Two ECS-native, deterministic namespaces for 2D motion, driven off the fixed
frame clock so replays and lockstep netcode reproduce every frame and every
eased value exactly. Both are pure computed-inline Q16.16 / integer math (no new
runtime, no heap) — the game stores a timer on a component and calls these each
frame, exactly the way Collision.* / Grid.* are used.
Anim.* — spritesheet frame animation:
- Anim.frame(timer,fps,count) -> int looping frame index
- Anim.once(timer,fps,count) -> int one-shot, clamps on the last frame
- Anim.pingpong(timer,fps,count) -> int bounce 0..count-1..0
- Anim.finished(timer,fps,count) -> bool has a one-shot run past its end?
- Anim.duration(fps,count) -> fixed seconds for one cycle
- Anim.cell_x/cell_y(frame,cols,cell) -> int source rect on a grid sheet
Tween.* — value interpolation over a timeline:
- Tween.progress/loop/yoyo(timer,duration) -> fixed normalized amount
- Tween.done(timer,duration) -> bool
- Tween.ease(t, mode) -> fixed shape by a literal curve 0..6,
the same curves as Ease.* (now
factored into a shared ease_eval)
- Tween.number/round/point/tint(from,to,t) blend a fixed / int / Vector / color
The typed blends reuse the existing fixed / Vector / color helpers, and
Tween.ease shares Ease.*'s exact formulas via the new ease_eval(mode,t) — one
source of truth for every easing curve in the engine.
examples/library/anim.ludic asserts 34 cases (frame math, clamping, ping-pong,
cell geometry, timeline clamp/loop/yoyo, rounding, color/vector blends, and
Ease.in == Tween.ease(.,1)); wired into x test (now 62 passed). Docs: Anim +
Tween sections with 16 per-symbol pages, inventory/coverage green. Seed
reseeded; the C-free bootstrap fixpoint holds.
The stateful sugar the proposal sketches (named clips, Anim.play, fluent
Tween.chain/parallel handles, and an auto-injected advance system) is deliberately
left as a follow-up — this lands the deterministic math core both halves stand on.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
32 lines
1,000 B
Markdown
32 lines
1,000 B
Markdown
---
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id: tween-round
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name: Tween.round
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category: tween
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kind: namespace-method
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tokens: Tween.round
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sig: Tween.round(from, to, t) -> int
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tip: Linear blend of two ints by amount t, rounded to the nearest int.
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order: 7
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ns: Tween
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member: round
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---
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Interpolates two <code>int</code> endpoints by amount <code>t</code> and rounds to the nearest integer (half up): <code>from + round((to - from) * t)</code>. The go-to for tweening a pixel position, a channel byte, or any integer field. Combine with <a href="tween-ease"><code>Tween.ease</code></a> for shaped motion.
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Parameters:
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- `from` — the value at `t = 0` (an `int`)
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- `to` — the value at `t = 1` (an `int`)
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- `t` — the blend amount (a `fixed`, usually 0..1)
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```ludic
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program Demo {
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property Slide { timer: fixed = 0.0 }
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model Card { Slide }
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handler Run phase Update {
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Slide.timer = Slide.timer + Time.delta()
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let t = Tween.progress(Slide.timer, fixed(1))
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let x = Tween.round(0, 320, Tween.ease(t, 2))
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print(x)
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}
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}
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```
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