View source for List of L4D Series Nav Mesh Attributes

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In {{l4ds}}, [[Navigation Meshes|Navigation Mesh]] (or '''nav mesh''' / '''nav''' for short) play very important roles for the infected AI, and thus there are plently of attributes possessing very unique behaviors, intending to be applied by the level designer. Some are also necessary for a map to work.

There are two types of nav attributes, and these are what they do...

== Spawn Attributes ('TERROR') ==
These attributes are visualised only with the<code>z_debug 1</code>command, where the unique color of an attribute fills the insides of the highlighted navigation areas. Colors of multiple Spawn Attributes do not mix, and one will always override the other.

{| class="wikitable"
! Attribute !! Description
|-
| style="text-align:center;"| <code>BATTLEFIELD</code> || style="padding:6px;"| Designated regions where a planned crescendo event will play out. All infected spawning, except Versus modes, will halt so long Survivors stay in it. Once a panic event starts, ALL infected bots spawns ''only'' at areas designated by<code style="color:#E5E5E5;">BATTLEFIELD</code>attributes, meaning infected spawning halts if Survivors manage to step out the regions.

&nbsp;Should be applied to large regions of nav areas in the map; capable of containing many Infected spawn-friendly areas within it, and a<code style="color:#E5E5E5;">BATTLESTATION</code>area. If the play area has a way for Survivors to escape ahead, or the playing field constantly changes (like Gauntlet events), then this should not be used.
|-
| style="text-align:center;"| <code>BATTLESTATION</code> || style="padding:6px;"| Indicates to Survivor Bots a strong defensive area for a panic event, usually next to supplies/weapons. Survivor bots may roam then reside in these nav areas before/during a panic event, giving it up when they think its unsafe (E.g. Too far from any human player). Intended only for nav areas already containing either a<code style="color:#E5E5E5;">BATTLEFIELD</code>or<code style="color:#E5E5E5;">FINALE</code> attribute.

&nbsp;In {{l4d2}}, this attribute's behavior is mostly disabled, but can be brought back with the<code style="color:#E5E5E5; background-color: #202020;">sb_allow_leading</code>/<code style="color:#E5E5E5; background-color: #202020;">allow_all_bot_survivor_team</code>commands.
|-
| style="text-align:center;"| <code>CHECKPOINT</code> || style="padding:6px;"| Designates the start/transition areas of the map. The round starts when a survivor leaves this area, and ends with ''all'' and ''only'' the survivors standing on this, with the saferoom door closed. {{note|Prohibits spawning of Player controlled Specials.}}
|-
| style="text-align:center;"| <code>EMPTY</code> || style="padding:6px;"| Prevents ''only'' wandering/resting Commons from being populated. Useful to prevent commons hogging the limit in places where they play no role, usually outside the survivors's playable areas. (e.g. building rooftops).
|-
| style="text-align:center;"| <code>FINALE</code> || style="padding:6px;"| Indicates a finale area. Otherwise characteristics are similar to<code style="color:#E5E5E5;">BATTLEFIELD</code>attribute. This should be used extensively across your finale's nav areas, and contain a<code style="color:#E5E5E5;">BATTLESTATION</code>attribute within it.
|-
| style="text-align:center;"| <code>LYINGDOWN</code><br>{{only|{{l4d2}}}} || style="padding:6px;"| Commons lie down and rest when not aroused by player.
|-
| style="text-align:center;"| <code>NOT_CLEARABLE</code> || style="padding:6px;"| Prevents a nav area from being marked "cleared" by Survivors, which would otherwise disallow non-player infecteds from spawning; A nav area is 'cleared' once survivors have seen it, and removed all of its spawned infected.

&nbsp;Usually found in outer-most areas survivors have attackable line-of-sight to, but can't really see (e.g. through fog).
|-
| style="text-align:center;"| <code>NO_MOBS</code> || style="padding:6px;"| Prevents Mobs and player Tanks from spawning, but also prevents Specials from spawning in<code style="color:#E5E5E5;">BATTLEFIELD</code>nav areas. Good for making Mobs spawn desirable or more interesting areas, or to keep Mobs away from known areas that cause unnatural spawning.

