BCO (File Format)
A BCO contains the track's collision data in Mario Kart: Double Dash!!. It is split into 4 parts, where only 2 are known, and are listed below.
File Header
| Offset | Type | Description |
|---|---|---|
| 0x00 | String | File magic. Always will be 0003 in ASCII. |
| 0x04 | UInt16 | Grid width. |
| 0x06 | UInt16 | Length of grid. |
| 0x08 | Int32 | X Start of grid. |
| 0x0C | Int32 | Z Start of grid. |
| 0x10 | Int32 | Grid cell X size. |
| 0x14 | Int32 | Grid cell Z size. |
| 0x18 | Int16 | The number of entries in the last section. |
| 0x1A | Int16 | Possible padding. Always 0x0000. |
| 0x1C | UInt32 | Triangle indices offset. |
| 0x20 | UInt32 | Triangle list offset. |
| 0x24 | UInt32 | Vertex list offset. |
| 0x28 | UInt32 | Unknown section offset. |
| 0x2C | End of file header | |
Triangles
Triangles are parts of the collision format that are formed from 3 vertices. Triangles also have the collision type for the defined triangle. The structure is a 0x24 byte structure defined below.
| Offset | Type | Description |
|---|---|---|
| 0x00 | Int32 | The index of the first point of the triangle, from the vertex list. |
| 0x04 | Int32 | The index of the second point of the triangle, from the vertex list. |
| 0x08 | Int32 | The index of the third point of the triangle, from the vertex list. |
| 0x0C | Float | Unknown. |
| 0x10 | Int16 | X Direction of normal vector. |
| 0x12 | Int16 | Y Direction of normal vector. |
| 0x14 | Int16 | Z Direction of normal vector. |
| 0x16 | UInt16 | Collision Flags |
| 0x18 | Byte | Table for getting Min/Max X/Z values. |
| 0x19 | Byte | Unknown. |
| 0x1A | Int16 | Neighboring Triangle 1 |
| 0x1C | Int16 | Neighboring Triangle 2 |
| 0x1E | Int16 | Neighboring Triangle 3 |
| 0x20 | UInt32 | Padding. |
| 0x24 | End of section. | |
Vertices
Vertices are sets of 3 floats that form a triangle. Each vertex structure is defined in a 0x0C byte structure below.
| Offset | Type | Description |
|---|---|---|
| 0x00 | Float | X position of the vertex. |
| 0x04 | Float | Y position of the vertex. |
| 0x08 | Float | Z position of the vertex. |
| 0x0C | End of section. | |
Unknown Section
This is a section with an unknown purpose. The number of entries is defined in byte 0x18 in the header. The 0xC byte structure is defined below.
| Offset | Type | Description |
|---|---|---|
| 0x00 | UInt16 | Collision flag |
| 0x02 | Int16 | Sound ID |
| 0x04 | UInt32 | Unknown. |
| 0x08 | UInt32 | Unknown. |
| 0x0C | End of section. | |
Collision Flags
Each triangle face has as collision flag that defines how the face acts when the player interacts with it. This can define whether it's sand, mud, ice, and more. Each flag is two bytes, but only the first one determines its basic property
| ID | Description |
|---|---|
| 0x00 | Sand / Offroad mud |
| 0x01 | Road |
| 0x02 | Item and Player Wall |
| 0x03 | Medium Offroad (typically grass) |
| 0x04 | Slippery Ice |
| 0x05 | Out of bounds |
| 0x07 | Speed Boost |
| 0x08 | Speed Boost |
| 0x09 | Cannon Boost |
| 0x0A | Out of bounds |
| 0x0C | Sand (Weak Offroad) |
| 0x0D | Pipe teleportation |
| 0x0E | Out of bounds |
| 0x0F | Out of bounds |
| 0x10 | Quicksand Sinkhole |
| 0x11 | Road (Peach Beach sand) |
| 0x12 | Player-Only Wall |
| 0x13 | Sand out of bounds |
| 0x37 | Speed Boost |
| 0x47 | Speed Boost |
The second byte gives additional properties to a flag, like particle / sound effects on the driveable flags or a connected respawn point in the BOL for the out of bounds flags.
Tools
The following tools can handle BCO files:
- Collision Tools, by Blank
- Wexos's Toolbox, by Wexos (only export)