# Regional stream overlap and L4RA route-corridor review · r428

## Region files are overlapping alternatives

The eight cleaned city GLBs were compared pairwise at every repeated mesh name and full instance transform. The payload identity check includes POSITION, NORMAL, TEXCOORD_0, COLOR_0, indices, primitive mode, material metadata, embedded base-color image bytes, and sampler values. The reproducible report is [`city-region-pairwise-overlap-r428.json`](city-region-pairwise-overlap-r428.json), generated by [`audit_nfsu2_all_region_overlaps.py`](../tools/audit_nfsu2_all_region_overlaps.py).

The main overlap is L4RA/L4RD: 92,187 shared placement signatures, 92,111 exact payload matches, and 76 same-name/same-transform signatures with different payloads. L4RB/L4RG share 1,215 exact signatures. The other conflicting pairs are L4RA/L4RC (2), L4RC/L4RD (2), and L4RH/L4RR (5). Across the 28 region pairs these are 85 conflicting pair records; some could refer to one signature repeated across more than one pair.

This supports the existing executable trace: the game selects one `STREAML4R*.BUN` for a world entry. The region files are co-located stream/event alternatives, not adjacent tiles. The eight-region union remains an experiment and must not be treated as the original continuous world.

## L4RA route-corridor scan

Host Chrome loaded the regular single-region L4RA city, then ran the viewer's route-corridor scan against all 832 recovered L4RA routes. Samples were placed every 2 m along each supported route and checked at the center plus 1.2 m to either side against the extracted `XB_` building triangles at car height.

- 86,285 route-center samples had matching road support.
- The scan examined 258,833 car-width sample positions.
- 15 positions intersected two placed groups: `XB_HARBORA_NEON_1A_LL_00` (14 samples across routes 415, 567, and 570) and `XB_WATERTREATMENT_1A_CK_00` (one sample at route 1020, distance 0).

Route 415's ordinary chase view shows the car on the marked multilane road; the nearby road/object triangle-intersection check found no intersection at that view. The route 1020 start is at an industrial junction/apron, with several structure bases touching the road surface. The geometry check confirms a few triangle-level edge intersections there, but the screenshot does not show a broad building mass across the drivable lane. The sampled results identify localized boundaries; they do not prove every street or unsampled surface is correctly placed.

## Road-surface clipping experiment

At route 1020, `?clipRoadIntersectingTriangles` removed 1,117 building triangles in the 240-unit render radius. The same-camera comparison shows a large foreground object cut into a wedge, which is more visibly damaged than the baseline. This broad clipping pass was not enabled in the normal renderer. It needs better source-placement evidence or a tightly scoped method before it can improve the export.

- [Route 1020 baseline](../webgl-city/review/images/571-r428-l4ra-route1020-baseline.png)
- [Route 1020 clipping diagnostic](../webgl-city/review/images/572-r428-l4ra-road-clipping-diagnostic.png)
- [Route 415 road view](../webgl-city/review/images/573-r428-l4ra-route415-highway.png)
- [Scrollable screenshot review feed](../webgl-city/review/)