&nbsp;A clever example of<code style="color:#E5E5E5;">NO_MOBS</code>is in the<code style="color:#E5E5E5;">c10m2_drainage</code>map, Death Toll - Drainage.<code style="color:#E5E5E5;">NO_MOBS</code>is used in the long pipes, so that Mobs must spawn in the upper areas and run at you down the lengths of the pipe, rather than just around the corners.
|-
| style="text-align:center;"| <code>NOTHREAT</code><br>{{only|{{l4d2}}}} || style="padding:6px;"| Disallow<code style="color:#E5E5E5;">THREAT</code>attribute from doing anything, if it is applied on the same nav area.
|-
| style="text-align:center;"| <code>OBSCURED</code> || style="padding:6px;"| A very powerful nav attribute; Allows infected to spawn even when there is line-of-sight to a survivor. To be used in nav areas that are visually obscured, yet not considered so by the Director. For example, tree props. Survivor bots's line-of-sight to these nav areas are blocked to prevent omniscient behavior.
<br>The Director can still create effective Mobs without the<code style="color:#E5E5E5;">OBSCURED</code>attribute, but will usually be much further outside the survivors's [[PVS]] compared to without. {{note|Props that have collisions disabled are always unable to block line-of-sight.}}
|-
| style="text-align:center;"| <code>RESCUE_VEHICLE</code> || style="padding:6px;"| Blocks a nav area until the {{ent|info_director}} input "''FinaleEscapeVehicleReadyForSurvivors''" is fired, which then unblocks nav areas with this attribute.

&nbsp;In {{l4d2}}, the [[VScript]] method [[Left 4 Dead 2/Script Functions#CNavMesh|NavMesh.UnblockRescueVehicleNav()]] can also be used to unblock<code style="color:#E5E5E5;">RESCUE_VEHICLE</code>attributes.
|-
| style="text-align:center;"| <code>STOP_SCAN</code> || style="padding:6px;"| Infected bots won't navigate through this. If<code style="color:#E5E5E5;">STOP_SCAN</code>attribute occupies a path entrance, Infected will spawn beyond the entrance if all Survivors pass it.

{{warning|If all survivors stand on this, no infected will spawn!}}
|}
=== Automatic ===
Spawn Attributes automatically added by the game, usually unnecessary to be marked manually in any way.
{| class="wikitable"
|-
! Attribute !! Description
|-
| style="text-align:center;"| <code>DOOR</code> || style="padding:6px;"| Survivor bots will monitor this nav area for interactable doors, while Infected bots may consider path alternatives if the door is closed. Also blocks off the spreading of the<code style="color:#E5E5E5;">RESCUE_CLOSET</code>attribute. Automatically assigned by  {{ent|prop_door_rotating}} .

&nbsp;When the door is destroyed, the attribute renames itself to the <code style="color:#E5E5E5;">DESTROYED_DOOR</code> name.
|-
| style="text-align:center;"| <code>ESCAPE_ROUTE</code> || style="padding:6px;"| Basic guideline path of map from start to finish by linking spawns/checkpoints to the ending checkpoint/finale. This path helps the game/AI to make proper decisions based on routes and level progression.

