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This document describes the Quake 3 BSP file format. This is an unofficial document. Quake 3 is a registered trademark of id Software, which does not sponsor, authorize, or endorse this document.
This document describes the Quake 3 BSP file format as the author understands it. While every effort has been made to ensure that the contents of this document are accurate, the author does not guarantee that any portion of this document is actually correct. In addition, the author cannot be held responsible the consequences of the any use or misuse of the information contained in this document.
Copyright © 2000 Kekoa Proudfoot. All rights
reserved.
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File structure
Quake 3 BSP files are IBSP files, and therefore have a structure similar to previous BSP files from id Software. Every IBSP file begins with a header, which in turn contains a lump directory. The lump directory describes the layout of the rest of the file, which contains some number of lumps. Each lump stores a particular kind of map data.
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| The layout of an IBSP file. An IBSP file consists of a header followed by a number of lumps. The header contains a directory which identifies the locations and sizes of the lumps. |
Data types
Quake 3 BSP files contains only four basic data types. They are:
| Type | Description |
|---|---|
| ubyte | unsigned byte |
| int | 4-byte integer, little-endian |
| float | 4-byte IEEE float, little-endian |
| string[n] | string of n ASCII bytes, not necessarily null-terminated |
All data in a BSP file is organized into records composed of these four data
types.
Header and Directory
The header record looks like this:
header
Each direntry locates a single lump in the BSP file:
direntry
Lumps
There are 17 lumps in a Quake 3 BSP file. In the order that they
appear in the lump directory, they are:
string[4] magic
Magic number. Always "IBSP".
int version
Version number. 0x2e for the BSP files distributed with Quake 3.
direntry[17] direntries
Lump directory, seventeen entries.
int offset
Offset to start of lump, relative to beginning of file.
int length
Length of lump. Always a multiple of 4.
| Index | Lump Name | Description |
|---|---|---|
| 0 | Entities | Game-related object descriptions. |
| 1 | Textures | Surface descriptions. |
| 2 | Planes | Planes used by map geometry. |
| 3 | Nodes | BSP tree nodes. |
| 4 | Leafs | BSP tree leaves. |
| 5 | Leaffaces | Lists of face indices, one list per leaf. |
| 6 | Leafbrushes | Lists of brush indices, one list per leaf. |
| 7 | Models | Descriptions of rigid world geometry in map. |
| 8 | Brushes | Convex polyhedra used to describe solid space. |
| 9 | Brushsides | Brush surfaces. |
| 10 | Vertexes | Vertices used to describe faces. |
| 11 | Meshverts | Lists of offsets, one list per mesh. |
| 12 | Effects | List of special map effects. |
| 13 | Faces | Surface geometry. |
| 14 | Lightmaps | Packed lightmap data. |
| 15 | Lightvols | Local illumination data. |
| 16 | Visdata | Cluster-cluster visibility data. |
Entities
The entities lump stores game-related map information, including information about the map name, weapons, health, armor, triggers, spawn points, lights, and .md3 models to be placed in the map. The lump contains only one record, a string that describes all of the entities:
entities
string[length] ents Entity descriptions, stored as a string.
The length of the entity string is given by the size of the lump itself, as specified in the lump directory.
The meanings, formats, and parameters of the various entity descriptions
are currently outside the scope of this document. For more information
about entity descriptions, see the documentation to Q3Radiant, the Quake 3
level editor.
Textures
The textures lump stores information about surfaces and volumes, which are
in turn associated with faces, brushes, and brushsides. There are a total
of length / sizeof(texture) records in the lump, where
length is the size of the lump itself, as specified in the lump
directory.
texture
Planes
The planes lump stores a generic set of planes that are in turn referenced
by nodes and brushsides. There are a total of length /
sizeof(plane) records in the lump, where length is the size
of the lump itself, as specified in the lump directory.
plane
Note that planes are paired. The pair of planes with
indices i and i ^ 1 are coincident planes with opposing normals.
Nodes
The nodes lump stores all of the nodes in the map's BSP tree. The BSP tree
is used primarily as a spatial subdivision scheme, dividing the world into
convex regions called leafs. The first node in the lump is the tree's root
node. There are a total of length / sizeof(node) records
in the lump, where length is the size of the lump itself, as
specified in the lump directory.
node
Leafs
The leafs lump stores the leaves of the map's BSP tree. Each leaf is a
convex region that contains, among other things, a cluster index (for
determining the other leafs potentially visible from within the leaf), a
list of faces (for rendering), and a list of brushes (for collision
detection). There are a total of length / sizeof(leaf)
records in the lump, where length is the size of the lump itself,
as specified in the lump directory.
leaf
If cluster is negative, the leaf is outside the map or otherwise
invalid.
