Terrain clusters

The ground is not a height map at run time: each 512 m cell ships its surface as cluster models under scene/tbheightfield/, already in world metres, carrying the ground, roads, pavements, decals and water surfaces. The ground mesh has POSITION and NORMAL only, with no UVs; colour comes from per-cell textures (Far-field colour and Near-field ground). Observed

Counts come from a recorded census of the Tokyo track Brio (23,941 heightfield instances); the install is no longer available. Observed

Cluster families

File family	Holds	Confidence
autoterrain_<cell>_clusterNNN.i.modelbin	the real surface (ground, roads, pavements, decals, water), split into clusters; each cluster’s LODs are separate files with consecutive numbers; some clusters exist once per season	Observed
autoterrain_<cell>_cb_clusterNNN	an underlay drawn 0.5 m below the surface (instance y = −0.5): a coarse ground mesh, a second copy of the roads and the water, and an OCC_Terrain occluder cluster	Observed
autoterrain_<cell>_ul_clusterNNN	the whole cell as one LOD1 mesh (the distance proxy of the bare clusters)	Observed

The cell labels in file names are cell index × 1023; autoterrain_x-1023_z-10230 is cell (−1, −10) and a cell covers [512 i, 512 (i+1)) m. Observed

Which clusters are drawn

Which clusters draw comes from the hand-placed instance file, not from file names. Every heightfield cluster is drawn by exactly one instance: 16,489 of 16,489 bare LOD0 files and 3,153 of 3,153 _cb files are the band-0 model of exactly one instance; LOD1 to LOD3 files and _ul files are never a band-0 model. The instance carries the cluster’s LOD rows, LOD profile group and gameplay record. Every shipped LOD row of the 23,941 heightfield instances is a heightfield cluster. Observed

• _cb instances (3,153) use LOD profile group 19, the only group with no main-view (pass 2) record (passes 0, 1, 8, 9 only; 298 more group-19 instances have no shipped model): not drawn in the near view. They are also the only heightfield instances whose transform is not the identity (y −0.5). What passes 0, 1, 8 and 9 are (shadow cascades, reflections?) is not traced. Observed
• _ul instances (2,278) and 8 bare ones draw nothing in band 0 (band row 0x7F): distance proxies (HLOD parents of the bare clusters). Observed
• Bare instances have the identity transform at the origin, band 0 is the LOD0 cluster. 2,013 of them, all at the map border (LOD groups 17 and 18, band 0 = [0, 110 or 265 m)), had their LOD0 stripped from the build; the first later band whose model shipped is the one to use. Observed

Seasonal clusters

2,262 bare instances carry a gameplay record with a season-exclusion mask: 0xDD (summer only) 606, 0xEE (spring only) 588, 0x88 (not winter) 1,022, 0x77 (winter only) 46. Seasonal clusters come in pairs that cover the same ground; for example the rice paddies of autoterrain_x-3069_z5115 have clusters 070 (0xDD) and 074 (0xEE), 018 and 014, 042 and 038 (PLN_Lake_RicePaddy water, its _DistanceFade mesh and the paddy ground). Drawing every LOD0 file would draw both copies: the paddy box x −1500..−1100, z 2600..3000 would have 90,275 water texels covered twice in the summer far-field bake of cell (−3, 5); selected by the instance records it has 0 in summer (224,179 water texels) and 0 in spring (75,897, using clusters 014, 038, 074 instead of 018, 042, 070, and 004 and 099 summer-only). Observed Six bare instances carry a route or tag. Observed

Material families on the ground

Family	Used for
terr_mega	ground (GenMaterial*, terr_mega*, SomeDeformationMaterial*)
uber_megaroad, uber_megaroad_edge	rural roads
uber_road	city roads
uber_roaddecal, uber_roaddecalretro	paint, crossings, kerb grills, seams: coplanar layers drawn over the road
environment_plot	pavements
uber_water, ocean, ocean_shoreline	rivers, lakes, ponds, rice paddies, sea (Water)

All rows Observed. Families are recognised from the .shaderbin at the end of each material’s parent chain, not from names. Observed The terrain meshes also contain exactly repeated triangles and a few zero-area ones; a repeat with the opposite winding is how thin parts are made two-sided. Observed

Decal layers on the surface

Road decal meshes lie 5 to 25 mm above the surface under them: measured on 1,042 road-decal meshes, patch stacks step about 1 mm per layer (7.8, 8.8, 9.9, 10.7 mm) and paint lines sit about 17.6 mm up; 209 facade decal meshes sit a median 2.2 mm in front of the wall. The vertex positions are quantised to 0.98 mm, so these offsets are deliberate. Observed See Decals.