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 is almost completely documented Discounting unknowns within the actual data sections, the main thing that still isn't known is what the unknown data section is for.

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.

These are the sections that appear in each MREA file, in the order they appear in the file:

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

Header

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	Data Section Count	Number of data sections in the file.
0x40	u32	1	World Geometry Section	Section index for world geometry data. Always 0; starts on materials.
0x44	u32	1	Script Layers Section	Section index for script layer data.
0x48	u32	1	Collision Section	Section index for collision data.
0x4C	u32	1	Unknown Section	Section index for unknown data.
0x50	u32	1	Lights Section	Section index for light data.
0x54	u32	1	Visibility Tree Section	Section index for visibility tree data.
0x58	u32	1	Path Section	Section index for path data.
0x5C	u32	1	Area Octree Section	Section index for area octree data.
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 header; pad to 32 bytes before first data section begins

World Geometry

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

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

• Normals are always shorts, so vertex format 0 is never used.
• Most world models 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 world model starts with an extra header section which is formatted like this:

Offset	Type	Count	Name	Notes
0x0	Visor Flags	1	Visor Flags	32-bit bitfield that sets parameters controlling how the mesh renders in different visors.
0x4	float	12	World Model Transform	World model's transform from the area's local origin. The geometry data is pre-transformed, so this matrix can largely be ignored.
0x34	float	6	World Model Bounding Box	Pre-transformed axis-aligned bounding box for this model.
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.