NAV (file format)

← Nav Mesh

Not to be confused with AIN.

It has been suggested that this article or section be merged with Nav Mesh. (Discuss)

A NAV file is a map specific Navigation Mesh file that defines the walkable space in a level for bots in GoldSrc (CS:CZ) and Source games. They usually reside in <game folder>/maps and can be integrated into BSPs in some Source games.^[Clarify]

Todo: Document GoldSrc version. Format is identical - Counter-Strike: Condition Zero uses version 5.

Games

In Counter-Strike: Source and Counter-Strike: Global Offensive, the file is generated automatically when bots are played or being added into a map for the first time on a specific map that doesn't have one.

Nav Mesh file write is open source in Source SDK 2013: https://github.com/ValveSoftware/source-sdk-2013/blob/0d8dceea4310fde5706b3ce1c70609d72a38efdf/mp/src/game/server/nav_file.cpp#L1071

Nav Mesh generation is also open source in Source SDK 2013: https://github.com/ValveSoftware/source-sdk-2013/blob/0d8dceea4310fde5706b3ce1c70609d72a38efdf/sp/src/game/server/nav_generate.cpp#L3399

Left 4 Dead games have extra data per nav-area, as well as in after the nav place directory (null term string + short?), both of which have unknown format.

File format

Todo: The information listed on the NAV file structure is too vague.

Confirm:At least two versions of .nav files.

Todo: Add approach spot data.

Note:This is reverse engineered data.

unsigned int magicNumber; // Magic number to check if the file is a .nav file (little endian 0xFEEDFACE)
unsigned int version; // Version of the .nav file, for example GMod and TF2 has 16

if ( version >= 10 ) {
	unsigned int subVersion; // Sub version of the .nav file, for example GMod has 0, TF2 has 2. This is usedt
}

if ( version >= 4 ) {
	unsigned int saveBspSize; // Size of source bsp file to verify that the bsp hasn't changed
}

if ( version >= 14 ) {
	unsigned char isAnalyzed;
}

if ( version >= 5 ) {
	// Callouts. Places data. This is the "Mid", "Banana", etc stuff that is used in this nav mesh
	unsigned short count;

	for( int i = 0; i < count; ++i ) {
		unsigned short len; // length of the name
		char name[len]; // The name. Maximum len is 256
	}

	if ( version > 11 ) {
		unsigned char m_hasUnnamedAreas;
	}
}

{
	// PreLoadAreas( count )
	// This is by default is completely unused, it is left for mods to store custom data
	// Assuming that the data is per nav area
	//for( int i = 0; i < count; ++i ) {

	//}
}

unsigned int areaCount; // number of CNavAreas
area_t area[areaCount]; // Area Data

if ( version >= 6 ) {
	unsigned int ladderCount; // number of CNavLadders
	ladder_t ladders[ladderCount]; // Ladder Data
}

{
	// Load Custom Data
	// Again, by default this is unused
}

Area

A navigation area is a bounding square in which bots can move.

struct nav_area_t {
	unsigned int ID; // Identifier of the navigation area.
	union AttributeBitField {
		unsigned char; // In NAV versions ≤ 8
		unsigned short; // In NAV versions ≤ 12
		unsigned int; // In NAV Versions ≥ 13
	};
	float nwCorner[3]; // North-West corner vector.
	float seCorner[3]; // South-East corner vector.
	float NorthEastZ; // Z coordinate of North-East corner.
	float SouthWestZ; // Z coordinate of South-West corner.

	connectionData_t connectionData[4]; // Connection data in NESW (North, East, South, West) order.

	unsigned char hidingSpotCount; // Amount of hiding spots.
	hidingSpot_t hidingSpots[hidingSpotCount]; // Hiding spot data.

	/* Approach spots were removed in NAV version 15.
	unsigned char approachSpotCount; // Amount of approach spots
	approachSpot_t approachSpotData[approachSpotCount]; // Approach spot data.
	*/

	unsigned int encounterPathCount; // Amount of encounter paths.
	encounterPath_t encounterPaths[encounterPathCount]; // Encounter path data.
	unsigned short PlaceID; // ID of place.

