Collision Index Data (File Format)

The collision index data structure defines collision geometry and materials. It can be found in the MREA format as well as the DCLN format.

Format

The structure is basically just a sequence of arrays. In Metroid Prime 2, the collision material field was extended from 32 bits to 64 bits, and a new array was added in between the triangle and vertex arrays. Other than that, the format is the same across all games.

Type	Count	Name	Notes	MP1	MP2+
u32	1	Collision Material Count	Count of collision materials in the mesh.	✔	✔
u32/u64	Collision Material Count	Collision Material Array	Array of bitfields that controls the collision material/properties. This is a 32-bit field in Metroid Prime, and a 64-bit field in every game after. See below for details.	✔	✔
u32	1	Vertex Index Count	Count of vertex material indices. Matches the number of vertices in the collision mesh.	✔	✔
u8	Vertex Index Count	Vertex Index Array	Array of vertex material indices. Each entry maps the corresponding vertex to a collision material from the Collision Material Array.	✔	✔
u32	1	Edge Index Count	Count of edge material indices. Matches the number of edges in the collision mesh.	✔	✔
u8	Edge Index Count	Edge Index Array	Array of edge material indices. Each entry maps the corresponding edge to a collision material from the Collision Material Array.	✔	✔
u32	1	Triangle Index Count	Count of triangle material indices. Matches the number of triangles in the collision mesh.	✔	✔
u8	Triangle Index Count	Triangle Index Array	Array of triangle material indices. Each entry maps the corresponding triangle to a collision material from the Collision Material Array.	✔	✔
u32	1	Edge Count	Count of edges in the collision mesh.	✔	✔
Edge	Edge Count	Edge Array	Array defining all edges in the collision mesh. Each edge is defined with two vertex indices.	✔	✔
u32	1	Triangle Count	Count of triangles in the next array. Note this is technically a count of the number of indices in the next array, not the number of triangles, so you need to divide it by 3 to calculate the actual triangle count.	✔	✔
Triangle	Triangle Count / 3	Triangle Array	Array defining all triangles in the collision mesh. Each triangle is defined with three edge indices. If the triangle's material has the Flipped Tri flag enabled, then reverse winding order; otherwise use the indices in order.	✔	✔
u32	1	Unknown Index Count	This array is only in Metroid Prime 2 and later.	✖	✔
u16	Unknown Index Count	Unknown Index Array	This array is only in Metroid Prime 2 and later.	✖	✔
u32	1	Vertex Count	Count of vertices in the next array.	✔	✔
Vector3f	Vertex Count	Vertex Array	Array defining all vertices in the collision mesh.	✔	✔

Edge

Offset	Type	Name
0x0	u16	Vertex Index A
0x2	u16	Vertex Index B
0x4	End of Edge

Triangle

Offset	Type	Name
0x0	u16	Edge Index A
0x2	u16	Edge Index B
0x4	u16	Edge Index C
0x6	End of Triangle

Collision Materials

Collision materials are basically properties mapped to every vertex, edge, and triangle in the collision mesh that controls how the game reacts when an object touches it. It controls things like, for example:

What sound effect plays when the player walks on the surface
Which actors are allowed to pass through the collision
Whether the player is allowed to stand on the surface or if it should be treated as a wall

... among some other things. This field is 32 bits in Metroid Prime, and was extended to 64 bits in Metroid Prime 2 and every game after. Prime 2 and 3 share the same property values, whereas Prime 1 and DKCR have unique property sets. In Prime 2 and on, the majority of the fields in the upper 32 bits are only meant for internal use and aren't used by MREA or DCLN collision assets. (These bits exist internally in Prime 1 as well, but they aren't exposed to the collision file format.)

The surface type properties controls what physical material the surface is made of, which changes the sound effect that plays when the player walks/jumps on the surface and in some cases, what particle effect plays on it. In the Metroid Prime series, rather than embedding an enum to set the surface type, each surface type is assigned its own bit. This technically allows for multiple surface types to be set on the same geometry. For sound effect playback, the bit with the largest value takes priority.

