MREA (Metroid Prime 3)

See MREA (File Format) for the other revisions of this format.

The MREA format, which defines areas/levels, received another large layout overhaul in Metroid Prime 3. The level geometry data received the biggest update, with a new material format, lot of things being moved around, and a few entirely new sections being introduced. This article covers Metroid Prime 3, the MP3 E3 prototype, and Donkey Kong Country Returns.

This file format needs more research
Research needed on the area octree and visibility tree sections to verify structure and check for version differences. Also the purpose of the LLTE section is unknown.

Format

MREA files are split up into a number of 32-byte aligned sections. Every section both starts and ends on a 32-byte boundary. These are used to separate different parts of the file; different types of sections typically indicate different sets of data. The header declares the section count and the size of each one; using these is the only way to navigate the file.

Header

The header is identical between MP3 and DKCR.

Offset	Type	Count	Name	Notes
0x0	u32	1	Magic	Always `0xDEADBEEF`.
0x4	u32	1	Version	See hub article for a list of possible version numbers.
0x8	float	12	Area Transform	Matrix that represents the area's transform from the origin. Most area data is pre-transformed, so this matrix is only used occasionally.
0x38	u32	1	World Model Count	Number of world models in this area.
0x3C	u32	1	Script Layer Count	Number of script layers in this area.
0x40	u32	1	Data Section Count	Number of data sections in the file.
0x44	u32	1	Compressed Block Count	Number of compressed data blocks in the file.
0x48	u32	1	Section Number Count	Number of section numbers at the end of the header.
0x4C	u32	5	Padding	Padding bytes that align the file with the next multiple-of-32 offset.
0x60	u32	Data Section Count	Data Section Sizes	Array containing the size of each data section in the file. Every size is always a multiple of 32.
End of main header data; pad to 32 bytes before compressed section definitions

Compressed Blocks

Compressed blocks are defined in the same manner as Metroid Prime 2. The MREA format contains compressed blocks that can each contain a number of regular file sections within them. These blocks are compressed using segmented LZO1X-999 in Metroid Prime 3, and segmented zlib in Donkey Kong Country Returns. Compressed blocks are padded to 32 bytes, but their padding is located at the beginning of the block rather than the end, so it's required to account for the padding before you start decompressing. The compressed data is segmented, which means there's multiple segments of data that are compressed/decompressed separately. Each segment starts with a 16-bit size value. The size value is signed; a negative value indicates the segment is not compressed (this is done when compressing a segment doesn't reduce its size). Each segment is 0x4000 bytes large when decompressed (except the last one).

Compressed blocks are defined after the main header. After reading them, pad to 32 bytes before the section numbers portion of the header starts.

Offset	Type	Count	Name	Notes
0x0	u32	1	Buffer Size	This is always 0x120 bytes larger than the uncompressed size on compressed bytes, and the same value as the uncompressed size on uncompressed blocks
0x4	u32	1	Uncompressed Size
0x8	u32	1	Compressed Size	This is 0 on uncompressed blocks.
0xC	u32	1	Data Section Count	The number of regular data sections contained in this block.
0x10	Block definition end

Section Numbers

The section numbers portion of the header indicates the section index of each major data chunk. Some of these chunks contain multiple sections; in that case the number will point to the first section of the chunk. Each number is a short 8-byte struct:

Offset	Type	Count	Name
0x0	char	4	Section Type
0x4	u32	1	Section Index

WOBJ can be listed multiple times, but its section index is always 0 (pointing to the materials section). Every other section number always appears in every MREA file once (none are optional). Here are all possible section numbers and what they are, in the order that they appear in the file:

FourCC	Description	MP3	DKCR
`WOBJ`	Materials + World Model Definition	✔	✔
`ROCT`	Area Octree	✔	✔
`AABB`	Surface Group Bounding Boxes	✔	✔
`GPUD`	World Geometry GPU Data	✔	✔
`DEPS`	Dependencies	✔	✔
`SOBJ`	Script Layers	✔	✔
`SGEN`	Generated Script Objects	✔	✔
`COLI`	Collision	✔	✔
`LITE`	Lights	✔	✔
`LLTE`	Unknown	✔	✔
`PVS!`	Visibility Tree	✔	✔
`RSOS`	RSO Module List	✔	✔
`PFL2`	Path	✔	✖
`APTL`	Portal Area	✔	✖
`EGMC`	Static Geometry Map	✔	✖

Materials

See Materials (Metroid Prime 3)

Identical to the material format found in CMDL. There is just one materials section which is shared across all world models.

