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>
