General

• Introduction
• Frequently Asked Questions
• Roadmap
• Release notes

Basics

• Getting Started
  • Install JDK
  • Set Up IDE
  • Build Systems
  • Project Structure
  • Get LITIENGINE
  • Manage native libraries
  • Run the Game
• Game API
  • Game.graphics()
  • Game.audio()
  • Game.physics()
  • Game.loop()
  • Game.tweens()
  • Game.world()
  • Game.window()
  • Game.screens()
• Input API
  • Input.keyboard()
  • Input.mouse()
  • Input.gamepads()
• Configuration
• Tile Maps
  • Map Objects
  • Custom Properties
• Resource Management
  • Texture Atlas
  • Sprite Info Files
• Entity Framework
  • Default Entity Types
  • Props
  • Subscribe to Entity Events
  • Annotations for static information
• Control Entities
  • Entity Controllers
  • Animation Controller
  • Movement Controller
  • Behavior Controller
  • Messaging System
  • Ability Framework
• User Interface
  • GuiComponents: An Overview
  • Creating Menus
• utiLITI
  • Create Projects
  • Import maps
• Deployment
• Savegames
• Libraries and Tools

Tutorials

• Creating a Simple Platformer
• Creating an Arkanoid Clone
• Modifying example projects

Tweening

The tweening framework is a powerful tool that allows you to animate properties of different types of objects in your game. It is a simple way to create smooth interpolations, e.g. for position, size, rotation, opacity, and more.

The Tweening Engine - Game.tweens()

The tweening engine is a part of the Game object and can be accessed via Game.tweens(). It is a singleton manager for all the Tween instances in the game. The engine is responsible for updating all the active Tweens in the game, and it provides methods for creating, pausing, resuming, and stopping Tweens. A Tween is an object that interpolates a value over time, using a specified easing function to create smooth transitions. You can instantiate a Tween by calling the Game.tweens().begin() method and passing the target object, the type of value to interpolate, and the duration of the tween. Then you can chain methods to set the starting and ending values, the easing function, and any additional properties.

ImageComponent ic;
// Create a new Tween that moves the ImageComponent to the given location over 4 seconds, using a quadratic easing function.
Game.tweens().begin(ic, TweenType.LOCATION_XY, 4000)
    .target(100, 200)
    .ease(TweenFunction.QUAD_INOUT)
    .begin();

TweenType

The TweenType enum defines the types of values that can be interpolated. Some examples include:

• ANGLE: Interpolates the angle of an object.
• COLLISION_BOTH: Interpolates both the width and height of the collision box.
• COLLISION_HEIGHT: Interpolates the height of the collision box.
• COLLISION_WIDTH: Interpolates the width of the collision box.
• HITPOINTS: Interpolates the hitpoints of a Combat Entity.
• LOCATION_X: Interpolates the X-coordinate of an object's location.
• LOCATION_XY: Interpolates the X- and Y-coordinate of an object's location.
• LOCATION_XY: Interpolates the Y-coordinate of an object's location.
• SIZE_BOTH: Interpolates both the width and height of an object.
• SIZE_HEIGHT: Interpolates the height of an object.
• SIZE_WIDTH: Interpolates the width of an object.
• VELOCITY: Interpolates the velocity of an object.
• VOLUME: Interpolates the volume of a Sound source.
• FONTSIZE: Interpolates the font size on GUI components.
• OPACITY: Interpolates the opacity of an object.

Note that not all types are supported by all objects. For example, the VOLUME type is supported by VolumeControl, but not by GuiComponent. To see which types are supported by a specific object, refer to the API documentation and the specific Tweenable's implementation of getTweenValues and setTweenValues.

TweenFunction

We have two ways of instatiating a TweenFunction: You can either call the TweenFunction enum to use one of our many pre-implemted Tween functions, or create a custom TweenFunction by implementing a function that takes the progressed time as input and returns the modified Tween value as output. The premade Tween functions are based on Robert Penner's easing equations, which are mathematical formulas that create smooth transitions.

Each enum constant represents a different easing function and is associated with a TweenEquation lambda expression that computes the easing value based on the input time.

• The LINEAR function simply returns the input time, creating a linear transition.
• The QUAD_IN function represents a quadratic easing-in function, which accelerates from zero velocity. Similarly, QUAD_OUT and QUAD_INOUT provide quadratic easing-out and easing-in-out transitions, respectively. The QUAD_OUT function decelerates to zero velocity, while QUAD_INOUT combines both behaviors.
• The CIRCLE_IN, CIRCLE_OUT, and CIRCLE_INOUT functions use circular equations to create easing effects that mimic the motion of a circle.
• The SINE_IN, SINE_OUT, and SINE_INOUT functions use sine wave equations to create smooth sinusoidal transitions.
• The EXPO_IN, EXPO_OUT, and EXPO_INOUT functions use exponential equations to create transitions that start or end very quickly.
• The BACK_IN, BACK_OUT, and BACK_INOUT functions create transitions that overshoot their target value before settling.
• The BOUNCE_OUT, BOUNCE_IN, and BOUNCE_INOUT functions simulate a bouncing effect, where the value bounces back and forth before settling.
• Finally, the ELASTIC_IN, ELASTIC_OUT, and ELASTIC_INOUT functions create elastic transitions that oscillate before settling.

Each easing function is implemented as a lambda expression that takes a float time parameter (ranging from 0 to 1) and returns a float value representing the eased progress. The compute method in the TweenFunction calls the associated lambda to calculate the eased value for a given time.

---

Last updated 4 months ago

On this page