Metroid Prime

Bit	Hex	Name	Description
0	0x00000001	Unknown	This is a default flag set on most surface types. (Note: This isn't an unknown flag, it's just literally named "Unknown".)
1	0x00000002	Stone	Stone surface type.
2	0x00000004	Metal	Metal surface type.
3	0x00000008	Grass	Grass surface type.
4	0x00000010	Ice	Ice surface type.
5	0x00000020	Pillar	This flag is toggled on most pillar structures. Unknown function (possibly has something to do with how the morph ball camera interacts with the surface?).
6	0x00000040	Metal Grating	Metal grating surface type.
7	0x00000080	Phazon	Phazon surface type. If the active AreaAttributes object in this room has the Phazon Type enum set, this collision will cause the player to take Phazon-type damage.
8	0x00000100	Dirt	Dirt surface type.
9	0x00000200	Lava	Lava surface type. The sound effects for this surface type are in the LavaWorld AGSC, so it won't play back correctly outside of Magmoor.
10	0x00000400	Unknown	Unknown surface type found in a few rooms in Magmoor (some walls in Geothermal Core and Plasma Processing, the floors in Save Station A, and the ceiling in Save Station B). Footstep SFX sounds like stone.
11	0x00000800	Snow	Snow surface type.
12	0x00001000	Slow Mud	Slow mud surface type. The player's speed is reduced while walking on this surface. This is normally unused (only found in a few spots where you can't actually walk on it).
13	0x00002000	Halfpipe	Indicates this surface is a half-pipe, which changes how morph ball physics are calculated.
14	0x00004000	Mud	Mud surface type. Same as Slow Mud except it doesn't slow down the player. This is normally unused (only found in a few strange spots in Life Grove).
15	0x00008000	Glass	Glass surface type.
16	0x00010000	Shield	Shield surface type. Generally used on collision for force fields.
17	0x00020000	Sand	Sand surface type.
18	0x00040000	Shoot Thru	If this flag is enabled, projectiles can pass through this surface. This is used liberally in Prime 1 to make projectile collision appear more accurate.
19	0x00080000	Solid	If this flag is disabled, no actors can collide with this surface.
20	0x00100000	Unknown	Seems to be set on everything? Not a surface type and no noticeable effect from turning it on/off.
21	0x00200000	Camera Thru	If this flag is enabled, the morph ball camera can pass through this surface.
22	0x00400000	Wood	Wood surface type.
23	0x00800000	Organic	Organic surface type.
24	0x01000000	Unknown
25	0x02000000	Redundant Edge/Flipped Tri	Triangles with this flag enabled are flipped around.
26	0x04000000	See Thru	Indicates this surface is an invisible wall. Unknown function.
27	0x08000000	Scan Thru	If this flag is enabled, this surface doesn't block lock-ons in any visor.
28	0x10000000	AI Walk Thru	If this flag is enabled, AI actors can pass through this surface.
29	0x20000000	Ceiling	Indicates this surface is a ceiling.
30	0x40000000	Wall	Indicates this surface is a wall.
31	0x80000000	Floor	Indicates this surface is a floor.

