MREA (Metroid Prime 3)

Revision as of 04:03, 4 April 2015 by imported>Jackoalan

The .MREA file format is used to define areas in Metroid Prime 3 and Donkey Kong Country Returns. MREA files are broken up into many sections, and each section serves a specific purpose.

This file format needs more research
Still a few sections we know nothing about.

Universal Header

This header is shared between Metroid Prime and Donkey Kong Country, and is fairly straight forward.

Offset Size Description
0x0 4 Magic Number 0xDEADBEEF
0x4 4 Version; see hub article
0x8 48 Transformation Matrix The position of the area in world-space
0x38 4 Mesh Count
0x3C 4 SCLY Count
0x40 4 Section Count
0x0 4 Compressed Block Count
0x4 4 Section Number Count

Compressed Blocks

Compressed blocks are handled in the exact same manner as Metroid Prime 2, however with DKCR simply replace LZO with zlib.

Section Numbers

Section Numbers are preceded by the compressed blocks, each section is designated in the following:

let N=Section Number Count

Type Description
FourCC Section type
Long Section Number

Repeat N times, one for each section, and the sections sections are associated with the following FourCC values:


FourCC Description
AABB Axis Aligned Bounding Boxes
APTL Unknown
COLI Collision
DEPS Dependencies
EGMC Unknown
GPUD Submesh data, e.g, vertices, normals, etc.
LITE Lights
LLTE Unknown
PFL2 Path file
PVS! Area vis octree, used for culling unseen geometry
ROCT Unknown
RSOS Revolution Shared Objects
SOBJ SCLY Layer data, there can be multiple copies, but only the first is indicated.
SGEN Unknown
WOBJ Mesh Header, always 0, the number of WOBJ sections is determined by the mesh count in the header.

Sections

Materials

Materials are identical to those found in CMDL files.

Mesh Headers

The WOBJ sections are unique: they don't have a valid section number, and are always set to 0, however they are always in the sections immediately following the Materials, simply iterate through the mesh count and read the following structs:

Main Header

Type Description Notes
long Unknown Most likely visor flags in MP3, unknown use and DKCR
CTransform4f Transformation Matrix Meshes location in world space
CAABox Bounding Box Likely used for Depth sorting as in previous games.

Submesh Offsets

Type Description Notes
long (SC) Submesh count
long Submesh Offsets[SC] Relative to the start first submesh, (i.e, the first offset points the the end of the first submesh)

Following the submesh data are two unknown sections, they both seem to be arrays of flags or indices but nothing is known about them.

AROT

Following the WOBJ sections is usually AROT. AROT is a BSP Tree that appears to be used for shot-collision and possibly depth sorting, nothing is known about how to handle this section.

AABB

The AABB section is exactly what it sounds like, it's an array of Axis-Aligned Bounding Boxes, assembling a BVH tree. AABB starts with the number of bounding boxes with each one consisting of the following struct:

Type Description Notes
CAABox Axis Aligned Bounding Box Used to assist depth sorting, and/or collision
long Unknown The first entry in the table always covers the entire, with this value always being -1
short Self Index 1 indexed position of this particular AABB entry, but ONLY if the previous value is -1.
short Self Index 1 indexed position of this particular AABB entry, but ONLY if the previous value is -1.

GPU Description Section (GPUD)

The GPUD section is a bit confusing at first glance, however it's really no different from the previous MREA version in terms of ordering. There is also one GPUD per WOBJ section

The section order is as follows:

Vertices

The vertices are always 32bit floats, even in DKCR

Normals

The normals are always 32bit floats.

Colors

Usually 0 filled and completely unused, it's stored in MREA simply for completeness.

Float Texcoords

Metroid Prime 3 uses these exclusively, even for lightmaps, which simplifies UV handling quite a bit.

Short Texcoords

This is only used in DKCR and can be used for anything, not just for lightmaps

Submeshes

The submesh format is exactly the same as the Geometry formats found in Metroid Prime 3 and DKCR.