&nbsp;This should be left untouched, and let a<code style="color:#E5E5E5; background-color: #202020;">nav_analyze</code>session handle this.
|-
| style="text-align:center;"| <code>PLAYER_START</code> || style="padding:6px;"| Functionally similar to <code style="color:#E5E5E5;">CHECKPOINT</code>, but does not reduce spitter's acid spreading or pauses spawning of mobs and specials. Automatically assigned by  {{ent|info_player_start}} . {{note|If used in the starting saferoom, all dead players from the previous chapter will spawn with 100% HP instead of 50%.}}
|-
| style="text-align:center;"| <code>RESCUE_CLOSET</code> || style="padding:6px;"| A Rescue closet room, spreading of attributes contained by<code style="color:#E5E5E5;">DOOR</code>attribute. Wanderers are not allowed in this. Automatically assigned during a<code style="color:#E5E5E5; background-color: #202020;">nav_analyze</code>session.
|-
| style="text-align:center;"| <code>THREAT</code> || style="padding:6px;"| Acts as spawn suggestions for AI Boss Infecteds (Tank & Witch). Only nav areas along the<code style="color:#E5E5E5;">ESCAPE_ROUTE</code>path are candidates for<code style="color:#E5E5E5;">THREAT</code>attribute. If its closest escape route path has already been reached by survivors,<code style="color:#E5E5E5;">THREAT</code>will be removed.

&nbsp;Requires<code style="color:#E5E5E5; background-color: #202020;">nav_analyze</code>to be automatically marked at random areas.
|}

== Base Attributes ==
Attribtes that are stored the same way {{css}}'s debut attributes are.

Unlike Spawn Attributes, these don't fill a nav area with colors. They instead may have their own identifable pattern/shape made with lines, and can appear simulatiously with each other's. When recently hovered over, their names are shown for a short period.

Attributes<code style="color:#E5E5E5;">MOB_ONLY</code>and<code style="color:#E5E5E5;">TANK_ONLY</code>fill nav areas with colors, but are both technically Base Attributes, as their colors overlap with other Spawn Attributes.

{| class="wikitable"
|-
! style="width: 15%;"| Attribute
! Description
! style="width: 30%;"| {{css}}'s Addendum
|-
| style="text-align:center;"| <code>PRECISE</code>
| style="padding:6px;"| Disables "obstacle avoidance" behavior, which bots then no longer keep a distance from nearby characters or world geometry / {{ent|prop_static}} entities. Can be visualized with<code style="color:#E5E5E5; background-color: #202020;">nb_debug PATH</code>active (green cuboids).

This attribute is for narrow areas close to said "obstacles", as bots then avoid unwise decisions like walking off and falling.
| style="padding:6px;"| Identical, but bots are forced to face this nav area when navigating towards it.
|-
|}

