Editing ExtraData (section)

=Linedefs =

Linedefs define walls, two-sided textures, and provide action triggers within maps. 

Each field in the linedef definition, with the exception of the '''recordnum''' field, is optional. If a field is not provided, it takes on the default value indicated below the syntax information. Fields may also be provided in any order. 

Note that the order of linedef definitions in ExtraData is not important. The '''recordnum''' field serves to identify linedef records. 

==Creating ExtraData Linedefs ==

Linedef records in ExtraData are associated either with lines which bear the ExtraData Control Line Special (270), or with any linedef in a DOOM-format map which uses a parameterized line special. You can place the 270 special, as well as parameterized special numbers, into the normal "special" field of a line using virtually any map editor. Editors with Eternity-specific configurations should support these specials natively.

Each control linedef (or directly-used parameterized special) specifies its corresponding ExtraData linedef record number as an integer value in its linedef tag field. If your editor does not allow entering arbitrary values up to 32767 into the tag field of linedefs, you will need to use the BOOM command-line editor, CLED. As of the initial writing time of this document, both DETH and Doom Builder support entering arbitrary integer values for the tag field. Check your editor's documentation or user interface to verify if it supports this. 

The flags, sidedefs, textures, and location of the ExtraData control linedef are used normally by the line and cannot be altered from within ExtraData. The true special (if 270 is used) and tag fields of the linedef, along with any extended fields, are specified in the ExtraData record which the control linedef references. 

Any number of linedefs can reference the same ExtraData record. In the event that a control linedef references a non-existent ExtraData record or the ExtraData script for a level is missing, the special and tag of the ExtraData control linedef will both be set to zero. 

==Linedef Syntax and Fields ==

The syntax of the ExtraData linedef record is as follows. Remember that all fields except the '''recordnum''' field are optional and can be specified in any order. 
 linedef
 {
   recordnum <unique number>
   
   // These fields are normal linedef fields
   special <number> OR <special name>
   tag <number>
   
   // These fields are ExtraData extensions
   extflags <extended line flags list>
   args { <special field>, ... }
   id <number>
   alpha <number>
 }
===Explanation of fields: ===
====recordnum====
The recordnum serves to identify this record, and is the number which ExtraData control linedefs must use to associate themselves with a linedef record. Every ExtraData linedef record must have a unique record number. If a duplicate record number is detected, the engine will currently exit with an error message. The record number is limited to values between 0 and 32767 inclusive. Some editors may only allow input of numbers up to 255 in the linedef tag field. Beware of this. 

====special====
:''Default: 0 ''

The special field determines what [[Linedef_types|type of action]] may be taken when a line is crossed, used, shot, etc. There are three types of linedef specials in Eternity: normal, generalized, and parameterized. Parameterized specials use the '''args''' field documented below to provide complete customization of line actions. 

This field can accept numbers for any special type, including generalized and parameterized, but it can also accept special names for parameterized line types. See the [[Detailed parameterized linedef specification]] for a complete list of the available names.

====tag====
:''Default: 0 ''

The tag of the linedef, used by DOOM-style line specials and sector effects.

====extflags====
:''Default: No flags are set by default. ''

This field specifies extended linedef flag values which impact the functionality of parameterized linedef specials. This field uses the same syntax as BEX/EDF flag strings, but the syntax will be reviewed here for completeness. 

A BEX flag list is a string of flag names separated by whitespace, pipe characters, commas, or plus characters. In ExtraData, if a flag list contains whitespace, commas, or plus signs, it must be enclosed in double or single quotations. Flags are combined using bitwise-OR logic, so a flag name can be specified more than once. Specifying a flag name causes that flag to be turned on. The default state of all flags is off. 

These are the flag values which are available for this field: 
    Flag name   Meaning
    ---------------------------------------------------------------------------------------
    CROSS         Linedef can be activated by being crossed.
    USE           Linedef can be activated by being used.
    IMPACT        Linedef can be activated by being shot.
    PUSH          Linedef can be activated by being pushed.
    PLAYER        Linedef can be activated by players.
    MONSTER       Linedef can be activated by objects with SPACMONSTER flag.
    MISSILE       Linedef can be activated by objects with SPACMISSILE flag.
    POLYOBJECT    Linedef can be activated by polyobjects (only works with CROSS)
    REPEAT        Linedef action is repeatable.
    1SONLY        Linedef can only be activated from first side.
    ADDITIVE      Linedef's midtexture is drawn with additive blending.
    BLOCKALL      Linedef will block everything that can be clipped.
    ZONEBOUNDARY  Linedef will work as a reverb effect boundary. Not needed for one-sided lines.
    CLIPMIDTEX    Linedef middle texture will not "bleed" on floor and ceiling.
    LOWERPORTAL   Linedef copies floor portal from its backside to its lower visible edge
    UPPERPORTAL   Linedef copies ceiling portal from its backside to its upper visible edge
    ---------------------------------------------------------------------------------------
    
Notes: IMPACT is currently only implemented for bullet weapons.

LOWERPORTAL and UPPERPORTAL are used to enable portals on the front side's upper and/or lower edges of a linedef, if the sector in front of the linedef is tall enough compared to the back sector to expose them. It is the only way to enable such portals, which will copy the sector portal(s) from the backside, if any.

Example flags fields -- All of these are equivalent: 
    // This is the only syntax that does not require quotations.
    
    linedef { extflags CROSS|PLAYER|MISSILE|REPEAT }
    
    // All of these syntaxes must be quoted, because unquoted strings in 
    // ExtraData cannot contain spaces, commas, or plus signs.
    
    linedef { extflags "CROSS PLAYER MISSILE REPEAT" }
    linedef { extflags "CROSS | PLAYER | MISSILE | REPEAT" }
    linedef { extflags "CROSS+PLAYER+MISSILE+REPEAT" }
    linedef { extflags "CROSS + PLAYER + MISSILE + REPEAT" }
    linedef { extflags "CROSS,PLAYER,MISSILE,REPEAT" }
    linedef { extflags "CROSS, PLAYER, MISSILE, REPEAT" }

====args====
:''Default: All args values default to zero. ''

The args field is a list of up to five special values which can have a broad range of meanings. Any values not provided in the args list will default, and if more than five values are provided, only the first five will be used. Currently, all args values are interpreted as integers (a non-number string evaluates to zero). This may change in the future. The args list is used by parameterized linedef specials. 

Example args list: 
    linedef { args { 0, 1, 2, 3, 4 } }

====id====
:''Default: 0''
This field is equivalent to '''tag'''. It will only have effect if '''tag''' is not already set.

====alpha====
:''Default: Alpha defaults to 1.0.''

The alpha field takes a value from 0.0 to 1.0 to set the opacity at which this linedef's midtexture is drawn. When combined with the ADDITIVE extflag, this can be used for additive-blended translucency as well.