secretsplash/doc/splashbundle.md

SPLASHPACK Binary File Format Specification

All numeric values are stored in little‐endian format. All offsets are counted from the beginning of the file.

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1. File Header (32 bytes)

Offset	Size	Type	Description
0x00	2	char	'SP' – File magic
0x02	2	uint16	Version number
0x04	2	uint16	Number of GameObjects
0x06	2	uint16	Number of Navmeshes
0x08	2	uint16	Number of Texture Atlases
0x0A	2	uint16	Number of CLUTs
0x0C	2	uint16	Player Start X
0x0E	2	uint16	Player Start Y
0x10	2	uint16	Player Start Z
0x12	2	uint16	Player Rotation X
0x14	2	uint16	Player Rotation Y
0x16	2	uint16	Player Rotation Z
0x18	2	uint16	Player Height
0x1A	2	uint16	Reserved (always 0)

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2. Metadata Section

2.1 GameObject Descriptors (56 bytes each)

Offset (per entry)	Size	Type	Description
0x00	4	uint32	Mesh Data Offset
0x04	4	int32	X position (Fixed-point)
0x08	4	int32	Y position (Fixed-point)
0x0C	4	int32	Z position (Fixed-point)
0x10	36	int32[9]	3×3 Rotation Matrix (Fixed-point)
0x34	2	uint16	Triangle count
0x36	2	int16	Padding

Mesh data for each GameObject is located at meshDataOffset.

2.2 Navmesh Descriptors (8 bytes each)

Offset (per entry)	Size	Type	Description
0x00	4	uint32	Navmesh Data Offset
0x04	2	int16	Triangle count
0x06	2	int16	Padding

Each triangle in a navmesh is defined by 3 int16 vertices (6 bytes per vertex).

2.3 Texture Atlas Descriptors (12 bytes each)

Offset (per entry)	Size	Type	Description
0x00	4	uint32	Pixel Data Offset
0x04	2	uint16	Atlas Width
0x06	2	uint16	Atlas Height
0x08	2	uint16	Atlas Position X (VRAM origin)
0x0A	2	uint16	Atlas Position Y (VRAM origin)

Pixel data is stored as uint16[width * height].

2.4 CLUT Descriptors (12 bytes each)

Offset (per entry)	Size	Type	Description
0x00	4	uint32	CLUT Data Offset
0x04	2	uint16	CLUT Packing X (in 16-pixel units)
0x06	2	uint16	CLUT Packing Y
0x08	2	uint16	Palette entry count
0x0A	2	uint16	Padding

CLUT pixel data is stored as uint16[length].

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3. Data Section

3.1 Mesh Data Block (per GameObject)

Each mesh is made of triangles:

Triangle Layout (52 bytes):

Field	Size	Description
Vertex v0	6	x, y, z (int16)
Vertex v1	6	x, y, z (int16)
Vertex v2	6	x, y, z (int16)
Normal	6	nx, ny, nz (int16)
Color v0	4	RGB + padding (uint8 × 4)
Color v1	4	RGB + padding (uint8 × 4)
Color v2	4	RGB + padding (uint8 × 4)
UV v0	2	u, v (uint8 × 2)
UV v1	2	u, v (uint8 × 2)
UV v2	2	u, v (uint8 × 2)
UV padding	2	uint16 (always 0)
TPage	2	Texture page info
CLUT X	2	Position in VRAM (X / 16)
CLUT Y	2	Position in VRAM Y
Final padding	2	uint16

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3.2 Navmesh Data Block

Each triangle is 3 vertices (int16 x/y/z), total 18 bytes per triangle.

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3.3 Texture Atlas Data Block

Pixel data stored as uint16[width * height].

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3.4 CLUT Data Block

Pixel data stored as uint16[length].

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