MLVL (File Format)

The MLVL format defines worlds in the Metroid Prime trilogy and Donkey Kong Country Returns. While the MREA format defines individual areas, the MLVL is what links together all the areas to create a single cohesive world.

This file format is almost completely documented
There's a couple unknown values in this format, but they all seem to have constant values.

Format

The format largely defines properties related to each area in general and how they link together, as well as things that apply to the world on a global scale across all areas, such as the skybox.

Type	Count	Name	Notes	MP1	MP2	MP3	DKCR
u32	1	Magic	Always `0xDEAFBABE`	✔	✔	✔	✔
u32	1	Version	See below	✔	✔	✔	✔
Asset ID (STRG)	1	World Name ID	STRG file for the world name.	✔	✔	✔	✔
Asset ID (STRG)	1	Dark World Name ID	STRG file for the Dark World name.	✖	✔	✖	✖
u32	1	Temple Key World Index	Controls which temple key icons appear on the map screen. Appears in Prime 3 but always 0.	✖	✔	✔	✖
bool	1	Has Time Attack	Indicates whether this world has a Time Attack mode. If false, the next five values are not present.	✖	✖	✖	✔
string	1	Level Number	String of the world/level number; for example, "1-1". Purpose unknown.	✖	✖	✖	✔
float	1	Time Attack Bronze Time	Target time for a bronze medal in Time Attack.	✖	✖	✖	✔
float	1	Time Attack Silver Time	Target time for a silver medal in Time Attack.	✖	✖	✖	✔
float	1	Time Attack Gold Time	Target time for a gold medal in Time Attack.	✖	✖	✖	✔
float	1	Time Attack Shiny Gold Time	Target time for a shiny gold medal in Time Attack.	✖	✖	✖	✔
Asset ID (SAVW)	1	World Save Info ID	Asset ID for this world's SAVW file.	✔	✔	✔	✔
Asset ID (CMDL)	1	Default Skybox ID	CMDL file for this world's default skybox model. This can be overridden per-area by AreaAttributes objects.	✔	✔	✔	✔
u32	1	Memory Relay Count	Count of all outgoing connections from Memory Relay instances in this world.	✔	✖	✖	✖
Memory Relay	Memory Relay Count	Memory Relay Array	Array describing all outgoing Memory Relay connections in this world. Memory Relays connected to multiple objects are listed multiple times.	✔	✖	✖	✖
u32	1	Area Count	Count of areas in this world.	✔	✔	✔	✔
u32	1	Unknown	Always 1?	✔	✖	✖	✖
Area	Area Count	Area Array	Array defining all areas that appear in this world.	✔	✔	✔	✔
Asset ID (MAPW)	1	World Map ID	ID of this world's MAPW file.	✔	✔	✔	✖
u8	1	Unknown	This is presumably the same unknown value as at the beginning of the SCLY format. Always 0.	✔	✔	✔	✖
u32	1	Script Instance Count	The MLVL format embeds a script layer. This script layer is used in the MP1 demo for storing Dock instances, but it's unused in all retail builds, so this is always 0.	✔	✔	✔	✖
u32	1	Audio Group Count	Count of all audio groups used in this world.	✔	✖	✖	✖
Audio Group	Audio Group Count	Audio Group Array	Array describing all audio groups used in this world.	✔	✖	✖	✖
string	1	Unknown	Always empty, so the only value that ever appears here is the terminating 0.	✔	✖	✖	✖
u32	1	Area Count	Will be equal to the earlier area count.	✔	✔	✔	✔
Area Layer Flags	Area Count	Area Layer Flags	This array initializes the default active state for all script layers in each area.	✔	✔	✔	✔
u32	1	Layer Name Count	Count of layer names in the next array.	✔	✔	✔	✔
string	Layer Name Count	Layer Name Array	Array of all layer names in the world.	✔	✔	✔	✔
u32	1	Layer State ID Count	Count of layer state IDs in the next array.	✖	✖	✔	✔
Saved State ID	Layer State ID Count	Layer State ID Array	Array of saved state IDs for each layer. These IDs are responsible for storing the layer's active state in the save file and are referenced by ScriptLayerController objects.	✖	✖	✔	✔
u32	1	Area Count	Identical to the previous two area counts.	✔	✔	✔	✔
u32	Area Count	Area Layer Name Offset Array	Each value is an offset into the layer name array and points to where the layer names for each area begins.	✔	✔	✔	✔
End of file

