Linedef
Linedefs are what make up the 'shape' (for lack of a better word) of your map. Every linedef is between two vertices and contains one or two sidedefs (which contain texture data). There are two major purposes of linedefs. The first is to give your map a definitive boundary between the player and the void (any area of a map behind a one-sided linedef is considered void space), and the second is to trigger action specials.
Linedefs can be assigned any of the action specials and will trigger them when a specified action occurs. You may flag linedefs to have their special executed when the player walks over the line, when the player uses the line (switches) or when the player pushes the line (similar to Quake or Quake 2 switches). Monsters may also trigger specials by walking over the line, and finally a projectile impact or cross can also trigger a special if you so desire.
In ZScript linedefs are controlled by the Line struct.
Specification (Doom format)
| Bytes | Data type | Description |
|---|---|---|
| 0-1 | Unsigned short | Beginning vertex |
| 2-3 | Unsigned short | Ending vertex |
| 4-5 | Unsigned short | Flags |
| 6-7 | Unsigned short | Line type |
| 8-9 | Unsigned short | Sector tag |
| 10-11 | Unsigned short | Right sidedef - 0xFFFF means there is no sidedef |
| 12-13 | Unsigned short | Left sidedef - 0xFFFF means there is no sidedef |
Specification (Hexen format)
| Bytes | Data Type | Description |
|---|---|---|
| 0-1 | Unsigned short | Beginning vertex |
| 2-3 | Unsigned short | Ending vertex |
| 4-5 | Unsigned short | Flags |
| 6 | Unsigned byte | Action special |
| 7 | Unsigned byte | Action argument 1 |
| 8 | Unsigned byte | Action argument 2 |
| 9 | Unsigned byte | Action argument 3 |
| 10 | Unsigned byte | Action argument 4 |
| 11 | Unsigned byte | Action argument 5 |
| 12-13 | Unsigned short | Right sidedef - 0xFFFF means there is no sidedef |
| 14-15 | Unsigned short | Left sidedef - 0xFFFF means there is no sidedef |
Linedef flags
There are several conflicts in the flag list, depending on game. Map translators are used to define how values are associated to flags in a binary map. UDMF allows to solve these conflicts by not using a bitfield array but instead referring to each flag by name. UDMF also allows to define the remaining flags without having to use a function such as Line_SetIdentification, and several flags are only available in this map format.
| Flag | Bit | Hex | Description | Mode | UDMF name | Line_SetBlocking name |
|---|---|---|---|---|---|---|
| BLOCKING | 0 | 0x0001 | blocks players and monsters | Doom | blocking | BLOCKF_CREATURES |
| BLOCKMONSTERS | 1 | 0x0002 | blocks monsters | Doom | blockmonsters | BLOCKF_MONSTERS |
| TWOSIDED | 2 | 0x0004 | two sided | Doom | twosided | |
| DONTPEGTOP | 3 | 0x0008 | upper texture is unpegged | Doom | dontpegtop | |
| DONTPEGBOTTOM | 4 | 0x0010 | lower texture is unpegged | Doom | dontpegbottom | |
| SECRET | 5 | 0x0020 | secret (shows as one-sided on automap) | Doom | secret | |
| SOUNDBLOCK | 6 | 0x0040 | blocks sound | Doom | blocksound | BLOCKF_SOUND |
| DONTDRAW | 7 | 0x0080 | never shows on automap | Doom | dontdraw | |
| MAPPED | 8 | 0x0100 | always shows on automap | Doom | mapped | |
| RAILING | 9 | 0x0200 | line is a railing | Strife | jumpover | BLOCKF_RAILING |
| PASSUSE | 9 | 0x0200 | passes use action | Boom | passuse | |
| REPEAT_SPECIAL | 9 | 0x0200 | can be activated more than once | ZDoom | repeatspecial | |
| BLOCK_FLOATERS | 10 | 0x0400 | Line blocks floating monsters | Strife | blockfloating | BLOCKF_FLOATERS |
| 3DMIDTEX | 10 | 0x0400 | Actors can walk on mid texture. | Eternity | midtex3d | |
| SPAC_Use | 10-12 | 0x0400 | activated when used by player | ZDoom | playeruse | |
| SPAC_MCross | 10-12 | 0x0800 | activated when crossed by monster | ZDoom | monstercross | |
