OpenKh

This is a project centralizes all the technical knowledge of Kingdom Hearts series in one place, providing documentation, tools, code libraries and the foundation for modding the commercial games.

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Kingdom Hearts: Birth By Sleep - BCD

Found inside map .arcs the details of much of the file format remain unkown, however it does contain the collision data for the map.

Offset Type Description
0x0 uint32 Magic value. Always "@BCD"
0x4 uint32 Version number.
0x8 uint32 Collision Data Count
0xC uint32 Pointer to Collision Data
0x10 uint32[9] A whole bunch of unknowns
0x34 uint16 Vertex count
0x36 uint16 Face count
0x38 uint32 Vertex list offset
0x3C uint32 Face list offset
0x40 uint32 offset to unknown data
0x44 uint32 offset to unknown data
0x48 uint32 offset to unknown data
0x4C uint32 offset to unknown data

Vertex List

fvec4 vertices[header.vertex_count] found at vertex list offset.

Face List

List of header.face_count of the following structure, found at face list offset.

Offset Type Description
0x0 uint32 Unknown.
0x4 uint32 Unknown.
0x8 uint32 Unknown.
0xC uint32 Unknown.
0x10 short Vertex index 1
0x12 short Vertex index 2
0x14 short Vertex index 3
0x16 short Vertex index 4 *
0x18 short Unknown
0x1A short Unknown
0x1C short Unknown
0x1E short Unknown
0x20 uint32 Unknown
0x20 uint32 Unknown, possibly flags
0x20 uint32 Unknown
0x20 uint32 Unknown

Unknown data

The last 4 values in the header point to regions in the file after the Face List. Nothing is yet known about this data, except that it’s size seems to be proportional to the complexity of the associated map. The current working theory is that it is some kind of tree structure for optimizing collision queries.

Somewhere in the unknown data in the face structure should be flags that indicate if a face is a wall or floor, or if it’s a trigger, as the level exit triggers seem to be present in the collision data. How the game decides what to do when you walk into them is currently unknown.