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fix(physics): #147 — far-town city/perimeter walls had no collision (portal-less buildings skipped)

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A town's outer/perimeter walls have NO collision even on a fresh login: the
player walks straight through them while houses block fine. Confirmed NOT a
frame issue — #146's bldOrigin probe showed Arwic buildings are correctly
framed (~12 m from the player, not km off), so the "#145 far-town frame"
premise was wrong here.

Root cause (dat-confirmed, Issue147ArwicBuildingsDumpTests): a perimeter wall
is stored in LandBlockInfo.Buildings as a doorless shell — 16 of Arwic's 30
buildings are PORTAL-LESS, ringing the town at 24 m intervals (x=12/132,
y=12/108). The building-collision cache loop skipped them via
`if (building.Portals.Count == 0) continue;` — a filter meant only for the
transit/entry feature (CellTransit.CheckBuildingTransit) that also dropped the
collision shell. Retail's find_building_collisions (0x006b5300) tests the shell
BSP independent of the portal list, so a doorless wall still collides.

Fix: don't skip portal-less buildings — cache them with an empty portal list
(no transit) but their collision shell (ModelId) intact. User-verified: Arwic
perimeter walls now block (Collided/Slid). Adds the dat-dump fixture test.

Suites green: Core 1569(+2 skip), App 468(+2 skip), UI 425, Net 317.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Erik 2026-06-24 16:24:48 +02:00
parent 31612e99c3
commit 9743537e62
2 changed files with 77 additions and 1 deletions
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14
src/AcDream.App/Rendering/GameWindow.cs
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@ -6957,7 +6957,19 @@ public sealed class GameWindow : IDisposable
uint lbPrefix = lb.LandblockId & 0xFFFF0000u;
foreach (var building in lbInfo.Buildings)
{
if (building.Portals.Count == 0) continue;
// #147 (2026-06-24): do NOT skip portal-less buildings. A town's
// PERIMETER WALL is a building with NO portals (you don't enter a
// wall segment through a door) — but it still needs its shell BSP
// registered for COLLISION. The original skip existed for the
// transit/entry feature (CellTransit.CheckBuildingTransit); dropping
// the whole building also dropped its collision shell, so a far
// town's city walls had ZERO collision and the player walked through
// them (Arwic: 16 of 30 buildings are portal-less wall segments
// ringing the town at 24 m intervals). Retail collides with a
// building's shell regardless of portals — find_building_collisions
// (0x006b5300) tests parts[0], independent of the portal list. So a
// portal-less building is now cached with an EMPTY portal list (no
// transit) but its collision shell (ModelId) intact.
var bldPortals = new System.Collections.Generic.List<AcDream.Core.Physics.BldPortalInfo>(
building.Portals.Count);