LEV files contain a complete level geometry. They are in a quite complex text format.
They are also huge (generally > 600K), but this isn't a problem, as you really cannot edit them as a text file, because of the many dependencies between the geometry elements.

• Geometry Elements
• The Adjoin/Mirror/Walk mechanism
• A Quick Note on Texturing
• File Format
  • Magic, Version number and general level info
  • Texture Table
  • Geometry Description
    • Sectors
      • Sector Flags
    • Vertices
    • Walls
      • Wall Flags

The basic geometry elements of a DF level are :

VERTEX	a point in a 2 dimensions projection (X and Z)
WALLS	a line joining 2 vertices
SECTOR	a collection of walls generally closed, can contain "gaps" or other sectors

As the game works with a two dimensions projection, the third (Y) dimension is coded at the sector level by a floor altitude and a ceiling altitude.
Note that this implies that floors and ceilings of a sector are always FLAT.

Sectors can however be layered on top of one another to give a "full 3D" feeling.

Each sector is coded with its walls and vertices, and is completely self contained

The relation between sectors is done at the wall level by the adjoin/mirror/walk mechanism.

1--------2    Sector 1 has 5 vertices (0 to 4) marked 0 1 2 A B
|        |                 5 walls    including AB (wall 3)
|   S1   |
|        |    Sector 2 has 4 vertices (0 to 3) marked 0 1 B A
0---B====A                 4 walls    including BA (wall 2)
    | S2 |
    1----0

So, to come back to the adjoin/mirror/walk mechanism, if S1 and S2 must be connected, an adjoin/mirror relation must be established.

+----1---+
|        |
0        2
| 4    3 |
+---+====+
    1  2 3
    +--0-+

This is quite simple :

• the adjoin is the number of the connected sector
• the mirror is the number of the connection wall

So we would need to set:

in S1 : W3.adjoin = S2 and W3.mirror = 2
in S2 : W2.adjoin = S1 and W2.mirror = 3

If there is no adjoin/mirror relationship, the values for adjoin and mirror will be -1.
Walk values seem to have no effect at all in a level, but they are mostly set to the same value as adjoin.

When you have adjacent sectors:

TOP	is ABOVE the ceiling of the other SC
BOT	is BELOW the floor of the other SC
MID	is everywhere you can see through to the other SC

Of course, the MID texture is not shown when walls are adjoined, so that you can see through!
Note: WL flag 1, bit 1 forces it back in place. See Wall Flags

The DF engine applys the floor and ceiling textures as if you had taken a picture and layed it face down. This gives the effect of while in DF ,that the left and right sides of the texture have been exchanged..(flipped on the X axis). To view them correctly you would have to be under the floor looking up while facing south.

The LEV file is composed of 3 parts:

• Magic, Version number and general level info
• Texture Table
• Geometry Description

The following comments are accepted:
# comment
DATA # comment

Magic and version number

| LEV 2.1

This is trivial.

General Level Info

This part contains the following data (sample from secbase.lev):

| LEVELNAME SECBASE | PALETTE SECBASE.PAL | MUSIC AVENGE.GMD | PARALLAX 1024.0000 1024.0000

It seems that LEVELNAME isn't used at all by DF.
MUSIC is also unused, because musics are hardcoded in dark.exe.
(AVENGE.GMD doesn't even exist in DF, I think it is a Tie Fighter music !)

PALETTE determines the palette (PAL) used in the level, you may change it.

PARALLAX determines how much the "exterior" backgrounds scroll as you turn.
1024 1024 means as you turn around 360 degrees, you will see 1024 pixel columns of background sky.
Vertical PARALLAX is similar, although of course you can't pitch 360 degrees in DF.

As there is a lot of TX information in a level, a texture table is created to avoid storing TX names in full at each occurrence.

Coding sample :

| TEXTURES 85 # number of textures | TEXTURE: TEX00.BM # texture 0 | TEXTURE: TEX01.BM # texture 1 | ... | TEXTURE: TEX84.BM # texture 84

Afterwards, all the textures are referred to by their 0 based index in this texture table.

Note that changing TX names in the TX table may be an ultra fast way to relook a level !

