MREA (Metroid Prime)

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

The MREA format defines areas (rooms) in Metroid Prime. It's a massive format that contains tons of different data, including terrain geometry, collision, objects, lights, and more.

To do:
There's a LOT of sections that are mostly known, but need some documentation written up. SCLY and collision need separate articles (although the unique parts of the collision format, like the octree, could maybe be documented here). The rest should probably stay on this page.

This file format needs more research
There's a lot of unknowns in the lights section, and we don't know what the unknown/empty sections are for. That's not even touching on how much is unknown in SCLY.

Format

Like CMDL, 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

Offset	Size	Description
0x0	4	Magic; always 0xDEADBEEF
0x4	4	Version; see hub article
0x8	4 × 12	Transform matrix
0x38	4	Mesh count
0x3C	4	Section count (SC)
0x40	4	Geometry section number (starts on materials)
0x44	4	SCLY section number
0x48	4	Collision section number
0x4C	4	Unknown section number
0x50	4	Light section number
0x54	4	VISI section number
0x58	4	PATH section number
0x5C	4	AROT section number
0x60	4 × SC	Section sizes
End of header; pad to 32 bytes before first section begins

Data Sections

MREA data sections are in the file in the following order:

Identifier	Name
	Geometry
`AROT`	Area Octree
`SCLY`	Script Layers
`0xDEAFBABE`	Collision
	Unknown
`0xBABEDEAD`	Lights
`VISI`	Visibility Tree
	Path

Geometry

See Materials (Metroid Prime) and Geometry (Metroid Prime)

MREA files have one material section, followed by a number of meshes, each of which has its own set of geometry sections. There's couple small differences you'll usually see on MREA meshes compared to CMDL ones:

Normals are always shorts, so vertex format 0 is never used.
Most MREA meshes use lightmaps, so normally the first UV coordinate on each vertex will read from the short UV array. This isn't always the case, though; you need to make sure you check the material so you know where to read from.
Surfaces will usually have a bounding box in the extra data in the surface header. This bounding box is used for depth sorting.
Each mesh starts with an extra header section which is formatted like this:

Offset	Size	Description
0x0	4	Visor Flags
0x4	4 × 12	Transform matrix
0x34	4 × 6	Axis-aligned bounding box
0x4C	End of mesh header section

Visor Flags

Bit	Hex	Description
0	0x1	Unknown
1	0x2	Disable rendering in Combat/Scan Visor
2	0x4	Disable rendering in Thermal Visor
3	0x8	Disable rendering in X-Ray Visor
4-5	0x30	Thermal heat level. 0 - Cool 1 - Hot 2 - Warm

Area Octree

Main article: AROT (MREA Section)

The AROT section stores the area's octree, accelerating back-to-front rendering of contained meshes, it is also used for spacial queries such as collision.

Script Layers

To do:
SCLY is definitely complicated enough to need its own article.

The SCLY section contains data for objects.

Collision

To do:
Collision needs a separate article because it shares so many similarities with DCLN. How should we document the parts where the format diverges, though?

You have three guesses what the collision section is for, and the first two don't count.

Unknown Section

This one is sandwiched between collision and lights, and usually just contains a single 32-bit "1". Purpose is unknown.

Lights

This section is for dynamic lights, see the Light article for details.

Visibility Tree

This section is labeled "VISI". This section is sometimes not actually present in the file, labeled with a size of 0.

Path

This is the final section in the file; it's always 0x20 bytes, and its only value is a single PATH file ID.

Tools

Parax's MREA maxscript can import MREA terrain geometry into 3DS Max.