	// Ladder data stored in order of vertical direction (up then down).
	struct ladderIDSequence_t {
		unsigned int ladderCount; // Amount of ladder Ids.
		unsigned int ladderIDs[ladderCount]; // Ladder IDs
	} ladderIDSequence[2];
	float EarliestOccupyTimes[2]; // Earliest occupy times for teams.
	float LightIntensity[4]; // Light Intensities for each corner.

	unsigned int areaBindCount; // Amount of area-binds stored.
	nav_area_bind_t areaBindSequence[areaBindCount]; // Sequence of area-binds stored.

	unsigned int InheritVisibilityFromAreaID; // Inherit visibility from area.
	void* customData; // Game-specific data.
}

Approach Spot

Todo: Describe variables.

struct approachSpot_t {
	uint approachHereId; 
	uint approachPrevId;
	byte approachType;
	uint approachNextId;
	byte approachHow;
}

Area-bind

Area-binds are a structure type used in nav areas to determine the visibility between the parent area and another navigation area, based on area ID.

struct nav_area_bind_t {
  unsigned int target_area_id; // Area ID of area.
  unsigned char AttributeBitField; // Attribute flag field that determines the visibility type.
};

Area-binds were added in NAV version 16.

Connection

struct connectionData_t {
	unsigned int count; // Amount of connections.
	unsigned int AreaIDs[count]; // List of area IDs that each connection points to.
};

Hiding Spot

Hiding spots are data structures used to determine points in a nav mesh that bots can hide at.

enum Attribute : unsigned char // Hiding Spot attribute values.
{
	IN_COVER = 0x01, // In a corner with good hard cover nearby
	GOOD_SNIPER_SPOT = 0x02, // Had at least one decent sniping corridor
	IDEAL_SNIPER_SPOT = 0x04, // Can see either very far, or a large area, or both
	EXPOSED	= 0x08 // Spot in the open, usually on a ledge or cliff
};

struct hidingSpot_t {
	unsigned int ID; // Identifier of hide spot. Added in NAV version 2.
	float position[3]; // Position of the hiding spot. Added in NAV version 1.
	unsigned char Attributes; // Attribute field. Added in NAV version 2. Defaults to IN_COVER for version 1
};

Game	Used For
Team Fortress 2	Determines where Spy bots can lurk for targets.
Counter-Strike: Source	Determines where bots can take cover and shoot at.
Counter-Strike: Global Offensive	Determines where bots can take cover and shoot at.

Encounter Path

Encounter paths are structures used to determine routes to take to get to certain areas.

struct encounterPath_t {
	unsigned int EntryAreaID; // ID of the Area entered from.
	unsigned byte EntryDirection; // Direction of entry.
	unsigned int DestAreaID; // ID of the Area destination.
	unsigned byte DestDirection; // Direction towards the destination area.

	unsigned char encounterSpotCount; // Amount of encounter spots.
	encounterSpot_t encounterSpots[encounterSpotCount]; // Encounter spots.
};

Warning:Encounter paths are only used in Counter-Strike: Source and Counter-Strike: Global Offensive.

Encounter Spot

Encounter Spots (better termed waypoints) are data structures used in encounter paths to determine the order of area IDs in a route.

struct encounterSpot_t {
	unsigned int AreaID; // The Area ID to go to.
	unsigned char ParametricDistance; // Parametric distance in bytes.
};

Warning:Encounter spots are only used in Counter-Strike: Source and Counter-Strike: Global Offensive.

Ladder

A navigation mesh ladder.

struct nav_ladder_t {
	unsigned int ID; // Identifier of the navigation ladder.
	float width; // extent of ladder

	float top[3]; // top endpoint of ladder
	float bottom[3]; // bottom endpoint of ladder
	float length; // ladder length

	unsigned int direction; // Direction of the ladder (NavDirType)

	unsigned char bDangling; // if version 6, dangling status

	unsigned int topForwardArea; // area ID
	unsigned int topLeftArea; // area ID
	unsigned int topRightArea; // area ID
	unsigned int topBehindArea; // area ID
	unsigned int bottomArea; // area ID
}

Custom Data

Some games store custom data in areas.

Custom Area Data

Subversion	Data	Label
2	unsigned int	Team Fortress 2 specific attributes.
1	char[14]	Counter-Strike: Global Offensive unknown data.

Versions Used By Games

Game	Version	Subversion
Team Fortress 2	16	2
Garry's Mod	16	0
Left 4 Dead 2	16	14
Left 4 Dead	15	13
Counter-Strike: Source	9	n/a
Counter-Strike: Condition Zero	5	n/a

See also

• Nav Mesh Editing

NAV processors

• Nav file parser in C++.
• libSourceNav — a NAV parser in Common Lisp.
• Base NAV file format in Kaitai Struct.
• Nav file parser in Go. (Outdated)