2D animation

Two ways to 2D character animation

• Sprite sheet animation
  • Characters are drawn fully, and animated by hand, frame by frame
  • At best, results in lifelike and beautiful motion
  • At worst, the animator has to draw everything multiple times
  • Learn: Sprite Animation
• Skeletal animation
  • Characters consists of multiple images connected by bones
  • At best, varied procedural movement out of a few assets
  • At worst, stiff and unlifelike motion
  • Learn: Skeletal Animation

Sprite-based animation

• For sprite basics, see: 2d Basics: Sprite renderer component
• Sprite animation can be created with multiple individual png files, or one sprite sheet with multiple animation cels
• Brackeys video: 2D animation

Creating a new animation

• Manual: Creating a new Animation Clip
• Select the GameObject you want to animate
• Open Animation Window: Window > Animation > Animation
• Click Create to create a new animation (.anim) file, or a clip
  • An animation controller (.controller) gets created simultaneously as well
  • Also, your GameObject gets an Animator component
  • Name the first clip PlayerIdle
  • Good ideas to have separate animation files for Idle, Jump, Run, etc…

---

• Note: The functionality of the animation timeline above relies that you keep your GameObject selected
  • Otherwise, you can’t click the buttons
• Drag sprites to your Animation timeline
  • Note: The final frame duration is less than the others. For an easy fix, add a new key to the end with Right click > Add key
• Set Samples to a lower value to make your new animation less frantic
• You can create new clips in the PlayerIdle dropdown

Controlling animation with code

• The fastest way to get your animations running is to control the Animator component with code
• Script Reference: Animator.Play

  Animator anim = GetComponent<Animator>();
  anim.Play("PlayerAttack");
  

• Check which animation is playing

  if (anim.GetCurrentAnimatorStateInfo(0).IsName("PlayerAttack"))
  {
        Debug.Log("Playing attack anim!");
  }
  

Animator controller

• When you created new clips, an Animator Controller Asset was created
  • Manual: The Animator Controller Asset
• This can be modified in the Animator Controller Window
  • Manual: Animator Controller
  • Note: This was previously known as Mecanim State Machine
• To actually use the transition rules, your player GameObject needs the Animator component (it was added automatically)
  • Manual: Animator Component

Animator window

• Unity Animator window, aka the Animation State Machine can seem daunting if you’re not familiar with the concept of a State Machine
• Luckily, the Manual has good resources about state machines
  • Manual: State Machine Basics
• Note: the animator window can be janky. E.g., If you cannot move the states around, set the inspector into Debug mode
  • Inspector window > Three dots in the top right corner > Debug

Using the Animator window

• In Animator, we can create transition rules between animation clips
• Right click a state > Make Transition
• Entry is the default state: Create an arrow from it to the idle animation!
• Click on the arrow to edit the transition

Transitions

• Manual: Animation Transitions

• Has Exit time:
  • The most absolutely confusingly named variable of all years
  • Means: “Transition will happen automatically after Exit time has passed”
  • Usually we want to uncheck this.
• Settings
  • Exit time: The number of loops to go through before the automatic transition
    • Oh wow, it’s not even time, really
  • Transition Duration: In sprite animations, we usually want to set this to 0.

Animation parameters

• To trigger state transitions, we control the controller’s parameters in code
• Manual: Animation Parameters
• Change the Layers view to Parameters
• Create a new float parameter named Speed
• Go to a transition, and create a new condition for the parameter

  [SerializeField] Animator anim;
  
  anim.SetFloat("Speed",_rigidbody.velocity.Magnitude);
  

• anim.SetTrigger("StartWalking") works similarly

Animation clip properties

• We can control component properties straight from the animation clips themselves
• Use case: If we want to use the same walk animation sprites for PlayerWalkLeft that we have for PlayerWalkRight
• In the PlayerWalkLeft animation clip, click Add Property
  • Choose Sprite Renderer Component
  • Choose the FlipX property
  • Tick the box, and move the created key to the start of the clip