Leaffaces
The leaffaces lump stores lists of face indices, with one list per leaf.
There are a total of length / sizeof(leafface) records in
the lump, where length is the size of the lump itself, as
specified in the lump directory.
leafface
Leafbrushes
The leafbrushes lump stores lists of brush indices, with one list per leaf.
There are a total of length / sizeof(leafbrush) records in
the lump, where length is the size of the lump itself, as
specified in the lump directory.
leafbrush
Models
The models lump describes rigid groups of world geometry. The first model
correponds to the base portion of the map while the remaining models
correspond to movable portions of the map, such as the map's doors,
platforms, and buttons. Each model has a list of faces and list of
brushes; these are especially important for the movable parts of the map,
which (unlike the base portion of the map) do not have BSP trees associated
with them. There are a total of length / sizeof(models)
records in the lump, where length is the size of the lump itself,
as specified in the lump directory.
model
Brushes
The brushes lump stores a set of brushes, which are in turn used for
collision detection. Each brush describes a convex volume as defined by
its surrounding surfaces. There are a total of length /
sizeof(brushes) records in the lump, where length is the
size of the lump itself, as specified in the lump directory.
brush
Brushsides
The brushsides lump stores descriptions of brush bounding surfaces. There
are a total of length / sizeof(brushsides) records in the
lump, where length is the size of the lump itself, as specified in
the lump directory.
brushside
Vertexes
The vertexes lump stores lists of vertices used to describe faces. There
are a total of length / sizeof(vertex) records in the lump,
where length is the size of the lump itself, as specified in the
lump directory.
vertex
Meshverts
The meshverts lump stores lists of vertex offsets, used to describe
generalized triangle meshes. There are a total of length /
sizeof(meshvert) records in the lump, where length is the
size of the lump itself, as specified in the lump directory.
meshvert
Effects
The effects lump stores references to volumetric shaders (typically fog)
which affect the rendering of a particular group of faces. There are a
total of length / sizeof(effect) records in the lump,
where length is the size of the lump itself, as specified in the
lump directory.
effect
Faces
The faces lump stores information used to render the surfaces of the map.
There are a total of length / sizeof(faces) records in the
lump, where length is the size of the lump itself, as specified in
the lump directory.
face
There are four types of faces: polygons, patches, meshes, and billboards.
Several components have different meanings depending on the face type.
For type 1 faces (polygons), vertex and n_vertexes
describe a set of vertices that form a polygon. The set always contains a
loop of vertices, and sometimes also includes an additional vertex near the
center of the polygon. For these faces, meshvert and
n_meshverts describe a valid polygon triangulation. Every three
meshverts describe a triangle. Each meshvert is an offset from the first
vertex of the face, given by vertex.
For type 2 faces (patches), vertex and n_vertexes
describe a 2D rectangular grid of control vertices with dimensions given by
size. Within this rectangular grid, regions of 3×3 vertices
represent biquadratic Bezier patches. Adjacent patches share a line of
three vertices. There are a total of
(size[0] - 1) / 2 by
(size[1] - 1) / 2 patches. Patches in the grid start at (i, j) given by:
For type 3 faces (meshes), meshvert and n_meshverts are
used to describe the independent triangles that form the mesh. As with
type 1 faces, every three meshverts describe a triangle, and each meshvert
is an offset from the first vertex of the face, given by vertex.
For type 4 faces (billboards), vertex describes the single vertex
that determines the location of the billboard. Billboards are used for
effects such as flares. Exactly how each billboard vertex is to be
interpreted has not been investigated.
The lm_ variables are primarily used to deal with lightmap data.
A face that has a lightmap has a non-negative lm_index. For such
a face, lm_index is the index of the image in the lightmaps lump
that contains the lighting data for the face. The data in the lightmap
image can be located using the rectangle specified by lm_start and
lm_size.
For type 1 faces (polygons) only, lm_origin and lm_vecs
can be used to compute the world-space positions corresponding to lightmap
samples. These positions can in turn be used to compute dynamic lighting
across the face.
None of the lm_ variables are used to compute texture coordinates
for indexing into lightmaps. In fact, lightmap coordinates need not be
computed. Instead, lightmap coordinates are simply stored with the
vertices used to describe each face.
