The built-in eases cover the usual shapes, but a game often wants its
own: a coin that bounces twice, a door that overshoots and settles.
A new asset type holds such a curve, and keys and the Lerp node can
pick it instead of a built-in ease.
- New asset type "curve": points like in Vector art, x is t and y is
the value. A new curve is the straight line from (0, 0) to (1, 1).
- One pure evaluation in src/core/model/curve.ts serves the timeline
preview, the running game and the Lerp node.
- The curve always has one value per t. The end points stay at t 0
and 1, points cannot pass each other, and a handle that reaches past
its neighbour is shortened along its direction. Loading a hand-edited
file applies the same rules.
- Curve tab: click on the line to insert a point that keeps the shape,
click on free space to put one there, drag points and handles,
double-click or Delete removes, Alt-click toggles round and sharp.
Every step is one undo step.
- Presets: all 30 built-in eases plus Linear, fitted with adaptive
subdivision. Each stays within 0.4 % of the built-in ease.
- Preview: a dot runs along the curve once a second, a second dot
shows only the value. The Preview button stops it.
- Animation keys get "Curve" under Easing with a curve picker. Lerp
gets "Curve" under Ease, and its result may overshoot b.
- A missing or unpicked curve runs linear. The inspector says so, the
node shows it as a problem, and deleting a used curve warns with the
number of keys and Lerp nodes.
Tests:
- ./check.sh: 180 files, 2612 tests, CHECK EXIT 0
- GM_STEPS=1-6,25,53: ALL PASSED, 309 checks
- New e2e module 53 with 13 checks, all with the real mouse. Expected
values come from its own Bezier evaluation.
- Counter-checks bite: without Bezier evaluation 4 unit tests fail,
without handle clamping 2. In the browser, a key that cannot find its
curve, a click that sets no point and a handle drag that moves the
point all turn checks red.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
A key could only ease quadratically, which makes quick moves like a
sword swing feel soft. Animators know the Penner curves from CSS,
GSAP and Unity, so a key now offers all of them.
- Ten curves (Sine, Quad, Cubic, Quart, Quint, Expo, Circ, Back,
Elastic, Bounce), each in, out and in-out, next to Linear and Step.
- The inspector shows two fields instead of one long list: Easing,
and Direction only when a curve is picked. Switching the curve
keeps the direction. Coming from Linear or Step starts at in-out.
- Old projects keep working. ease-in/out/in-out now read as Quad and
are still saved under that name. New curves save as cubic-out,
back-in-out and so on.
- Back and Elastic overshoot on purpose. A number property with min
or max is clamped in play and preview, so a Back in from scale 0
does not flip the sprite. trackWriteAt now takes the property
definition, and animatedKind* is renamed to animatedDef*.
- The timeline marker still shows only the direction.
- In-out is built for every curve from its in-curve and its mirror.
easings.net uses own constants for Back and Elastic in-out, so our
Back in-out winds up about 5 % instead of 10 %.
Tests:
- ./check.sh: 165 files, 2413 tests, CHECK EXIT 0.
- 12 new unit tests in tests/core/easing-curves.test.ts: round trip
of all 30 values, start/end/midpoint of every curve, reference
values, only Back and Elastic leave 0..1, clamping in play and
preview, unknown values are rejected.
- e2e 25: ALL PASSED, 28 checks. New 25b-ii (3 checks) clicks both
fields and undoes the four choices. Check sum 1393 -> 1396.
- Counter-checks, each fails its test: no clamping (2), Quad saved
as quad-* (2), mirrored in-out wrong (2), curve lookup with `in`
instead of Object.hasOwn (1), no Direction field (e2e 25).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
adminandClaude Opus 5.5