=== Automatic ===
Base attributes automatically added by the game, usually unnecessary to be marked manually in any way.
{| class="wikitable"
|-
! Attribute
! Description
! style="width: 17%;"| {{css}}'s Addendum
|-
| style="text-align:center; font-size:13px"| <code>BLOCKED_ZOMBIE</code>
| style="padding:6px;"| Similar to<code style="color:#E5E5E5;">STOP_SCAN</code>attribute, but ''all'' players (Survivors and Specials) and NPCs (Commons and Witches) who enter this nav area won't have their "[[Left 4 Dead 2/Script Functions#CBaseCombatCharacter|last known nav area]]" be updated. Cannot be manually applied; requires {{ent|func_nav_blocker}} entity with '''teamToBlock''' set to 3.
| style="padding:6px;"| <nowiki>-none-</nowiki>
|-
| style="text-align:center; font-size:12px"| <code>BLOCKED_SURVIVOR</code>
| style="padding:6px;"| Similar to<code style="color:#E5E5E5;">BLOCKED_ZOMBIE</code>attribute, but instead blocks Survivor bot navigations. Jockies on survivors avoid this. Cannot be manually applied; requires<code style="color:#E5E5E5;">PLAYERCLIP</code>attribute or {{ent|script_nav_blocker}} entity with '''teamToBlock''' set to 2.{{warning|Infecteds can sometimes spawn on this, and they will think they aren't in any nav areas!}}
| style="padding:6px;"| <nowiki>-none-</nowiki>
|-
| style="text-align:center;"| <code>BREAKABLEWALL</code><br>{{only|{{l4d2}}}}
| style="padding:6px;"| Infected bots dislike navigating through this, except Smokers. Assigned by {{ent|prop_wall_breakable}}  on map load.
| style="padding:6px;"| <nowiki>-none-</nowiki>
|-
| style="text-align:center;"| <code>DAMAGING</code>
| style="padding:6px;"| Bots dislike navigating through this, except Jockies on a survivor. Cannot be manually applied, only entities like {{ent|witch}} or {{ent|trigger_hurt}} are able to apply this to nav areas.
| style="padding:6px;"| <nowiki>-none-</nowiki>
|-
| style="text-align:center;"| <code>MOB_ONLY</code>
| style="padding:6px;"| Only Mobs will navigate through this. The flow also won't compute through nav areas using this attribute.
<br>This can't be set manually! Only settable by entities such as {{ent|func_breakable}} with<code>''All Infected''</code>for '''Breakable by''' property, or a {{ent|func_nav_attribute_region}} entity. {{warning|This attribute doesn't persist on round restarts!}}
| style="padding:6px;"| <nowiki>-none-</nowiki>
|-
<!-- STAIRS is accounted for in the Source SDK 2013 I think? But its not saved to the mesh and exists on map spawn, so... -->
| style="text-align:center;"| <code>NO_MERGE</code> || style="padding:6px;"| Disallows this nav areas from being merged with other areas. Only usable during nav mesh generation to not merge areas with<code style="color:#E5E5E5;">JUMP</code>attribute, or<code style="color:#E5E5E5;">OBSTACLE_TOP</code>attribute. Can be manually applied but won't be visible.
| style="padding:6px;"| No differences.
|-
| style="text-align:center;"| <code>OBSTRUCTED</code>
| style="padding:6px;"| Survivor bots dislike navigating this. Cannot be manually applied, only entities like {{ent|prop_physics}} or {{ent|func_nav_avoidance_obstacle}} are able to apply this to nav areas.
| style="padding:6px;"| <nowiki>-none-</nowiki>
|-
| style="text-align:center;"| <code>PLAYERCLIP</code><br>{{only|{{l4d2}}}}
| style="padding:6px;"| Applied when intersecting with a brush having the [[Player clip]] texture. Blocks flow but also sets<code>-9999</code>for its own's flow. Automatically adds<code style="color:#E5E5E5;">BLOCKED_SURVIVOR</code>attribute.
| style="padding:6px;"| <nowiki>-none-</nowiki>
|-
| style="text-align:center;"| <code>STAIRS</code>
| style="padding:6px;"| Treats oncoming areas as even ground, so bots also disregard jumping for high ground, but still jump over gaps. Also disallows Commons from climbing.
| style="padding:6px;"| Identical, but Commons don't exist in this game.
|-
| style="text-align:center;"| <code>TANK_ONLY</code>
| style="padding:6px;"| Only Tanks will navigate through this. The flow also won't compute through nav areas using this attribute.
<br>This can't be set manually! Only settable by entities such as {{ent|prop_dynamic}} with<code>''Tank only''</code>for '''Breakable by''' property, or a {{ent|script_nav_attribute_region}} entity. {{warning|This attribute doesn't persist on round restarts!}}
| style="padding:6px;"| <nowiki>-none-</nowiki>
|}

