
to the input pin for the Output Pose
node and click the compile button on the top bar:Figure 2.35: Configuring the State Machine result in the Output Pose node
MannequinstateMachine
node to enter the State Machine. You will see an Entry
node. The state that will be connected to it will become the default state of the mannequin. In this exercise, this will be our Idle Animation
.Add State
. Press F2 to rename it Idle/Run
.Entry
text, point it inside the Idle/Run
node, and then release it to connect it:Figure 2.36: Connecting Added State to Entry
Idle/Run
state to open it.Asset Browser
menu in the bottom-right corner, select and drag the BS_IdleRun
Animation onto the graph. Get the Speed
variable from the Variable
section on the left and connect it, as shown here:Figure 2.37: Idle/Run state setup
MannequinStateMachine
by clicking on its breadcrumb in the top banner:Figure 2.38: State Machine navigation breadcrumb
Asset Browser
menu, drag and drop the ThirdPersonJump_Start
Animation into the graph. Rename it Jump_Start
.ThirdPersonJump_Loop
and ThirdPerson_Jump
and rename them Jump_Loop
and Jump_End
, respectively:Figure 2.39: State setup
Jump_Start
state. Click on the Play ThirdPersonJump_Start
node. Uncheck Loop Animation
in the Settings
section.Jump_Loop
state and click on the Play ThirdPersonJump_Loop
node. Set Play Rate
to 0.75
.Jump_End
state and click on the Play ThirdPerson_Jump
node. Uncheck the Loop Animation
Boolean.Idle/Run
to Jump_Start
, drag from the Idle/Run
state and drop it to the Jump_Start
state. Similarly, Jump_Start
leads to Jump_Loop
, then to Jump_End
, and finally back to Idle/Run
. Drag and drop the arrows to set up the State Machine, as follows:
Figure 2.40: State connections
Idle/Run
to Jump_Start
transition rule icon and connect the output of the Is in Air?
variable to the result:Figure 2.41: Idle/Run to Jump_Start transition rule setup
Jump_Start
to Jump_Loop
transition rule. Get the Time Remaining (ratio)
node for ThirdPersonJump_Start
and check whether it is less than 0.1
. Connect the resulting bool to the result:Figure 2.42: Jump_Start to Jump_End transition rule setup
Jump_Loop
to Jump_End
transition rule. Connect the output of the inverse of the Is in Air?
variable to the result:Figure 2.43: Jump_Loop to Jump_End transition rule setup
Jump_End
to Idle/Run
transition rule. Get the Time Remaining (ratio)
node for ThirdPerson_Jump
and check whether it is less than 0.1
. Connect the resulting bool to the result:Figure 2.44: Jump_End to Idle/Run transition rule setup
Content
folder, browse to Content
-> ThirdPersonBP
-> Blueprints folder
and open the ThirdPersonCharacter
Blueprint.Mesh
in the Components
tab:Figure 2.45: Mesh component
Details
tab, set Anim Class
to the Animation Blueprint
class that you created:Figure 2.46: Specifying the Animation Blueprint in the Skeletal Mesh component
The following should be the output you achieve. As you can see, our character is running, and the running animation is being shown:
Figure 2.47: Character running animation
Note
You can find the complete exercise code files on GitHub, in the Chapter02
-> Exercise2.05
-> Ex2.05-Completed.rar
directory, at the following link: https://packt.live/3kdIlSL
After extracting the .rar
file, double-click the .uproject
file. You will see a prompt asking Would you like to rebuild now?
. Click Yes
on that prompt so that it can build the necessary intermediate files, after which it should open the project in Unreal Editor automatically.
By completing this exercise, you've understood how to create State Machines, a Blend Space 1D, the Animation Blueprint, and how to tie it all together with the Skeletal Mesh of a character. You've also worked on play rates, transitional speed and the transitional states, helping you understand how the world of animation intricately ties in together.
We kicked off this section by understanding how State Machines are used to represent and transition in-between Animation States. Next, we got to know how a Blend Space 1D gives us blending in-between those transitions. All this is used by the Animation Blueprint to decide what the current animation of the character is. Now, let's combine all these concepts together in an activity.
Let's say, as an Unreal games developer, you've been provided with a character skeletal mesh and its animations, and you've been tasked with integrating them inside a project. In order to do that, in this activity, you'll be creating an Animation Blueprint, State Machines, and a Blend Space 1D of a new character. By completing this activity, you should be able to work with animations in Unreal Engine and link them to skeletal meshes.
The activity project folder contains a Third Person Template project, along with a new character, Ganfault
.
Note
This character and its animations were downloaded from mixamo.com. These have been placed in the Content
-> Ganfault
folder on our GitHub repository: https://packt.live/35eCGrk
Mixamo.com is a website that sells 3D characters with animations and is sort of an asset marketplace only for 3D models. It also contains a library of free models, alongside the paid ones.
The following steps will help you complete this activity:
Content
-> ThirdPersonBP
-> Blueprints
and open the ThirdPersonCharacter
Blueprint.Details
tab on the right, replace the SkeletalMesh
reference with Ganfault
.Animations Blueprint
section of the skeletal mesh component with the Animation Blueprint you created for Ganfault
. Note
For the State Machine, implement only Idle/Run and Jump State.
Once you've completed this activity, the Walk/Run and Jump animations should be working properly, as shown in the following output:
Figure 2.48: Activity 2.01 expected output (Left: Run; Right: Jump)
Note
The solution to this activity can be found at: https://packt.live/338jEBx.
By completing this activity, you now know how to navigate your way around Unreal Engine with regard to the project, debugging code, and working with Animations. You also understand State Machines, which represent transitions between the Animation States and the Blend Spaces 1D used in that transition. You are now able to add animation to 3D models based on gameplay events and inputs.
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