Lightmaps
The lightmaps lump stores the light map textures used make surface lighting
look more realistic. There are a total of length /
sizeof(lightmap) records in the lump, where length is the
size of the lump itself, as specified in the lump directory.
lightmap
Lightvols
The lightvols lump stores a uniform grid of lighting information used to
illuminate non-map objects. There are a total of length /
sizeof(lightvol) records in the lump, where length is the
size of the lump itself, as specified in the lump directory.
Lightvols make up a 3D grid whose dimensions are:
lightvol
Visdata
The visdata lump stores bit vectors that provide cluster-to-cluster
visibility information. There is exactly one visdata record, with a
length equal to that specified in the lump directory.
visdata
Cluster x is visible from cluster y if the (1 << y % 8) bit of
vecs[x * sz_vecs + y / 8] is set.
string[64] name
Texture name.
int flags
Surface flags.
int contents
Content flags.
float[3] normal
Plane normal.
float dist
Distance from origin to plane along normal.
int plane
Plane index.
int[2] children
Children indices. Negative numbers are leaf indices: -(leaf+1).
int[3] mins
Integer bounding box min coord.
int[3] maxs
Integer bounding box max coord.
int cluster
Visdata cluster index.
int area
Areaportal area.
int[3] mins
Integer bounding box min coord.
int[3] maxs
Integer bounding box max coord.
int leafface
First leafface for leaf.
int n_leaffaces
Number of leaffaces for leaf.
int leafbrush
First leafbrush for leaf.
int n_leafbrushes
Number of leafbrushes for leaf.
int face
Face index.
int brush
Brush index.
float[3] mins
Bounding box min coord.
float[3] maxs
Bounding box max coord.
int face
First face for model.
int n_faces
Number of faces for model.
int brush
First brush for model.
int n_brushes
Number of brushes for model.
int brushside
First brushside for brush.
int n_brushsides
Number of brushsides for brush.
int texture
Texture index.
int plane
Plane index.
int texture
Texture index.
float[3] position
Vertex position.
float[2][2] texcoord
Vertex texture coordinates. 0=surface, 1=lightmap.
float[3] normal
Vertex normal.
ubyte[4] color
Vertex color. RGBA.
int offset
Vertex index offset, relative to first vertex of
corresponding face.
string[64] name
Effect shader.
int brush
Brush that generated this effect.
int unknown
Always 5, except in q3dm8, which has one effect with -1.
int texture
Texture index.
int effect
Index into lump 12 (Effects), or -1.
int type
Face type. 1=polygon, 2=patch, 3=mesh, 4=billboard
int vertex
Index of first vertex.
int n_vertexes
Number of vertices.
int meshvert
Index of first meshvert.
int n_meshverts
Number of meshverts.
int lm_index
Lightmap index.
int[2] lm_start
Corner of this face's lightmap image in lightmap.
int[2] lm_size
Size of this face's lightmap image in lightmap.
float[3] lm_origin
World space origin of lightmap.
float[2][3] lm_vecs
World space lightmap s and t unit vectors.
float[3] normal
Surface normal.
int[2] size
Patch dimensions.
i = 2n, n in [ 0 .. (size[0] - 1) / 2 ), and
j = 2m, m in [ 0 .. (size[1] - 1) / 2 ).
ubyte[128][128][3] map
Lightmap color data. RGB.
nx = floor(models[0].maxs[0] / 64) - ceil(models[0].mins[0] / 64) + 1
ny = floor(models[0].maxs[1] / 64) - ceil(models[0].mins[1] / 64) + 1
nz = floor(models[0].maxs[2] / 128) - ceil(models[0].mins[2] / 128) + 1
ubyte[3] ambient
Ambient color component. RGB.
ubyte[3] directional
Directional color component. RGB.
ubyte[2] dir
Direction to light. 0=phi, 1=theta.
int n_vecs
Number of vectors.
int sz_vecs
Size of each vector, in bytes.
ubyte[n_vecs * sz_vecs] vecs
Visibility data. One bit per cluster per vector.
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This document is very brief. I have gathered more information, but have not had time to write it up. Occasionally, I add more information to this document.
At some point I put together a page that describes triangle meshes and other q3 leaf elements. I forget the exact reason I created that page, but you might find it interesting.
Feel free to ask for clarification, but please accept my apologies if I can't find the time to answer.
Keywords: quake 3 quake3 q3 arena quake3arena q3arena map bsp file spec specs format