=== Obsolete ===
Defunct / Deprecated leftover attributes from {{css}}. These attributes either have no practical functionality, or is superseded by existing attributes. but still can be applied.
{| class="wikitable"
|-
! style="width: 15%;"| Attribute
! Description
! style="width: 30%;"| {{css}}'s Addendum
|-
| style="text-align:center;"| <code>AVOID</code>
| style="padding:6px;"| In {{l4d2}}, only Jockies avoid this. No effect in {{l4d}}.
| style="padding:6px;"| Makes all bots unprefer this mesh, sometimes outright avoiding it if its necessary before a jump.
|-
| style="text-align:center;"| <code>CLIFF</code>
| style="padding:6px;"| Scrapped leftover. Currently used by the nav generation system to indicate its being delicate on generating nav areas.
| style="padding:6px;"| Identical.
|-
| style="text-align:center;"| <code>CROUCH</code>
| style="padding:6px;"| In {{l4d2}}, Blocks all Specials from this nav area but Smokers, and also spawning of all Specials. No visible effect in {{l4d}}. Automatically added by a<code style="color:#E5E5E5; background-color: #202020;">nav_analyze</code>session. {{note|All types of bots already crouch automatically independent of nav areas.}}
| style="padding:6px;"| Makes bots crouch.
|-
| style="text-align:center;"| <code>DONT_HIDE</code>
| style="padding:6px;"| While in a<code style="color:#E5E5E5; background-color: #202020;">nav_analyze</code>session, hiding spot markers (green and purple lines) generation is skipped for this nav area. Not used by any bots. {{note|This can compress the nav file's size!}}
| style="padding:6px;"| Identical, but the hiding spot markers aren't unused.
|-
| style="text-align:center;"| <code>JUMP</code>
| style="padding:6px;"| Prevents anything from ever spawning on it. {{note|All bots already automatically jump / climb based on nav connections.}} {{warning|Running <code>nav_generate_incremental</code> will delete all of these areas.}}
| style="padding:6px;"| Force bots to jump when they enter this nav area.
|-
| style="text-align:center;"| <code>NO_HOSTAGES</code>
| style="padding:6px;"| No effect.
| style="padding:6px;"| When leading a hostage, they won't navigate through this.
|-
| style="text-align:center;"| <code>NO_JUMP</code>
| style="padding:6px;"| Draws a red diamond on the nav area.
| style="padding:6px;"| Prevents jump attempts.
|-
| style="text-align:center;"| <code>RUN</code>
| style="padding:6px;"| Center of marked nav area is given a pair of blue arrows.
| style="padding:6px;"| Maintain running speed and don't slow down.
|-
| style="text-align:center;"| <code>OBSTACLE_TOP</code>
| style="padding:6px;"| Automatically added when a nav area is created above a prop entity. {{note|Not related to {{ent|func_nav_avoidance_obstacle}} entity.}}
| style="padding:6px;"| Identical.
|-
| style="text-align:center;"| <code>STOP</code>
| style="padding:6px;"| Center of marked nav area is given a red octagon.
| style="padding:6px;"| Halt for half a second when entering this nav area.
|-
| style="text-align:center;"| <code>STAND</code>
| style="padding:6px;"| No effect.
| style="padding:6px;"| Skip considering crouches ''only'' while in hiding spots.
|-
| style="text-align:center;"| <code>TRANSIENT</code>
| style="padding:6px;"| Turns the nav area's outlines into dotted lines.
| style="padding:6px;"| For every 2 seconds, see if this nav area is now blocked by something if<code style="color:#E5E5E5; background-color: #202020;">nav_edit</code>isn't enabled.
|-
| style="text-align:center;"| <code>WALK</code>
| style="padding:6px;"| Center of marked nav area is given a singular green arrows.
| Bots hold down the<code style="color:#E5E5E5; background-color: #202020;">+walk</code>key on this, and are also not preferred to be navigated by bots.
|-
| style="text-align:center;"| <code>UNDERWATER</code>
| style="padding:6px;"| Nav area is given a blue square/rectangle, which resides near the outlines of the nav area. Added automatically when a nav area is created, and is touching the insides of water.
| style="padding:6px;"| Falling on this nav area from a high place will be safe.
|-
|}

== Bit Values ==
This area seems to have incorrect values. After running scripts it appears that 2048 is checkpoint and not 4096. Take the values with precaution
{{note|This section may be moved to a new page in the future. If it has been one week since October 15 2021 GMT+8, this note is no longer relevant.}}
{{L4D series navbits table}}
[[Category:Level Design]]
[[Category:Left 4 Dead]]
[[Category:Left 4 Dead 2]]