| SPAC_Impact | 10-12 | 0x0C00 | activated when hit by projectile | ZDoom | impact | |
| SPAC_Push | 10-12 | 0x1000 | activated when bumped by player | ZDoom | playerpush | |
| SPAC_PCross | 10-12 | 0x1400 | activated crossed by projectile | ZDoom | missilecross | |
| SPAC_UseThrough | 10-12 | 0x1800 | activated when used by player (with pass through) | ZDoom | blocking | |
| TRANSLUCENT | 12 | 0x1000 | line is 25% translucent (alpha of 0.75) | Strife | translucent | |
| 13 | 0x2000 | line is 75% translucent (alpha of 0.25) | Strife | transparent | ||
| MONSTERSCANACTIVATE | 13 | 0x2000 | line can be activated by players and monsters | ZDoom | monsteractivate | |
| BLOCK_PLAYERS | 14 | 0x4000 | blocks players | ZDoom | blockplayers | BLOCKF_PLAYERS |
| BLOCKEVERYTHING | 15 | 0x8000 | blocks everything (includes gunshots & missiles) | ZDoom | blockeverything | BLOCKF_EVERYTHING |
| SPAC_Cross | - | - | activated when crossed by player (default) | ZDoom | playercross | |
| SPAC_AnyCross | - | - | activated by anything crossing it | ZDoom | anycross | |
| SPAC_MUse | - | - | activated by monsters using it | ZDoom | monsteruse | |
| SPAC_MPush | - | - | activated by monsters bumping into it | ZDoom | monsterpush | |
| FIRSTSIDEONLY | - | - | Line can only be triggered from the front side. | ZDoom | firstsideonly | |
| ZONEBOUNDARY | - | - | Line is a boundary for sound reverb zones. | ZDoom | zoneboundary | |
| CLIP_MIDTEX | - | - | Line's mid textures are clipped to floor and ceiling (default in Strife). | Strife | clipmidtex | |
| WRAP_MIDTEX | - | - | Line's mid textures are wrapped. | ZDoom | wrapmidtex | |
| CHECKSWITCHRANGE | - | - | Switches can only be activated when vertically reachable. | ZDoom | checkswitchrange | |
| BLOCKPROJECTILE | - | - | Line blocks all projectiles | ZDoom | blockprojectiles | BLOCKF_PROJECTILES |
| BLOCKUSE | - | - | Line blocks all use actions | ZDoom | blockuse | BLOCKF_USE |
| BLOCKSIGHT | - | - | Line blocks line of sight for monsters | ZDoom | blocksight | BLOCKF_SIGHT |
| BLOCKHITSCAN | - | - | Line blocks hitscan attacks | ZDoom | blockhitscan | BLOCKF_HITSCAN |
| 3DMIDTEX_IMPASS | - | - | Causes the mid texture to behave like an impassible line (projectiles pass through it). Used in conjunction with midtex3d. | ZDoom | midtex3dimpassible | |
| BLOCKLANDMONSTERS | - | - | Line blocks ground-based monsters (Monsters without the FLOAT flag). | ZDoom | blocklandmonsters | BLOCKF_LANDMONSTERS |
UDMF properties
In addition to the above flags, the Universal Doom Map Format allows to set a number of properties on linedefs. Unless otherwise specified, default values for integers and float is 0, and false for booleans. They include:
| Name | Type | Description |
|---|---|---|
| alpha | float | Translucency of this line, default is 1.0. |
| arg0str | string | Alternate string-based version of arg0, used for named scripts. |
| arg0 | integer | First parameter. |
| arg1 | integer | Second parameter. |
| arg2 | integer | Third parameter. |
| arg3 | integer | Fourth parameter. |
| arg4 | integer | Fifth parameter. |
| comment | string | A comment. This is purely for map authors' convenience as it is ignored by the engine. |
| locknumber | integer | Line special is locked, see key types and LOCKDEFS. |
| renderstyle | string | Render style, can be "translucent" or "add", default is "translucent". |
| sidefront | integer | Front sidedef index. No default value: a linedef without a front sidedef invalidates the entire map. |
| sideback | integer | Back sidedef index. Default = -1 for "no back side". |
| special | integer | Action special for the line. |
| moreids | string | Additional line tags, specified as a space-separated list of numbers, e.g., "2 666 1003 4505". |