Metroid Prime 2/3

Bit	Hex	Name	Description
0	0x00000000 00000001	Unknown	This is a default flag set on most surface types. (Note: This isn't an unknown flag, it's just literally named "Unknown".)
1	0x00000000 00000002	Stone	Stone surface type.
2	0x00000000 00000004	Metal	Metal surface type.
3	0x00000000 00000008	Grass	Grass surface type.
4	0x00000000 00000010	Ice	Ice surface type.
5	0x00000000 00000020	Pillar	This flag is toggled on most pillar structures. Unknown function (possibly has something to do with how the morph ball camera interacts with the surface?).
6	0x00000000 00000040	Metal Grating	Metal grating surface type.
7	0x00000000 00000080	Phazon	Phazon surface type. This collision will cause the player to take Phazon-type damage.
8	0x00000000 00000100	Dirt	Dirt surface type.
9	0x00000000 00000200	SP_Metal	Alternate metal surface type.
10	0x00000000 00000400	Glass	Glass surface type.
11	0x00000000 00000800	Snow	Snow surface type.
12	0x00000000 00001000	Fabric	Fabric surface type.
13	0x00000000 00002000	Halfpipe	Indicates this surface is a half-pipe, which changes how morph ball physics are calculated.
14	0x00000000 00004000	Unused3	Unused in Prime 2. Unknown in Prime 3.
15	0x00000000 00008000	Unused4	Unused in Prime 2. Unknown in Prime 3.
16	0x00000000 00010000	Shield	Shield surface type. Generally used on collision for force fields.
17	0x00000000 00020000	Sand	Sand surface type.
18	0x00000000 00040000	Moth Organics/Seed Organics	Alternate organic surface type; used for moth materials in Prime 2 and used in the Leviathan Core rooms in Prime 3.
19	0x00000000 00080000	Web	Spider web surface type.
20	0x00000000 00100000	Shoot Thru	If this flag is enabled, projectiles can pass through this surface. (Presumably has no effect unless projectiles are configured to use the collision geometry instead of the render geometry.)
21	0x00000000 00200000	Camera Thru	If this flag is enabled, the morph ball camera can pass through this surface.
22	0x00000000 00400000	Wood	Wood surface type.
23	0x00000000 00800000	Organic	Organic surface type.
24	0x00000000 01000000	Redundant Edge/Flipped Tri	Triangles with this flag enabled are flipped around.
25	0x00000000 02000000	Rubber	Rubber surface type.
26	0x00000000 04000000	See Thru	Indicates this surface is an invisible wall. Unknown function.
27	0x00000000 08000000	Scan Thru	If this flag is enabled, this surface doesn't block lock-ons in any visor.
28	0x00000000 10000000	AI Walk Thru	If this flag is enabled, AI actors can pass through this surface.
29	0x00000000 20000000	Ceiling	Indicates this surface is a ceiling.
30	0x00000000 40000000	Wall	Indicates this surface is a wall.
31	0x00000000 80000000	Floor	Indicates this surface is a floor.
32	0x00000001 00000000	Player (Internal)	Internal use only.
33	0x00000002 00000000	Character (Internal)	Internal use only.
34	0x00000004 00000000	Trigger (Internal)	Internal use only.
35	0x00000008 00000000	Projectile (Internal)	Internal use only.
36	0x00000010 00000000	Bomb (Internal)	Internal use only.
37	0x00000020 00000000	Ground Collider (Internal)	Internal use only.
38	0x00000040 00000000	No Static World Collision (Internal)	Internal use only.
39	0x00000080 00000000	Scannable (Internal)	Internal use only.
40	0x00000100 00000000	Target (Internal)	Internal use only.
41	0x00000200 00000000	Orbit (Internal)	Internal use only.
42	0x00000400 00000000	Occluder (Internal)	Internal use only.
43	0x00000800 00000000	Immovable (Internal)	Internal use only.
44	0x00001000 00000000	Debris (Internal)	Internal use only.
45	0x00002000 00000000	Power Bomb (Internal)	Internal use only.
46	0x00004000 00000000	Targetable Projectile (Internal)	Internal use only.
47	0x00008000 00000000	Collision Only Actor (Internal)	Internal use only.
48	0x00010000 00000000	AI Block (Internal)	Internal use only.
49	0x00020000 00000000	Platform (Internal)	Internal use only.
50	0x00040000 00000000	Non Solid Damageable (Internal)	Internal use only.
51	0x00080000 00000000	Show on Radar (Internal)	Internal use only.
52	0x00100000 00000000	Platform Slave (Internal)	Internal use only.
53	0x00200000 00000000	No Ice Spread (Internal)	Internal use only.
54	0x00400000 00000000	Grapple Thru (Internal)	Internal use only.
55	0x00800000 00000000	Can Jump on Character (Internal)	Internal use only.
56	0x01000000 00000000	Exclude from Line of Sight Test (Internal)	Internal use only.
57	0x02000000 00000000	Don't Show on Radar (Internal)	Internal use only.
58	0x04000000 00000000	Jump Not Allowed	If this flag is enabled, the player won't be able to stand on this surface and instead will slide off it.
59	0x08000000 00000000	Solid (Internal)	Internal use only.
60	0x10000000 00000000	Complex (Internal)	Internal use only.
61	0x20000000 00000000	Spider Ball	If this flag is enabled, the player will be able to use Spider Ball on this surface. This is used for irregularly-shaped spider ball attraction surfaces (like spheres).
62	0x40000000 00000000	Screw Attack Wall Jump	If this flag is enabled, the player can wall jump from this wall using Screw Attack.
63	0x80000000 00000000	Seek (Internal)	Internal use only.