• Sectors
  • Sector Flags
• Vertices
• Walls
  • Wall Flags

| NUMSECTORS numsectors

Then each sector is described, with its vertices and walls.
Please note that the wall data is on ONE line, but has been split here for visual convenience.

| SECTOR scnum | NAME sectorname | AMBIENT 20 | FLOOR TEXTURE 80 -0.38 -0.06 2 | FLOOR ALTITUDE 0.00 | CEILING TEXTURE 0 0.00 0.00 2 | CEILING ALTITUDE -12.00 | SECOND ALTITUDE 0.00 | FLAGS 0 0 0 | LAYER 1 | | VERTICES numvertices | X: 252.00 Z: 224.00 # a vx | ... | | WALLS numwalls | WALL LEFT: 0 RIGHT: 1 \ MID: 0 0.00 0.00 0 \ TOP: 1 0.00 0.00 0 \ BOT: 2 0.17 0.00 0 \ SIGN: -1 0.00 0.00 \ ADJOIN: 57 MIRROR: 0 WALK: 57 \ FLAGS: 0 0 0 \ LIGHT: 5 | ...

Hmmm... heavy information!
Click a section to take it apart, it's not too difficult.

| SECTOR scnum

This is the sector number, it is zero based.

| NAME sectorname

This is both a link to the .INF file and a useful reminder.

| AMBIENT 20

Ambient light level in this sector.
Note that this value is used in GROMAS to indicate an amount of red fog, not a light level.
This is a good demonstration of the use of the CMP files.

| FLOOR TEXTURE 80 -0.38 -0.06 2

The TX to apply to the floor of the SC as an index in the TX table.
The following two floats are the X and Z offsets by which the TX must be moved before being mapped.
The third (int) value is unused.
It seems that floor textures must be 64x64, or the game engine does strange things.

| FLOOR ALTITUDE 0.00

The altitude of the floor of this SC. Note that the Y axis goes "down", so higher altitudes have lower values.

| CEILING TEXTURE 0 0.00 0.00 2 | CEILING ALTITUDE -12.00

Same as floor.

| SECOND ALTITUDE 0.00

This is used to indicate a second "floor" altitude in a sector. For instance, a second altitude of 4 will make you "enter into the floor" 4 deep. It will in addition make the sector water like and generate a splashing sound. If you set a negative second altitude, you will be able to walk higher on the sector, provided you also enter the sector higher. This is the way platforms are created (the platform object is only a visual clue).

| FLAGS 0 0 0

Three flags, the second of which is never used in the 14 original levels.
Change various things in the sector. See Sector Flags.

| LAYER 1

The layer on which the SC is (positive, 0 or negative).
This value is used in the game to make different maps corresponding to zones of altitude.
Note that this is only a logical grouping, but is also used by the map in the game.

FLAG 1

Bit Value	Description	Comment
1	EXTERIOR - NO CEIL. (SKY)	Note: actual ceiling limit will be the ceiling altitude + 100
2	DOOR	instant door (set ceiling altitude to OPEN state)
4	SHOT REFLECTION / MAG.SEAL	walls, floor and ceiling reflect weapon shots
8	EXTERIOR ADJOIN	will adjoin adjacent skies.
16	ICE FLOOR (NO FRICTION)	Requires ice cleats to walk normally
32	SNOW FLOOR	no apparent effects
64	EXPLODING WALL/DOOR	instant exploding door (set ceiling altitude to OPEN state)
128	EXTERIOR - NO FLOOR (PIT)	Note: actual floor limit will be the floor altitude - 100
256	EXTERIOR FLOOR ADJOIN	will adjoin adjacent pits
512	CRUSHING SECTOR	vertically moving elevators will crush the player
1024	NO WALL DRAW / "HORIZON"	removes walls of a sector(sector must be sky and pit to work properly)
2048	LOW DAMAGE
4096	HIGH DAMAGE (both = GAS)	2048 + 4096 can be combined for GAS
8192	NO SMART OBJECT REACTION	Enemies cannot open door (see below)
16384	SMART OBJECT REACTION	Enemies can open door (see below)
32768	SUBSECTOR	no apparent effects
65536	SAFE SECTOR	unknown - do not use!
131072	RENDERED	unknown - do not use!
262144	PLAYER
524288	SECRET SECTOR	increments the %secret when entered