Blend trees

• Having animation states for all moving directions can lead to “transition hell”
• We can keep the base layer simpler by creating blend trees: Manual: Blend trees
• A common usage for blend trees is to add directional animation:
  • E.g., a PlayerWalk blend tree that contains PlayerWalkDown, PlayerWalkUp, etc states
  • Create a blend tree by right-clicking the animator background and choose
    • Create state > From new blend tree
  • Name the blend tree to PlayerWalk, and double click the blend tree to open it
• Note: You can also convert an existing state into a blend tree with Right click > Create blend tree from state

Creating a 2D blend tree

• Change Blend type to 2D Simple directional.
• Set two float parameters to control the blend tree (here: XSpeed and YSpeed)
  • Create the parameters if you need to.
• Press + to add four empty Motion fields (a.k.a., slots for the animation clips) to the blend tree

---

Adding animation clips to a blend tree

• Drag the animation clips from the Project view to motion fields
• Set the Pos X and Pos Y parameters or drag the motion fields to their corresponding positions (PlayerWalkDown should be down, etc.)
  • Values of 0.1 seem to work well so the states are triggered even when the analog stick is moved slightly. See image in the previous slide!
• Now, when you change the values of the parameters XSpeed and YSpeed, the blend tree will go to the motion field that matches the values the best

Animation controller example

displacement = new Vector2(Input.GetAxis("Horizontal"), Input.GetAxis("Vertical"));
displacement = Vector2.ClampMagnitude(displacement, 1);
rb.velocity = displacement * Time.deltaTime * walkSpeed;

animator.SetFloat("WalkSpeed", rb.velocity.magnitude);

if (displacement.magnitude > 0.1f)
{
    animator.SetFloat("XSpeed", displacement.x);
    animator.SetFloat("YSpeed", displacement.y);
}

• Here, we set three properties:
• WalkSpeed is used to transition between PlayerIdle and PlayerWalk blend trees
• XSpeed and YSpeed are used to choose direction in the blend trees
  • Note that we don’t reset them when movement stops!

Controlling animation clip speed

• You can control the speed an animation clip is played easily by setting a parameter to control it
• Click on a state in the animator to show it in the inspector
  • Check Parameter under Speed
  • Choose the float parameter you want to use as a multiplier for the animation clip speed
  • Done!

Extra: Animation Events

• Manual: Using Animation Events
• You can add animation events to call a function in a specific point of an animation

Extra: State machine behaviour scripts

• Manual: State Machine Behaviours
• To add functionality to animation states, you can add state machine behaviours

Extra: UI animations

• Packages: Unity UI: Animation integration

Extras

• 9-Slicing
  • Manual: 9-Slicing your Sprite
• Sprite Masks
  • Manual: Sprite masks
• Sprite Creator
  • For creating (placeholder) sprite graphics
  • Assets > Create > Sprites
  • Manual: Sprite Creator

Extras: Pixel art in Unity

• Sprite import:
  • Texture type: Sprite (2D and UI)
  • Pixels Per Unit: Tile size (e.g., 32)
  • Filter Mode: Point (No filter)
  • Compression: None
• Edit > Project Settings > Quality > Anti-aliasing: Disabled

---

• Preparing for pixelart
  • Unity pixel art tips
  • Making your Pixel Art Game look Pixel Perfect in Unity3D
• Pixel perfect camera
  • Packages: Pixel perfect camera
  • Many issues can be fixed by using a pixel perfect camera instead of a basic camera
  • For instance, you can crop the play area to represent a low resolution display
  • This can also be used for uniformly scaling the pixels by an integer amount
• Note: If you still see black gaps in your tilemaps after following these instructions, create a new material with the Sprites/Default shader and check Pixel snap. Then, add this material to every Tilemap renderer.

Learning

• Top-down movement with animation
  • Top-down movement in Unity
  • Brackeys video: Top down movement
• Madwomb: Basics of Unity 2D
• Madwomb: Mecanim - Animation Controllers and State Machines