Models (.model)

A .model asset (8,780 in the install) is a DAT1 container with the type magic 0x6AE15C79. All 8,780 are LZ4-compressed with a zero wrapper tail. Observed Five have no geometry sections (portal, cine_traincrash_rearrooffire_spawner, tb_testbldg_globe_fountain, test_trash_can_breakable_stump, empty_weapon); the other 8,775 all have the vertex, index, mesh, look, UV and material sections below. Observed The geometry is +Y up. Observed

Numbers on this page are from a recorded census of the PC build 3373500; the install is no longer available. Observed

Sections

Tag	Name	Size	Content	Confidence
283D0383	Model Built	72 B	bounds and the vertex quantisation	Observed
A98BE69B	vertices	16 B each	packed position, normal and tangent	Observed
0859863D	indices	u16	plain 16-bit indices, no delta coding	Observed
78D9CBDE	meshes	64 B each	one record per submesh	Observed
06EB7EFC	look	16 B	four LODs, each (first mesh, mesh count)	Observed
16F3BA18	UV0	4 B per vertex	half-float u, v	Observed
3250BB80	materials	32 B each	material path and name offsets	Observed
5CBA9DE9	vertex colour		in 1,425 models	Observed
DCA379A2	skin data		in 3,470 models	Observed

Model Built (283D0383, 72 bytes)

Model Built72 bytesSunset44% known

Little-endian; floats are indexed from 0 in the census.

ProvenObservedSourcedInferredUnknownNot described

0

1

2

3

4

5

6

7

8

9

A

B

C

D

E

F

0x0

bounds centref32[3]

bounding sphere radiusf32

0x10

box half-extentsf32[3]

quantisation wordu32

0x20

unknownf32

LOD switch distancesf32[3]

0x30

unknownf32[3]

unknownf32

0x40

unknownf32

unknownu32

Offset	Size	Type	Field	Confidence	Notes
0x0	12	f32[3]	bounds centre	Observed
0xC	4	f32	bounding sphere radius	Observed
0x10	12	f32[3]	box half-extents	Observed	the box is centre ± half-extents
0x1C	4	u32	quantisation word	Observed	the low nibble N gives the position scale 2^−N; bits 4 to 15 take only the values 0, 16, 32, 48 and are unexplained
0x20	4	f32	unknown	Unknown
0x24	12	f32[3]	LOD switch distances	Inferred	15, 30, 110 in 6,335 models
0x30	12	f32[3]	unknown	Unknown
0x3C	4	f32	unknown	Unknown	2 in almost every model
0x40	4	f32	unknown	Unknown	8 in almost every model
0x44	4	u32	unknown	Unknown

The position scale is 2^−(word & 0xF) with no offset. Observed Evidence: the decoded minimum and maximum equal the stored box within two quanta in all 5,305 static models (and in 1,078 of 3,470 skinned ones; the other 2,392 skinned models exceed their box); 1x1_plane (nibble 12) decodes to ±0.5 and its y of 41 to 0.01001 equal to the built centre; seafloor_8x8 (nibble 12) to ±4.005 and seafloor_96x96 (nibble 9) to ±48.01 equal their half-extents (a fixed 1/4096 would give 6.0 for the latter). Observed Nibble distribution: 12 → 7,603 models, 8 → 516, 11 → 366, 10 → 193, 9 → 62, 7 → 22, 5 → 13, 6 → 5. Observed

Vertices (A98BE69B, 16 bytes)

Vertex16 bytesSunset75% known

ProvenObservedSourcedInferredUnknownNot described

0

1

2

3

4

5

6

7

8

9

A

B

C

D

E

F

0x0

positioni16[3]

wi16

packed normalu32

tangentu32

Offset	Size	Type	Field	Confidence	Notes
0x0	6	i16[3]	position	Observed	× 2^−N, no offset
0x6	2	i16	w	Observed	±32767 in most models; possibly a bitangent sign
0x8	4	u32	packed normal	Observed	the plane's word 0x200FFE00 decodes to (0, 1, 0) with the ALERT decoder
0xC	4	u32	tangent	Unknown	probably a packed tangent

The layout is the same as ALERT’s Sunset Overdrive branch. Sourced · ALERT Whether the normals are unit length over all vertices, and the vertex-colour format (probably a u32 per vertex), are not checked. Unknown

Meshes (78D9CBDE, 64 bytes)

Mesh entry64 bytesSunset53% known

ProvenObservedSourcedInferredUnknownNot described

0

1

2

3

4

5

6

7

8

9

A

B

C

D

E

F

0x0

bounding spheref32[4]

0x10

vertex startu32

index startu32

index countu32

vertex countu32

0x20

flagsu16

material indexu16

unknownu8[28]

0x30

… unknown

Offset	Size	Type	Field	Confidence	Notes
0x0	16	f32[4]	bounding sphere	Observed	centre xyz and radius
0x10	4	u32	vertex start	Observed
0x14	4	u32	index start	Observed
0x18	4	u32	index count	Observed	a multiple of 3
0x1C	4	u32	vertex count	Observed	upper 16 bits always 0
0x20	2	u16	flags	Observed	bit 0x10: indices are relative to the vertex start
0x22	2	u16	material index	Inferred	0 to 49; from ALERT's layout
0x24	28	u8[28]	unknown	Unknown

Over 37,148 meshes: vertex start + vertex count never exceeds the vertex count, index start + index count never exceeds the index count. Observed Flag 0x10 means the indices are relative to the vertex start. All 17,152 meshes with the flag have indices below their vertex count; of the 13,418 meshes without it and with a vertex start above 0, all have absolute indices within [vertex start, vertex start + vertex count); no mesh fits neither. Observed ALERT’s OBJ writer tests (flags & 0x10) == 0 for “relative”, the opposite. Observed

In 3,365 models the per-mesh vertex counts do not sum to the vertex total (the sum equals it in 5,410 of 8,775); the cause (LODs or meshes sharing vertex ranges, overlap versus gaps) is not established. Unknown

Look (06EB7EFC) and LODs

Four (u16 first mesh, u16 mesh count) pairs, one per LOD. Over the 8,775 models with geometry the distinct ranges are contiguous and together cover every mesh exactly. A model with fewer LODs repeats the last range: 4,225 models have 1 distinct LOD, 698 have 2, 3,759 have 3 and 93 have 4. Observed

UV0 (16F3BA18)

Half-float u, v at 4 bytes per vertex. On the 1 × 1 plane it gives (0,0), (0,1), (1,1), (1,0) with u = x + 0.5 and v = z + 0.5. Some models use 8 bytes per vertex (the ALERT get_uv variant); the second pair is probably a second UV set. Their count is not established. Observed

Materials (3250BB80, 32 bytes)

Per entry a u32 string offset for the .material path, a u32 for the material name, then six u32 (zero in the fixtures). The layout is taken from ALERT and the sampled strings match. Sourced · ALERT

Handedness

The 1 × 1 plane is symmetric and cannot show a mirror. Triangle (0, 1, 2) of the plane winds counter-clockwise about +Y in a right-handed frame, but whether the engine’s frame is left- or right-handed has not been decided. Unknown

What is the handedness of Sunset Overdrive’s world?

It needs an asymmetric reference: text geometry, a decal carrying text, or the minimap overlaid with zone placements (the hex placements are in world coordinates, Zones).

What do the unexplained bits of the quantisation word, the vertex w and the 8-byte UV variant mean?

Bits 4 to 15 of the word at +28 of Model Built take only 0, 16, 32, 48; vertex w is ±32767 in most models; some models carry a second UV pair. Skinned models (3,470) exceed their box, so skinning is needed to place them, which was not decoded.