f7ff9f4eea
Port every current containment, overlap, walkable, and six-path moving-collision query to immutable integer-indexed assets behind a graph-authoritative referee. Exact synthetic, installed-DAT, complete-resolver, and zero-allocation gates prove bit-identical behavior before connected dual publication. Co-authored-by: OpenAI Codex <codex@openai.com>
87 lines
3.7 KiB
Markdown
87 lines
3.7 KiB
Markdown
# Slice I4 - differential flat BSP traversal
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**Date:** 2026-07-25
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**Scope:** Modern Runtime Slice I4 only
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**Behavioral boundary:** the new integer-indexed traversal is a shadow
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implementation. The parsed-DAT graph remains production-authoritative until
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the Slice I5 connected shadow gate and Slice I6 cutover.
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## Result
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`FlatBspQuery` now ports every collision entry point used by the current
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runtime over immutable, integer-indexed nodes and polygon ranges:
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- point-in-cell;
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- sphere/cell overlap;
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- static sphere/polygon overlap;
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- swept sphere/polygon time-of-impact;
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- walkable polygon selection;
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- solid and solid-polygon traversal;
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- the complete six-path moving-collision dispatcher.
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The port preserves retail's traversal order, strict comparisons, early
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returns, and mutable query state. The positive child remains first where
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retail visits it first; the negative child observes every valid-sphere,
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contact, path, slide, and candidate mutation made by the positive child.
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Only `BSPQuery.PolygonHitsSpherePrecise`, which is independent of graph
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storage, is shared with the existing graph oracle.
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`CollisionTraversal` is the narrow temporary referee seam. Production starts
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in `Graph` mode. Tests can run a cloned complete resolver in `Flat` mode, and
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a missing flat asset fails explicitly instead of falling back to the graph.
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Slice I6 removes this representation switch after connected acceptance.
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## Retail oracle
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The implementation follows the consolidated pseudocode and boundary table in
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[`2026-07-25-slice-i-collision-layout-oracle.md`](2026-07-25-slice-i-collision-layout-oracle.md),
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including:
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- `BSPTREE::find_collisions` at `0x0053A440`;
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- `BSPNODE::point_inside_cell_bsp` at `0x0053C1F0`;
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- `BSPNODE::sphere_intersects_cell_bsp` at `0x0053C260`;
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- `BSPNODE::sphere_intersects_poly` at `0x0053CA30`;
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- `BSPNODE::sphere_intersects_solid` at `0x0053CAF0`;
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- `BSPNODE::find_walkable` at `0x0053CC80`;
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- `BSPNODE::sphere_intersects_solid_poly` at `0x0053CD50`;
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- `BSPLEAF::find_walkable` at `0x0053D6F0`.
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The same oracle records the cross-checks against ACE master
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`65f092...` and Chorizite DatReaderWriter `c535987...`. Retail remains the
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authority where those references differ.
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## Differential evidence
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The referee compares scalar results and all stateful outputs by exact float
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bits. It covers selected polygons, vectors, planes, path state, collision and
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object flags, contact-plane writes, final `ResolveResult`, persistent body
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state, and full cell membership.
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| Gate | Executions | Result |
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|---|---:|---:|
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| Null, on-plane, radius-equality, equal-candidate, multi-polygon, and deep-tree fixtures | 4 focused fixtures | 0 mismatches |
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| Static and swept overlap randomized sweep | 10,000 paired cases | 0 mismatches |
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| Walkable randomized sweep | 5,000 paired cases | 0 mismatches |
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| Six dispatcher paths | 6 complete transition fixtures | 0 mismatches |
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| Installed-DAT sweep across `0x8A02016E`, `0x8A02017A`, and `0xA9B4013F` | 7,500 randomized cases | 0 mismatches |
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| Complete graph/flat resolver sequences | 1,200 frames | 0 mismatches |
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| Warmed flat traversal | 10,000 iterations | 0 managed bytes |
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The installed-DAT gate randomizes points, spheres, movement, insert paths,
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orientations, scale, and boundary values. No tolerance band is used.
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## Verification
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- focused differential tests: 13 passed;
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- complete Core suite: 3,276 passed / 2 skipped;
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- `git diff --check`: no whitespace errors;
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- full Release build: passed;
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- complete Release suite: 8,384 passed / 5 skipped.
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No divergence-register row changes are required. This slice changes the
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storage representation exercised by the referee, not production gameplay
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behavior. Slice I5 next publishes the prepared flat assets alongside the
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current graph under one landblock generation and runs the connected shadow
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gate.
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