[Bug] Props (vehicle-deck cars, cave cathedral columns) have no collision

[N1k4G]

The vehicle deck's cars and lorries and the cave cathedral's two speleothem columns are drawn but have no collision. The diver swims straight through all of them.

Blocked on a decision — see #119. How this gets fixed depends on which side of the WP-07 gameplay/presentation boundary props are classified on. Details at the bottom.

Reproduction

Driving the physics loop directly via window.gameAPI on main.

Cave cathedral columns

Both columns are features, neither appears in structures:

{kind:'caveColumn', x:88,  dTop:56, dBottom:98, wTop:9,  wBot:11, seed:5901},
{kind:'caveColumn', x:112, dTop:60, dBottom:95, wTop:6,  wBot:8,  seed:5902}

solidAt returns false across the entire footprint of column A — probed at every metre from x = 82 to x = 94 at d = 75, all open water. Swimming right from x = 80, the diver reaches x = 88.15 — dead centre of a column with an 11 m base — still reading solid: false.

This one is a documented choice rather than an oversight. src/sites.js:671-672:

// Neither introduces collision — solidAt() only tests the AABB
// structures list, and neither column is added there.

Wreck vehicle deck

12 cars and lorries at d: 39 (src/sites.js:455-466), none in structures. A probe grid over the car at x = 34 and the lorry at x = 54, sampled across d = 36.5 … 38.5, is entirely open water. Swimming right from x = 30, the diver passes through the car at x = 34 at t ≈ 8 s with no collision registered.

Probe placement matters here. Sampling at d = 39 reads solid, but that is the vehicle-deck floor slab ({x1:14, x2:78, dTop:39, dBottom:40, kind:'deck'}) — solidAt is inclusive on dTop. A probe at that depth cannot distinguish a car with collision from one without; it has to be taken at body height above the slab. (The .tmp/frontend-audit data records propProbeSolid: false at d = 39 — right conclusion, wrong probe point.)

Why this is blocked

WP-07 (#119) partitions site data into two documents:

gameplay.json     — [id, maxDepth, hasOverhead, entry, boatX, floor, ceiling, structures, badAir, …]
presentation.json — [id, name, surfaceMarker, features, visualZones, atmosphereProfiles, decorationRules]

solidAt() reads structures (gameplay). Cars and columns are features (presentation). tests/unit/site-assets.test.ts:127 asserts presentation can never carry structures, so after that merges the gap is enforced by a passing test.

That is the PR working as intended — its goal is that an art edit cannot reach collision. But it does mean the fix location moves: giving a car a hitbox stops being a one-line edit next to the car and becomes a deliberate gameplay-side entry, either promoting specific prop hitboxes into structures or adding a gameplay field that references prop ids.

Worth settling that classification on #119 before it merges, since changing it afterwards is a data migration rather than an edit.

Scope note

If props do gain collision, #101 and #122 (centre-point collision) are both adjacent: a car-sized AABB is small enough that a point-test diver would clip visibly into it, so extent probably wants sorting first or alongside.

[N1k4G]

Closing as a documented limitation, not a defect. Decision: props stay decoration.

The behaviour is real and reproducible — the diver swims through the vehicle-deck cars and both cave cathedral columns — but it is the intended consequence of WP-07's gameplay/presentation split (#119). Props are features, solidAt() reads structures, and tests/unit/site-assets.test.ts asserts the two documents stay disjoint.

Correcting something I said earlier in this issue

I wrote that changing this after #119 merges would be "a data migration rather than an edit". That was overstated. Reversing it later means adding an AABB to structures alongside the prop — an ordinary edit to sites.js plus a regenerate.

The real cost is different, and worth recording for whoever revisits this: position data would then live in two places. Move a car and forget its hitbox, and the collision box silently stays where the car used to be. If props ever do get collision, the thing to build is a way for a feature to declare its own hitbox that the generator lifts into gameplay, so the position stays authored once — not hand-paired AABBs.

If you want this later

Reopen and start there. The relevant anchors:

• src/sites.js:455-466 — the vehicle-deck cars and lorries
• src/sites.js:662-674 — the cave columns, with a comment already stating they carry no collision
• src/sites.js:797 — solidAt(), which reads only structures
• scripts/generate-site-resources.mjs — GAMEPLAY_FIELDS / PRESENTATION_FIELDS, where a hitbox field would need classifying

#122 is adjacent: a car-sized AABB is small enough that a point-test diver would clip visibly into it, so diver extent probably wants sorting first or alongside.