Version

These are the known version numbers:

ID	Game
0xD	Metroid Prime Demo
0x11	Metroid Prime
0x14	Metroid Prime 2 Demo
0x17	Metroid Prime 2
0x19	Metroid Prime 3
0x1B	Donkey Kong Country Returns

Memory Relay

This structure only appears in Prime 1. It describes an outgoing connection from a Memory Relay to another script instance. Any Memory Relays connected to multiple objects will appear in the array multiple times.

Offset	Type	Name	Notes
0x0	u32	Memory Relay Instance ID	Instance ID of the sender Memory Relay.
0x4	u32	Target Instance ID	Instance ID of the receiver object.
0x8	u16	Message	Script message sent to the receiver object.
0x10	bool	Active	Whether this Memory Relay object is active by default; almost always 0.
0x11	End of Memory Relay connection

Area

This structure defines a single area and describes its position in the world and how it connects to other areas.

Type	Count	Name	Notes	MP1	MP2	MP3	DKCR
Asset ID (STRG)	1	Area Name ID	STRG ID for the area name.	✔	✔	✔	✔
float	12	Area Transform	Area's transform matrix. Most area data is pre-transformed, but there are a few things that need to be transformed by this matrix.	✔	✔	✔	✔
float	6	Area Bounding Box	This is the bounding box of the area's collision mesh and is equivalent to the bounding box found in the MREA collision section.	✔	✔	✔	✔
Asset ID (MREA)	1	Area MREA ID	ID of this area's MREA file.	✔	✔	✔	✔
Asset ID	1	Internal Area ID	Doesn't actually refer to an asset, but has the same length as an asset ID. This ID is used internally by some things to refer to this area, such as Script Layer Controllers.	✔	✔	✔	✔
u32	1	Attached Area Count	Count of areas attached to this one.	✔	✔	✔	✖
u16	Attached Area Count	Attached Area Index Array	Array of area indices attached to this one.	✔	✔	✔	✖
Area Dependencies	1	Dependencies	Asset dependencies in this area. See below for details. Starting in Prime 3, this section has been moved inside the MREA file.	✔	✔	✖	✖
u32	1	Dock Count	Count of Dock instances in this area. Should be equal to the attached area count.	✔	✔	✔	✖
Dock	Dock Count	Dock Array	Array describing all docks in this area.	✔	✔	✔	✖
Area Module Dependencies	1	Module Dependencies	REL module dependencies in this area. See below for details. The equivalent section in Prime 3 and DKCR describing RSO modules has been moved inside the MREA format.	✖	✔	✖	✖
u32	1	Unknown	Always 0?	✖	✖	✖	✔
string	1	Internal Area Name	Internal name of this area. Does not appear ingame.	✖	✔	✔	✔
End of area

Area Dependencies

This is a data chunk appearing in the area definition in Metroid Prime 1 and 2 that lists all assets needed to load the area. It's extremely important that this list be optimized and complete, as all assets listed here will be perpetually kept in memory as long as the area itself is in memory; the list also specifies the order that assets are loaded in, so it must be grouped by load order to roughly match the PAK file for optimized load times. Assets that are missing will still be dynamically loaded after the area itself is loaded, but this will cause the game to freeze up until the load is finished. There are a few exceptions that are excluded from this list in the original game files (and should be excluded in custom MLVLs as well to avoid out-of-memory crashes):

SCAN files and their dependencies are not included in the list. These are loaded dynamically after the area itself is finished loading.
ANCS per-character dependencies for PlayerActor script instances are not included; this allows the game to avoid keeping assets in memory for suits that the player doesn't have. The exception is the Empty Suit character (character index 5), which is a low-memory-overhead character that allows for the list to include all common assets that are stored in the file per-character (such as particle effects).
The skybox model and its dependencies are not included.

