Verlet cloth on a bilinear patch between 4 anchors, N=10 grid,
structural/shear/bend constraints, 5 relaxation iterations at a fixed
1/60 substep. Wind is applied per FACE so hypar twist genuinely sheds
load rather than being cosmetic.
Two deviations from PLAN3D worth flagging:
- Load is read from each constraint's XPBD Lagrange multiplier, not from
FABRIC_K * leftover-stretch. After a fixed iteration count the leftover
stretch is solver error, not fabric strain, so the naive reading came
out ~50x hot (60 kN peaks on a 5x5 m sail). The multiplier is the real
constraint impulse, which the statics assert confirms by balancing the
corner reactions against the applied wind to 8%.
- Wind uses a signed square (d*|d|) rather than clamp(d)^2, so the
leeward face is pushed too. A sail is double-sided.
The sim core deliberately does not import three.js: it runs headless
under node today, stays allocation-free in the hot loop, and replays
bit-for-bit. createSailView() pulls three in lazily for rendering.
Loads land in real newtons (~1-4 kN on a 5x5 m sail in a 34 m/s storm),
so hardware ratings are real working load limits.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
selftest.html only imports; each lane owns js/tests/<letter>.test.js. Five lanes
sharing one selftest.html would be the single guaranteed merge conflict in the
repo, so the stubs are pre-created with each lane's PLAN3D asserts written into
the header.
No rAF anywhere: it's throttled in a hidden tab, so a rAF-driven selftest would
pass only while you watch it. fixedLoop() drives time instead.
Lane A's suite covers the §5-A acceptance criteria, including "camera never
clips through house" — stated as the underlying invariant (no solid between the
player's head and the camera) so it survives Lane E swapping the house GLB.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The yard's meshes are placeholders; its layout is not. Anchor positions, ground
heights, the garden rect and the sun direction are what the other lanes build
against, so Lane E's GLBs drop into named slots without anyone re-deriving them.
Sun sits in the north (Australian yard), which puts the house's yard-facing wall
in permanent backlight. That's correct, but the fascia line carries three of the
seven anchors, so sky fill is turned up to keep it readable rather than a void.
Camera collision resolves toward the geometry, not away from it: clamping up to
a comfort distance after the raycast is what put the camera 17cm inside the
north wall. Ground is handled by heightAt() instead of a raycast — exact, can't
be tunnelled, and free.
main.js runs a fixed-dt accumulator so sim modules only ever see FIXED_DT. That
is what lets selftest fast-forward a 90s storm and get the numbers the player
got. Nothing auto-runs on import; index.html calls boot().
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Types, tuning constants ported from the prototype, a seeded PRNG and Emitter,
plus checkContract() — the tripwire that catches a lane drifting from its
interface at merge time instead of three lanes later.
createStubWind() ports the prototype's gust shape (telegraph 1.5s, ramp 0.8s,
hold 1.7s, fade 1.0s) so B and D can develop before Lane C lands weather.js.
Its schedule is precomputed at construction, which keeps sample() pure in t —
the selftest samples out of order and must get the same answer.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
