Animation

jEngine animates in three ways: sprite sheet animations, property tweens and skeletons.

Sprite Sheet Animations

Attach a SpriteAnimator component with named clips. Each clip defines a sequence of UV rectangles and timing.

Scripting API

Animation.play(entity, "walk")
Animation.stop(entity)
Animation.set_speed(entity, 0.5)  -- half speed

if Animation.is_playing(entity) then
    log("Still animating")
end

Events on frames

A frame of a clip can carry triggers, and they fire in every runtime: a PlaySound plays its clip, and an EmitEvent reaches the entity’s script as on_animation_event(entity, { name, data }) - and, through the event bus, any script listening for it. Use them for frame data, such as a hitbox live on exactly the frames the clip says, rather than a timer kept beside the animation.

State machines

A clip set can be driven by parameters instead of direct calls:

Animation.start_state_machine(entity, "idle")
Animation.set_float(entity, "speed", vx)
Animation.set_bool(entity, "grounded", on_ground)
Animation.set_trigger(entity, "attack")
log(Animation.get_state(entity))

Property Tweens

Smoothly interpolate transform and color properties with easing functions.

Available Easing Functions

Linear, EaseInQuad, EaseOutQuad, EaseInOutQuad, EaseInCubic, EaseOutCubic, EaseInOutCubic, EaseInSine, EaseOutSine, EaseInOutSine

Scripting API

-- Tween position over 1.5 seconds
Tween.position(entity, 100, 200, 1.5, "EaseOutQuad")

-- Tween rotation
Tween.rotation(entity, 3.14, 2.0, "EaseInOutSine")

-- Tween scale
Tween.scale(entity, 2.0, 2.0, 0.5, "EaseOutCubic")

-- Tween sprite color (fade to red)
Tween.color(entity, 1, 0, 0, 1, 1.0, "EaseInQuad")

-- Cancel tweens
local id = Tween.position(entity, 0, 0, 2.0, "Linear")
Tween.cancel(id)
Tween.cancel_all(entity)

Tween.color fades world text as well as sprites.

Skeletons

A skeletal rig is bones as entities in a hierarchy, a skeletal_player playing clips on them and an optional skinned_mesh drawn over them (sorted with sprites by z_order). Animation.play, stop and set_speed reach a skeletal player as they do a sprite animator, and it can do more:

Animation.crossfade(entity, "run", 0.25)    -- fade the old pose out while it keeps playing
Animation.set_blend(entity, "run", 0.6)     -- mix a second clip in at the same phase

• Two-bone IK (ik_two_bone) bends a joint toward a target, and with ground plants an animated foot on the collider under it.
• Jiggle bones (jiggle) swing a chain after its pose - hair, tails, tentacles - with a max_angle per link that keeps a soft chain from folding.
• Cloth and rope (cloth, rope) are point grids the engine moves each frame and writes into the entity’s mesh; pins follow world transforms, so a flag on a swinging pole flies.

A v2 scene holds a rig ("parent" beside an entity’s "name"). See the Scripting API for every animation function.