Donkey Kong Country Returns

Bit	Hex	Name	Description
0	0x00000000 00000001	Unknown
1	0x00000000 00000002	Unknown
2	0x00000000 00000004	Unknown
3	0x00000000 00000008	Unknown
4	0x00000000 00000010	Unknown
5	0x00000000 00000020	Unknown
6	0x00000000 00000040	Unknown
7	0x00000000 00000080	Unknown
8	0x00000000 00000100	Ceiling	Indicates this surface is a ceiling.
9	0x00000000 00000200	Wall	Indicates this surface is a wall.
10	0x00000000 00000400	Floor	Indicates this surface is a floor.
11	0x00000000 00000800	Player Walk Thru	If this flag is enabled, the player can pass through this surface.
12	0x00000000 00001000	Unknown
13	0x00000000 00002000	Unknown
14	0x00000000 00004000	AI Walk Thru	If this flag is enabled, AI actors can pass through this surface.
15	0x00000000 00008000	Unknown
16	0x00000000 00010000	Unknown
17	0x00000000 00020000	Unknown
18	0x00000000 00040000	Unknown
19	0x00000000 00080000	Unknown
20	0x00000000 00100000	Unknown
21	0x00000000 00200000	Unknown
22	0x00000000 00400000	Unknown
23	0x00000000 00800000	Unknown
24	0x00000000 01000000	Unknown
25	0x00000000 02000000	Unknown
26	0x00000000 04000000	Unknown
27	0x00000000 08000000	Unknown
28	0x00000000 10000000	Redundant Edge/Flipped Tri	Triangles with this flag enabled are flipped around.
29	0x00000000 20000000	Unknown
30	0x00000000 40000000	Unknown
31	0x00000000 80000000	Unknown
32	0x00000001 00000000	Unknown
33	0x00000002 00000000	Unknown
34	0x00000004 00000000	Unknown
35	0x00000008 00000000	Unknown
36	0x00000010 00000000	Unknown
37	0x00000020 00000000	Unknown
38	0x00000040 00000000	Unknown
39	0x00000080 00000000	Unknown
40	0x00000100 00000000	Unknown
41	0x00000200 00000000	Unknown
42	0x00000400 00000000	Unknown
43	0x00000800 00000000	Unknown
44	0x00001000 00000000	Unknown
45	0x00002000 00000000	Unknown
46	0x00004000 00000000	Unknown
47	0x00008000 00000000	Unknown
48	0x00010000 00000000	Unknown
49	0x00020000 00000000	Unknown
50	0x00040000 00000000	Unknown
51	0x00080000 00000000	Unknown
52	0x00100000 00000000	Unknown
53	0x00200000 00000000	Unknown
54	0x00400000 00000000	Unknown
55	0x00800000 00000000	Unknown
56	0x01000000 00000000	Unknown
57	0x02000000 00000000	Unknown
58	0x04000000 00000000	Unknown
59	0x08000000 00000000	Unknown
60	0x10000000 00000000	Unknown
61	0x20000000 00000000	Unknown
62	0x40000000 00000000	Unknown
63	0x80000000 00000000	Unknown