# Native entity collision filters and trace decisions

Static pass, 2026-10-11. Reproduce with `python3 scripts/analyze_native_collision.py`; check with `python3 scripts/test_native_collision.py`. [Generated evidence](native-collision.json) verifies original/disassembly hashes for both Linux ELF64 engines and retains five graphs per image plus CM_Trace windows. It evaluates **256 filter and 64 result-decision probes** against actual selected instruction addresses with supplied memory. No original process, collision callee or complete native function executes. These findings extend [native spatial services](NATIVE_SPATIAL.md).

## HIT-001: pass/related-object and contents filtering

SV_ClipMoveToEntities begins with an area query capped at **1024** indices. Its retained prologue derives a related-object word from the pass entity's field **0x200**, converting sentinel **1023** to **-1**; pass-entity sentinel 1023 also selects -1 without that entity lookup. Count <=0 or nonzero current result's first status word can end entity processing.

The bounded first candidate lane tests the following raw fields before model selection:

| Input | Native address/field |
| --- | --- |
| Pass entity index P | clip structure 0x74 |
| Candidate index C | current four-byte area-query element |
| Candidate related/owner-like word O | candidate object 0x200 |
| Previously derived pass-related word R | stack slot 0x2c |
| Content mask M | clip structure 0x78 |
| Candidate contents K | candidate object 0x1cc |

If **P !=1023**, candidate is rejected when **P==C**, **P==O**, or **R==O**. Pass sentinel 1023 bypasses those three comparisons. Independently, **M & K must be nonzero**. The contents test remains active with the sentinel.

Each engine has 128 first-lane probes: pass indices 1023/7/5/9, candidate index 7, related word 1023/5/9/-1, supplied pass-related -1/9 and contents 0/1/2/3 under mask 1. Contents 2 is nonzero but does not overlap mask 1; contents 3 does. First-match rejection and model-entry acceptance are reached through the original branches, not a gameplay execution harness.

Fields 0x200/0x1cc have owner-like/content-mask interpretations supported by comparisons and downstream collision calls. Full shared-object layout, legal entity domains, pass-related producers, linked-list/query capacity and the other unrolled filter lanes remain separate tasks.

## HIT-002: result status updates versus closer-hit replacement

The first post-CM_TransformedBoxTrace lane reads candidate result offset **0**. Nonzero sets current result status offset 0 to **1**, supplies candidate object word zero as the temporary hit identifier, and skips that lane's offset-4 test. If candidate offset 0 is zero, candidate offset **4** nonzero sets current status offset 4 to **1** and likewise supplies the temporary identifier.

Next the candidate float at result offset **8** is compared with current result offset 8. For finite values, only **candidate < current** reaches the copy/replacement gate. Equality or greater skips the copy. Thus status updates can precede—and survive—a rejected replacement. They are not the same decision as choosing a closer hit.

Thirty-two probes per image cover candidate statuses 0/1 at offsets 0/4, candidate float 0/0.25/0.5/1 and current float 0.5/1. Current statuses are initially zero in these fixtures. The restricted interpreter supports the selected MOVL/MOVSS/TESTL/CMPL/finite COMISS and branch forms only; unknown reads/opcodes, nonfinite comparisons and step bounds fail closed. Probe input floats are supplied collision results, not calculated intersections.

The retained copy path writes candidate object word zero into candidate result offset **52**, copies the **56-byte** result into the clip's current trace, and ORs the previous current offset-4 status into the copied offset-4 status. Other retained unrolled lanes have analogous calls/copies but are not evaluated by these first-lane probes. Initial nonzero current statuses, copy/OR composition, world/entity ties, NaNs, ordering and every lane need further validation.

The following raw result roles are corroborated across producer/consumer instructions:

| Result-relative offset | Observed role |
| ---: | --- |
| 0 | Status word that can stop further entity processing |
| 4 | Independently accumulated status; the crosshair branch compares it to exactly 1 |
| 8 | Float used to choose the closer result |
| 12/16/20 | Three endpoint words read by crosshair substitution |
| 52 | Hit identifier supplied from candidate object word zero |

CM_TraceThroughBrush writes status words at work offsets **0xcc/0xd0**, zero float at **0xd4**, and a brush-related word at **0xfc** in its containment paths. The status/float writes share the above relative spacing; work offset 0xfc is result-relative **48**, separate from the entity hit identifier at 52. The graphs/windows retain those writes; complete allsolid/startsolid/fraction/content member naming, plane layout and geometric proof remain open rather than inferred from spacing alone.

## HIT-003: collision model and transform routes

The retained clip graph selects models as follows:

- Candidate object word **0x1b0 nonzero** loads model index **0xa0** and calls **CM_InlineModel**.
- Otherwise it passes bounds pointers **object+0x1b4 / object+0x1c0** to **CM_TempBoxModel**. The byte test **object+0x1a9 &4** chooses the third argument **1** when set, **0** when clear. Capsule/flag identity and temporary-model ownership remain open.
- The subsequent **CM_TransformedBoxTrace** receives start/end, trace extents, selected model, contents mask and an additional mode word. Transform origin is **object+0x1e8**; orientation uses **object+0x1f4** when 0x1b0 is nonzero, otherwise the shared zero-initialized vector.

Three unrolled call sites and their related out-of-line branches are retained in each engine. CM_BoxTrace's wrapper calls CM_Trace with a shared vector and an extra zero argument; CM_TempBoxModel, CM_InlineModel and the brush-trace graph are also retained. This confirms the static model/transform routing without executing temporary-model mutation, brush planes, patches, capsule geometry or rotated-model results.

## Remaining work and Rust dependencies

RE-289–291 record first-lane filters, bounded result decisions and static model/result-field evidence. RE-288 remains open; RE-292 tracks every unrolled lane, existing-status and copy/OR composition, complete trace/entity fields, owner/count producers, model/flag/transform identities, collision internals/ordering and original-runtime/all-platform fixtures. A Rust collision contract must preserve exclusion relations, content overlap, status accumulation and strict hit replacement independently; a single nearest-hit operation would not capture the recovered status behavior.

The [MIX-001–003 follow-up](COLLISION_COMPOSITION.md) evaluates full copy/status composition in all three result lanes and world sentinel/zero-fraction decisions. Full candidate-loop/geometry/runtime behavior remains open under RE-292/296.