World Model Definition

The world geometry definitions always appear immediately following the materials section. Each definition is a sequence of four sections. All four of these sections are identical to their structure in the previous MREA formats in both MP3 and DKCR, so check those pages:

Area Octree

See AROT (MREA Section)

Surface Group Bounding Boxes

See MREA (Metroid Prime 2)#Surface Group Bounding Boxes

GPU Data

This section contains the GPU buffer data used to render world geometry. This is generally the same as in previous games, with the following sequence of sections repeated once per world model:

Vertices: Always floats; world geometry vertices are never packed into shorts.
Normals: Always floats; world geometry normals are never packed into shorts.
Colors: Contains 32-bit RGBA8 colors. This section is not used in any official assets and is always zeroed out.
Float UV Coordinates: In Metroid Prime 3, this is the only UV coordinates section, so it's used for everything.
Short UV Coordinates: Only appears in Donkey Kong Country Returns; can be used for anything, not only lightmaps as in previous games.
Surfaces: One section per surface. For details on the structure of these sections check Geometry (Metroid Prime) page for MP3 and the Geometry (Donkey Kong Country Returns)page for DKCR.

Dependencies

This file format is almost completely documented
How does this section work with SCGN?

This section is basically a list of all resources that this area depends on, not unlike a DGRP file. After the initial dependency list, there's a second array which provides a list of offsets into the dependency list. These offsets are used to indicate which dependencies are needed for individual script layers, with the last offset pointing to resources that are used by the area itself as a whole (world geometry textures and the PATH/PTLA/EGMC assets).

Type	Count	Name	Notes
u32	1	Dependency Count	Count of dependencies in the next array.
Dependency	Dependency Count	Dependency List	List of resources used by this area.
u32	1	Offset Count	Count of offsets in the next array. Should be equal to the script layer count + 1.
u32	Offset Count	Dependency List Offsets	Each element is an offset into the dependency list to indicate where the dependencies for individual script layers begins. There's one offset per script layer, then the last offset points to resources used by the area itself outside of script layers.
End of dependencies section

Dependency

Offset	Type	Count	Name
0x0	Asset ID	1	Dependency Asset ID
0x8	char	4	Dependency Asset Type
0xC	End of dependency

Script Layers

To do:
This section is known, needs documentation written

Generated Script Objects

To do:
Almost identical to script layers but there are some slight differences in the header

This section is an extra script layer that contains generated objects (anything spawned by a Generator).

Collision

To do:
This section is known, needs documentation written

Lights

See Lights (Metroid Prime)

Unknown Section (LLTE)

This section always contains just a single 32-bit 1. It doesn't appear to do anything, so the purpose of this section is unknown.

Visibility Tree

This file format needs a lot of research
This section is largely unknown

RSO Module List

This section is a list of RSO modules used by script objects in the area. Like the dependencies section, there's also a list of offsets to indicate which RSOs are used by each script layer.

Type	Count	Name	Notes
u32	1	RSO Count	Count of RSO modules listed in the next array.
string	RSO Count	RSO Module List	This is a series of zero-terminated strings. Each string is the filename of a .rso file.
u32	1	Offset Count	Count of offsets in the next array. Should be equal to the script layer count * 2.
u32	Offset Count	RSO Module List Offsets	Each element is an offset into the RSO module list to indicate which modules are required by each script layer. For some reason there are two offsets per script layer.
End of RSOs section

Path

This section only contains a single PATH asset ID.

Type	Count	Name
Asset ID	1	Area PATH Resource
End of section

Portal Area

This section only contains a single PTLA asset ID.

Type	Count	Name
Asset ID	1	Area PTLA Resource
End of section

Static Geometry Map

This section only contains a single EGMC asset ID.

Type	Count	Name
Asset ID	1	Area EGMC Resource
End of section

MREA (Metroid Prime 3)

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