The dependency list is split by layer; after the dependencies itself, an array of offsets into the dependency list is provided that allows the game to only load assets for layers that are currently active. The last offset points to all common resources used by the area that aren't layer-specific. With that in mind, every layer needs to have a full list of its required assets even if they're also used by other layers. There's no harm in including an asset multiple times, as if an asset is already in memory then it'll simply be skipped over.

This data chunk still exists in Prime 3 and DKCR, but it's been moved inside the MREA format.

Type	Count	Name	Notes
u32	1	Dependency Count	Count of dependencies.
Dependency	Dependency Count	Dependency Array	Array of all asset dependencies in this area.
u32	1	Dependency Offset Count	Count of dependency offsets. This will be equal to the area script layer count + 1.
u32	Dependency Offset Count	Dependency Offset Array	Array of offsets into the dependency array. There is one offset per script layer, with the offset referring to the index of that layer's first dependency. There is a final extra offset that points to area dependencies that are not layer-specific.

Dependency

Offset	Type	Count	Name
0x0	Asset ID	1	Dependency Asset ID
0x4	char	4	Dependency Asset Type

Dock

Type	Count	Name	Notes
u32	1	Connecting Dock Count	Count of docks connecting to this one. Typically 1 (but there are docks in Prime 3 that connect to multiple areas).
Connecting Dock	Connecting Dock Count	Connecting Dock Array	Array describing all docks connected to this one.
u32	1	Dock Coordinate Count	Array of dock coordinates in the next array.
Vector3	Dock Coordinate Count	Dock Coordinates	Exact purpose/function of this is not known yet.

Connecting Dock

Offset	Type	Name	Notes
0x0	u32	Area Index	Index of the area this dock is in.
0x4	u32	Dock Index	Index of this dock within its area.

Area Module Dependencies

This is a data chunk appearing in the area definitions that describes all REL modules that must be linked in for this area to run. These are tied to script objects. The list is split per-layer so that only modules being used by the active layer are linked in; modules will appear once in the list for each layer that uses it. After the REL list, there is an array of offsets that points to the starting index in the list for each script layer, similar to the regular area dependencies list. For an unknown reason, the offsets list contains two offsets per layer. The first one refers to the layer's start index while the second one is usually empty, which effectively makes it an end index.

Type	Count	Name	Notes
u32	1	REL Module Count	Count of REL modules in the next array.
string	REL Module Count	REL Module Array	REL modules used by this area. Each array entry is the filename of a .REL module.
u32	1	REL Offset Count	Count of REL offsets in the next array. Should be equal to the area script layer count * 2.
u32	REL Offset Count	REL Offset Array	Array of offsets into the REL Module Array. There are two offsets per script layer, with the first one being that layer's start index and the second one effectively being that layer's end index.

Audio Group

This structure is only present in Prime 1 and describes an AGSC file being used in this world.

Offset	Type	Name	Notes
0x0	u32	Group ID	Group ID for this audio group. This is the same value that can be found in the Project chunk in the referenced AGSC file.
0x4	Asset ID (AGSC)	AGSC ID	The AGSC file for this audio group.
0x8	End of audio group definition

Area Layer Flags

This is a small structure that determines which areas are active by default. It contains a layer count and then a 64-bit flag, with each bit corresponding to a particular layer; if the bit is set, then the layer will be active on a new save file. The low-order bits correspond to the lower layer indices. Bits for layers that don't exist are defaulted to on.

Note that due to the size of these flags as well as a few other pieces of data in other formats, the maximum number of layers that can be contained in a single area is 64.

Offset	Type	Name	Notes
0x0	u32	Layer Count	Count of layers in this area.
0x4	u64	Layer Flags	See above for a description of how these work.
0x8	End of area layer flags