Seasons

The world is one set of data with four seasons. Every layer below is selected from the data for one season, and the index order everywhere is 0 spring, 1 summer, 2 autumn, 3 winter. Observed Where the data is certain but the engine code that picks it was not read, the row says so. All counts are from a recorded census of the Tokyo track Brio, no longer re-checkable. Observed

Layer	Selected by	Confidence
Placement files	the .pgeo season-exclusion mask (Placement files); the two nibbles of the byte are equal in all 96,234 headers	mask Observed; nibbles Proven
Model per placed template	the season’s template library (Template libraries)	records Observed; season folder Inferred
Material instance per mesh	the mesh’s material group element for the season; −1 means the group’s summer element	Observed
Parent materials	bin.zip materials\<season>\<same hash>	contents Observed; season folder Inferred
Textures	the parameter’s path hash up the season’s parent chain, never the _x<season>x_ in a file name	Observed
Terrain far-field colour	the season’s terr_mega instances → TerrainColourTexture and TerrainNormalTexture	Observed
Ocean optics	the tz_oceanparams.tz zone whose exclusion mask admits the season → an OceanSettings.xml preset	data Observed; evaluation Inferred
uber_water colour	its parent materials, as for any material	Observed
Near-field ground splat map	the .mtxmoddxt file name suffix only	Unknown
Hand-placed instances and terrain clusters	the instance’s gameplay record season-exclusion mask; the two nibbles are equal in all 1,079 gameplay records of brio_00.pvs	mask Observed; nibbles Proven

Mesh material ids

Each mesh material group holds four i16 material ids (spring, summer, autumn, winter). Over all 113,868 modelbins of GeoChunk0 (407,461 meshes, all version 1.9 or later, 431,991 groups): Observed

Ids present (P spring, S summer, A autumn, W winter)	Groups
P S A W	210,401
− S − −	149,073
− S − W	71,808
P S A −	320
− S A W	261
P S − W	122
P S − −	6

The summer id is never −1, and a seasonal id is never equal to the summer id (0 of 704,423 seasonal ids). Therefore −1 is the only way a season shares summer’s material: id(s) = ids[s] != −1 ? ids[s] : ids[summer]. −1 cannot mean “not drawn”: 149,073 groups, including 2,319 of the 2,512 models/buildings/city models, have no seasonal id and would vanish outside summer. Every variant group has its own four ids, and the rule applies per group. Observed Each of the 704,423 seasonal ids points at an instance named <summer instance name>x<season>x with the season of its index and the same parent path. Observed

Seasonal ids exist in terrain (41,812 of 62,295 tbheightfield models, each with xspringx, xautumnx, xwinterx copies of GenMaterial, terr_mega and SomeDeformationMaterial1), HLOD and rock proxies, props, signs, barriers, rocks, trees, bushes, Houdini infrastructure, and 193 of 2,512 city buildings. Observed

Parent materials

In each of the three bin.zip archives the season folders hold exactly the entry names of the base folder, and the asset manifest lists only the base folder. Proven

The bin.zip manifest lists 419 materials as materials\_0xN.materialbin; the spring\, autumn\ and winter\ folders hold the same 419 hashed names. 358 are byte-identical in all four sets; 61 differ (31 in winter only, 22 in spring, autumn and winter, 5 in spring and autumn, 3 in spring and winter). The differences are data: switches and constants (for environment\plot.material the snow and wetness switches 0xE20DFFAC and 0xD0813282), and textures (kit_cty_urb_01_a_xsummerx_bclr becomes ..._xwinterx_bclr; foliage_worldtint_x<season>x_bclr; all water\* materials). Observed

A seasonal instance carries the same parent path as its summer instance, so a parent’s season can only come from the folder: season s reads materials\<s>\<hash>, and summer reads the flat file (the flat set is summer: for the 22 materials that differ in spring, autumn and winter it differs from all three folders). Observed The executable holds the lowercase season names and the string game:\media\tracks\%s\bin.zip, but the code forming the path was not traced. Inferred Shader defaults (DFPR, the end of every chain) have no seasonal copy; uber_branch bark materials keep FuzzBaseColor = moss_xsummerx_diff in winter. Observed

Textures follow the chain

No texture is chosen by name. The _x<season>x_ in swatch names is the authoring convention and holds no rule: winter data references summer-named swatches where the data says so (in a rural validation box, 8 of 224 textures). Observed In a Tokyo core box, 14 of 2,518 summer swatches and 183 of 2,492 winter swatches carry the other season’s tag, and each one sampled is the instance’s own parameter. Observed

Terrain far-field

In each 512 m cell the terrain meshes select the season’s GenMaterial, terr_mega and SomeDeformationMaterial1 instances by their material ids. Each defines TerrainColourTexture (the mainmap_... swatch) and TerrainNormalTexture (the submap_... swatch) by path hash, plus BlendMapScale and BlendMapOffset, which give the cell: X0 = 0.25 − offset.x / scale.x, Z0 = −offset.y / scale.y − 512.25 (offset (2.99756, 5.99463), scale (1/512.5, −1/512.5) gives X0 = −1536, Z0 = 2560). All 52 instances per season agree per cell in the rural box checked. Observed

Placements by season

Winter drops every summer-only grass file and adds snow overlays (*_snow building roofs, ornate walls, log piles, 0x77 files); the winter tree and bush libraries swap deciduous trees for bare …_wnt_… models (tre_lmt_elm_*, tre_lmt_maple_*, tre_cst_ash_*, tre_gbl_deciduous_*, tre_urb_ginkgo_*, bsh_gbl_elm_*, bsh_alp_pinus_mugo_*) and planters for their empty _a variant; spring swaps tre_gbl_cherry_* for blossom …_spg_… models. Observed A template name must be looked up in the placement’s own category library, because the winter planter names exist in both props.plib (unchanged) and trees.plib (the empty variant). Observed

Hand-placed instances and terrain clusters carry the same exclusion mask in their gameplay record. Over the non-heightfield, non-catalogue instances: 0x77 (winter only) 2,469, of which 2,466 draw a *_snow model; 0x88 (not winter) 178; 0xEE (spring only) 36; 0xDD (summer only) 31; 0x99 17; 0x33 3; 0xCC 1; 0xFF (never) 2; 0x00 (no limit) 26,374; no record 97,719 (17,382 of those are _snow models drawn all year, mostly alpine rocks). 2,004 _snow instances sit exactly on an instance of the same model without _snow. Observed Drawn over the whole map: summer 110,530, spring 110,513, autumn 110,520, winter 112,808; winter keeps the 2,468 instances with 0x77 that every other season drops and drops 207. Terrain clusters drawn: summer 17,868, spring 17,850. Observed

Not covered

• The near-field splat .mtxmoddxt is per season by file name only, and no data reference to them exists (no mtxmoddxt string in the executable, none in the .pvs). Unknown
• Run-time season effects outside the asset data (snow accumulation, wetness, weather presets, the FallbackGI\brio_<season> textures, crowds_<season>) are not described. Unknown