Animation
The Animation class contains the info on the key frames of the what is to be animated. All this class holds are the list of key frames, the list of indices associated to each key frame in the order to be palyed back in, as well as a list of Duration frame times for the amount of time spent displaying each frame.
The Animation<T> class also expects a type parameter. This would usually be a TextureSlice but we can pass in any type we want to animate. For the following examples, we will be using a TextureSlice.
The Animation class itself doesn’t handle any of the playback or playback times. We have to pass in the time expired to the class for it to determine which key frame is to be played. We can use an AnimationPlayer to enable playback of an animation but it is not required.
And of course we can create our own instance of an animation by simply just passing in the list of frames, indices, and times without needing an atlas.
Creating an animation from a TextureAtlas
We can easily create an animation from a TextureAtlas by doing the following below. See Texture Atlas on more info on how to use a TextureAtlas.
val atlas: TextureAtlas = resourcesVfs["tiles.atlas.json"].readAtlas()
val heroRun: Animation<TextureSlice> = atlas.getAnimation("heroRun")
We can also create our own animation based off the frames from an animation, we can do the following:
val atlas: TextureAtlas = resourcesVfs["tiles.atlas.json"].readAtlas()
val heroRun: Animation<TextureSlice> = atlas.createAnimation("heroRun") {
frames(indices = 0..2, frameTime = 150.milliseconds)
frames(index = 3, frameTime = 300.milliseconds)
frames(indices = 0..2, frameTime = 150.milliseconds)
frames(indices = 4..5) // defaults to 100.millseconds
}
This creates an animation with frames of differing display times in the order of [0, 1, 2, 3, 0, 1, 2, 4, 5] instead of the default order of 1-5 at 100.millseconds.
Playback
What good is an animation if we can’t play it back? Fortunately, we can use the AnimationPlayer for that.
Creating an AnimationPlayer expects a type parameter as well. This needs to match the type parameter of the Animation that needs played back.
Using an AnimationPlayer
Playing an animation in a loop:
val batch = SpriteBatch(this)
val viewport = ExtendViewport(480, 270)
val camera = viewport.camera
val atlas: TextureAtlas = resourcesVfs["tiles.atlas.json"].readAtlas()
val heroRun: Animation<TextureSlice> = atlas.getAnimation("heroRun")
val anim = AnimaationPlayer<TextureSlice>()
anim.playLooped(heroRun)
onRender { dt ->
gl.clear(ClearBufferMask.COLOR_BUFFER_BIT)
anim.update(dt) // handles requesting the next frames in the current animation
camera.update()
batch.use(camera.viewProjection) { batch ->
anim.currentKeyFrame?.let { // use the current key frame of the animation to render
batch.draw(it, 50f, 50f, scaleX = 5f, scaleY = 5f)
}
}
}
Playing an animation a specific amount of times:
val batch = SpriteBatch(this)
val viewport = ExtendViewport(480, 270)
val camera = viewport.camera
val atlas: TextureAtlas = resourcesVfs["tiles.atlas.json"].readAtlas()
val heroRun: Animation<TextureSlice> = atlas.getAnimation("heroRun")
val heroIdle: Animation<TextureSlice> = atlas.getAnimation("heroIdle")
val anim = AnimaationPlayer<TextureSlice>()
anim.playOnce(heroIdle) // stops after one play through
anim.play(heroIdle, times = 5) // stops after 5 play throughs
onRender { dt ->
gl.clear(ClearBufferMask.COLOR_BUFFER_BIT)
anim.update(dt)
camera.update()
batch.use(camera.viewProjection) { batch ->
anim.currentKeyFrame?.let {
batch.draw(it, 50f, 50f, scaleX = 5f, scaleY = 5f)
}
}
}
Performing an action on a specific frame of an animation:
val atlas: TextureAtlas = resourcesVfs["tiles.atlas.json"].readAtlas()
val heroRun: Animation<TextureSlice> = atlas.getAnimation("heroRun")
val anim = AnimaationPlayer<TextureSlice>().apply {
onFrameChange = { index ->
if (index == 2) {
// do something
}
}
}
Stopping an animiation:
val atlas: TextureAtlas = resourcesVfs["tiles.atlas.json"].readAtlas()
val heroRun: Animation<TextureSlice> = atlas.getAnimation("heroRun")
val anim = AnimaationPlayer<TextureSlice>()
anim.playLooped(heroRun)
// ...
anim.stop() // stops the current animation from playing
Registering Animation States
Instead of having to handle playing animations manually we can register a state with a predicate that will automatically trigger the animation to play. Each state has a priority as well as a predicate that needs to return true in order to trigger. An animation with a higher priority will play over an animation with a lower priority.
val batch = SpriteBatch(this)
val viewport = ExtendViewport(480, 270)
val camera = viewport.camera
val atlas: TextureAtlas = resourcesVfs["tiles.atlas.json"].readAtlas()
val anim = AnimationPlayer<TextureSlice>()
val atlas = resourcesVfs["tiles.atlas.json"].readAtlas()
val heroSleep = atlas.getAnimation("heroSleeping")
val heroSlingShot = atlas.getAnimation("heroSlingShot")
val heroIdle = atlas.getAnimation("heroIdle", 250.milliseconds)
val heroWakeup = atlas.getAnimation("heroWakeUp")
val heroRun = atlas.getAnimation("heroRun")
val heroRoll = atlas.getAnimation("heroRoll", 250.milliseconds)
var shouldSleep = false
var shouldWakeup = false
var shouldRun = false
var shouldRoll = false
anim.apply {
// register all the animation states here.
registerState(heroRoll, 11) { shouldRoll }
registerState(heroWakeup, 10) { shouldWakeup }
registerState(heroRun, 5) { shouldRun }
registerState(heroSleep, 5) { shouldSleep }
registerState(heroIdle, 0) // returns true by default.
}
onRender { dt ->
gl.clearColor(Color.CLEAR)
gl.clear(ClearBufferMask.COLOR_BUFFER_BIT)
if (input.isKeyJustPressed(Key.NUM1)) {
shouldSleep = !shouldSleep
}
if (input.isKeyJustPressed(Key.NUM2)) {
shouldWakeup = !shouldWakeup
}
if (input.isKeyJustPressed(Key.NUM3)) {
shouldRun = !shouldRun
}
if (input.isKeyJustPressed(Key.NUM4)) {
shouldRoll = !shouldRoll
}
if (input.isKeyJustPressed(Key.ENTER)) {
// we can play an animation over any current animation state
anim.play(heroSlingShot)
}
if(input.isKeyJustPressed(Key.SPACE)) {
// we can play an animation over any current animation state
anim.play(heroRoll, 2.seconds)
}
anim.update(dt)
camera.update()
batch.use(camera.viewProjection) { batch ->
anim.currentKeyFrame?.let {
batch.draw(it, 50f, 50f, scaleX = 5f, scaleY = 5f)
}
}
}