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Paths (GTA SA)

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The 64 nodes*.dat files in gta3.img (or any other archive) contain the vehicle and ped paths and related information for GTA SA. There is a file for every 750×750 unit square, starting at the south-west corner (-3000, -3000) in row-major order.

However, paths for planes and trains are not stored in the node-files. Nodes can only be influenced through SCM using the opcodes 01EB and 03DE. Trains use paths in the tracks(1-4).dat and there are also paths for several missions and concrete cars. These paths are carrecs.

Most cars and pedestrians use nodes if they are not linked to an SCM or carrec path in any way.

Purpose

It is believed that these files were generated by some sort of path compiler during development of the game, and represent the processing-friendly binary data structures otherwise generated at runtime by previous versions of the game from files like paths.ipl and related. These files are still present in SA, but unused.

Since the built-in path compiler has apparently been removed from the game code or at least made nonfunctional, custom tools and techniques are required to generate new paths for SA.

Node files are streamed by the game — only the active area and those surrounding it are loaded at a time. Thus, corrupt files only lead to a game crash when the player enters the specific area.

The separate nodes*.dat files in the data\paths\ directory are ignored by the game.

File Format

Each file starts with a header, followed by 7 distinct sections.

Paths are stored as double-linked (thus undirected) graphs in adjacency list representation. There can be connections between separate areas.

The following data types and structures are used within this article:

  • INT8/UINT8 - signed/unsigned 8 bit integer (1 byte)
  • INT16/UINT16 - signed/unsigned 16 bit integer (2 byte)
  • INT32/UINT32 - signed/unsigned 32 bit integer (4 byte)
  • FLOAT - single precision floating point number (4 byte)

Header

The header contains information about the content of the various sections in the file. It has a size of 20 bytes.

4b - UINT32 - number of nodes (section 1)
4b - UINT32 - number of vehicle nodes (section 1a)
4b - UINT32 - number of ped nodes (section 1b)
4b - UINT32 - number of navi nodes (section 2)
4b - UINT32 - number of links (section 3/5/6)

Note: Sections related to links (3/5/6) have the same number of entries. These entries belong together and can be treated as one record by editors.

Section 1 - Path Nodes

The first section contains the node data for the paths. They are grouped by type: the list of vehicle nodes (cars, boats, race tracks) is followed by the ped nodes. Each node entry has a size of 28 bytes.

4b - UINT32   - Mem Address, unused
4b - UINT32   - always zero, unused
6b - INT16[3] - Position (XYZ), see below
2b - INT16    - unknown, always 0x7FFE
2b - UINT16   - Link ID
2b - UINT16   - Area ID (same as in filename)
2b - UINT16   - Node ID (increments by 1)
1b - UINT8    - Path Width
1b - UINT8    - Node Type
4b - UINT32   - Flags
Mem Address
These might have been pointers to path segment structures inside R*'s path compiler. Apparently they are ignored by the game and can be set to zero.
Position
This is the position of the node in world coordinates. To convert the signed words to floating point values divide them by 8.
Link ID
Index into sections 3, 5 and 6; used to find adjacent nodes.
Area ID and Node ID
Informational data, probably only used by the path generator. Area ID is always the same as the number in the filename, and Node ID is used to identify the node.
Path Width
This is used to modify the width of a path. The default value is 0 (zero). To convert the signed word to a floating point value divide it by 8 (unconfirmed).
Node Type
Defines some kind of group for the nodes. For vehicle nodes a value of 1 is for cars, 2 is for boats and higher values are for race tracks and other mission applications. For ped nodes there seems to be a distinct ID per village/city/area.
Flags
The first 4 bits define the number of links to adjacent nodes. The other bits are used to characterize node behavior, for more information see the table below.


Path Node Flags

Node flag bits, from low to high:

0-3   - Link Count
4-5   - TrafficLevel

The LinkCount defines the number of enties incrementing from the LinkID. The TrafficLevel uses 4 steps: 0 = full 1 = high 2 = medium 3 = low

A    06    - Road-Blocks
B    07    - Boats
C    08    - Emergency Vehicles only
D    09    - zero/unused
E    10    - unknown, grove house entrance paths ?
F    11    - zero/unused
G    12    - Is not Highway
H    13    - Is Highway (ignored for PED-Nodes and never 11 or 00 for Cars!)
I    14    - zero
J    15    - zero
K-M  16-19 - spawn probability (0x00 to 0x0F)[1]
O    20    - RoadBlock?
P    21    - Parking
Q    22    - zero
R    23    - RoadBlock?