Note on skies and pits:
These bits (1 and 128) will cause the ceiling and floor texture (respectively) to be drawn as a "sky", that is, on a vertical plane at infinite distance and affected by PARALLAX values. They also displace physical collision by 100 units; for example, when the player falls into a pit he will "hit the bottom" at an altitude of 100 units below the floor altitude (fatal unless cheats are on).

basic
inv
basic_auto
morph_move1
morph_move2
morph_spin1
morph_spin2
move_wall
rotate_wall
door
door_mid
door_inv

FLAG 2

is unused.

FLAG 3

When "message: system lights" is sent (eg. in TALAY when you turn on the generator), the engine copies the value here to the Ambient of the sector.

| VERTICES numvertices

This is the number of vertices that this SC has.

| X: 252.00 Z: 224.00 # a vx

List of the VXs. X and Z are trivial.

| WALLS numwalls

This is the number of walls that this SC has.

| WALL LEFT: 0 RIGHT: 1

These are the origin and destination vertices for this wall.

\ MID: 0 0.00 0.00 0

The TX to apply to the middle of the WL as an index in the TX table.
The following two floats are the X and Y offsets by which the TX must be moved before being mapped (remember Y goes down).
The third (int) value is unused.

\ TOP: 1 0.00 0.00 0 \ BOT: 2 0.17 0.00 0

Same as MID

\ SIGN: -1 0.00 0.00

A sign is a second TX on the same WL, its main use is to place switches.
First is the TX to apply to a sign on the WL as an index in the TX table.
The following two floats are the X and Y offsets by which the TX must be moved before being mapped (remember Y goes down). Also note that this is relative to the texturing of the wall. So if you offset the WALL, you have to add this offset to that of the SIGN.

\ ADJOIN: 57 MIRROR: 0 WALK: 57

See The Adjoin/Mirror/Walk mechanism.

\ FLAGS: 0 0 0

Three flags.
Change various things in the wall. See Wall Flags.

\ LIGHT: 5

Relative modification of the luminosity on this specific WL. Negative values are allowed.

FLAG 1

Bit Value	Description	Comment
1	ADJOINING MID TX	the MID TX is NOT removed. Can use with texture transparency for partially see-through wall.
2	ILLUMINATED SIGN
4	FLIP TEXTURE HORIZONTALLY
8	ELEV CAN CHANGE WALL LIGHT	Use with elevator change_wall_light
16	WALL TX ANCHORED	Texture does not move vertically with elevator movement
32	WALL MORPHS WITH ELEV	Use with morph_move and morph_spin elevators
64	ELEV CAN SCROLL TOP TX	Use with elevator scroll_wall
128	ELEV CAN SCROLL MID TX	Use with elevator scroll_wall
256	ELEV CAN SCROLL BOT TX	Use with elevator scroll_wall
512	ELEV CAN SCROLL SIGN TX	Use with elevator scroll_wall
1024	HIDE ON MAP
2048	SHOW AS NORMAL ON MAP	i.e. light green
4096	SIGN ANCHORED	Sign tx will not move with elevator
8192	WALL DAMAGES PLAYER
16384	SHOW AS LEDGE ON MAP	i.e. dark green
32768	SHOW AS DOOR ON MAP	i.e. yellow

Note: Bits 2048, 16384 and 32768 will override default appearance of walls on the map. For example, 2048 is used to "hide" secret doors by causing them to appear green instead of yellow.

is unused.

FLAG 3

Bit Value	Description	Comment
1	CAN ALWAYS WALK	Player will climb any height (equivalent of LAPOGO or "no clipping" mode)
2	BLOCK PLAYER & ENEMY MOVEMENT	Applies to adjoined walls
4	BLOCK ENEMY MOVEMENT	Applies to adjoined walls
8	BLOCK WEAPONS	Applies to adjoined walls

Flag 3 applies to adjoined walls. They alter whether the player, enemies and weapons will collide with adjoined walls. Bits 2, 4 and 8 are often used to create "glass windows" that can be seen through but block movement.