KCL files define the collision data for a course in Mario Kart DS. The header takes the following structure:
| Offset | Type | Meaning |
|---|---|---|
| 0x00 | VecFx32 * | Pointer to vertex list (fixed up at runtime) |
| 0x04 | VecFx16 * | Pointer to normal list (fixed up at runtime). These should be unit vectors. |
| 0x08 | void * | Pointer to triangle data (fixed up at runtime). This list is 1-indexed, so this really points 0x10 bytes before the data. |
| 0x0C | void * | Pointer to octree data (fixed up at runtime) |
| 0x10 | fx32 | Prism thickness |
| 0x14 | VecFx32 | Bounding minimum coordinate |
| 0x20 | u32[3] | Area width masks { x, y, z } |
| 0x2C | u32[3] | Area width shifts { x, y, z } |
| 0x38 | fx32 | Collision sphere radius |
The prism data in the file is stored in a way that makes collisions simpler to calculate. Prisms are derived from extruding a triangle by the prism thickness specified in the file header. Each triangle references one vertex from the vertex list. These triangles take the following structure:
| Offset | Type | Meaning |
|---|---|---|
| 0x00 | fx32 | Length |
| 0x04 | u16 | Vertex index. This is the index of one of the vertices of the face in the vertex list. |
| 0x06 | u16 | Surface normal index. Collision only works in one direction. |
| 0x08 | u16 | Vector 1 index |
| 0x0A | u16 | Vector 2 index |
| 0x0C | u16 | Vector 3 index |
| 0x0E | u16 | Collision attributes (see below) |
Next in the file is the octree data. In order to accelerate the collision calculation process, octrees allow for the lookup time to be significantly reduced by recursively partitioning the model into equal-sized boxes. When the collision sphere is within an octree's bounds, only collision prisms within that box need to be checked. Because the collision sphere has a nonzero radius, the octree bounds should be inflated by its radius to create a box with rounded edges.
Collision Attributes#
The collision attributes as specified in the collision prism data determine what should happen when each face is collided. Its structure is a 16-bit bit field like the following:| Bits | Meaning |
|---|---|
| 1 | Map2D shadow |
| 2-3 | Light ID (0-3) |
| 4 | Ignore drivers |
| 5-7 | Collision variant |
| 8-12 | Collision type |
| 13 | Ignore items |
| 14 | Is wall |
| 15 | Is floor |
The following are the collision types used in Mario Kart DS:
| Type | Meaning |
|---|---|
| 0 | Road |
| 1 | Slippery Road |
| 2 | Weak Offroad |
| 3 | Offroad |
| 4 | Sound Trigger |
| 5 | Heavy Offroad |
| 6 | Slippery Road 2 |
| 7 | Boost Panel |
| 8 | Wall |
| 9 | Invisible Wall (ignored by cameras) |
| 10 | Out of Bounds |
| 11 | Fall Boundary |
| 12 | Jump Pad |
| 13 | Road (no drivers) |
| 14 | Wall (no drivers) |
| 15 | Cannon Activator |
| 16 | Edge Wall (does not collide when on the ground) |
| 17 | Falls Water |
| 18 | Boost Pad w/ Min Speed |
| 19 | Loop Road |
| 20 | Special Road |
| 21 | Wall 3 |
| 22 | Force Recalculate Route |