 24-31 - zero (unused)

The following statistics on flag usage, grouped by path type, might be useful for further research:

   | Peds           | Cars           | #
#  | 37650          | 30587          | --
A  | 0              | 391 (1.28%)    | 391
B  | 0              | 1596 (5.22%)   | 1596
C  | 6019 (15.99%)  | 7669 (25.08%)  | 13688
D  | 0              | 0              | 0
E  | 17 (0.05%)     | 0              | 17
F  | 0              | 0              | 0
G  | 0              | 27936 (91.33%) | 27936
H  | 0              | 2539 (8.3%)    | 2539
I  | 0              | 0              | 0
J  | 0              | 0              | 0
K  | 37646 (99.98%) | 30582 (99.98%) | 68228
L  | 36676 (97.41%) | 30141 (98.54%) | 66817
M  | 36676 (97.41%) | 30136 (98.52%) | 66812
N  | 36607 (97.22%) | 30046 (98.23%) | 66653
O  | 0              | 8 (0.03%)      | 8
P  | 0              | 215 (0.7%)     | 215
Q  | 0              | 0              | 0
R  | 0              | 16 (0.05%)     | 16

Section 2 - Navi Nodes

The second section contains additional nodes, referred to as navigational nodes (navi nodes) in this article. Each record has a size of 14 bytes.

Navi nodes are used to define additional information for vehicle path segments; they are not used by ped paths. They are usually positioned between two adjacent vehicle nodes on an interpolated curve.

There may be bugs if you don't connect navi nodes correctly. The order to connect them is to check first which of the 2 linked nodes is 'higher'. That means which one has the higher node ID or area ID. The direction of linking is allways from higher to lower node. So the target node of the navi nodes is allways the lower node. (Espacially on area boundaries!)

4b - INT16[2] - Position (XY), see below
2b - UINT16   - Area ID
2b - UINT16   - Node ID
2b - INT8[2]  - Direction (XY), see below
4b - UINT32   - Flags
Position
This is the position of the navi node in world coordinates. To convert the signed words to floating point values divide them by 8.
Area ID and Node ID
These identify the target node a navi node is attached to.
Direction
This is a normalized vector pointing towards above mentioned target node, thus defining the general direction of the path segment. The vector components are represented by signed bytes with values within the interval [-100, 100], which corresponds to floating point values [-1.0, 1.0].

Navi Node Flags

These are used to characterize path segment behavior, for more information see the table below.

 0- 7 - unknown
 8-10 - number of left lanes
11-13 - number of right lanes
   14 - traffic light direction behavior
   15 - zero/unused
16,17 - traffic light behavior
18-31 - zero/unused
  • Right (forward) and left (backward) lanes are relative to the direction vector.
  • Experience has shown that navi nodes with attachments across area borders don't work too well. A possible solution is to attach them to the last instead of the next node, reverse the direction and exchange the lane numbers (if different) and other direction dependent flags. However, this will never work if previous, navi and next node are located in different areas each. (*)
  • Traffic light behavior can be a value from 0 to 2, where 1 and 2 are related to North-South and West-East cycles for traffic light synchronization.
  • The traffic light direction behavior is 1 if the navi node has the same direction as the traffic light and 0 if the navi node points somewhere else.

( (*) Gots clear after knowing how Navis are linked exactly. So you may use this but it is not obligation.)

Section 3 - Links

These are links to adjacent nodes, 4 bytes per entry.

2b - UINT16 - Area ID
2b - UINT16 - Node ID

Section 4 - Filler

This section hold data of constant size and content; its purpose is unknown. These 768 bytes are filled with the repeating data pattern 0xFF,0xFF,0x00,0x00 (192x), but this can be filled with zeros as well.

Section 5 - Navi Links

These are links to adjacent navi nodes, 2 bytes per entry. For indices from ped nodes (in section 1b) these are zero (unused).

2b - UINT16 - lower 10 bit are the Navi Node ID, upper 6 bit the corresponding Area ID

Please note that this limits the number of Navi Nodes (i.e. vehicle path segments) to 1024 per area file and the number of files/areas to 64!

Section 6 - Link Lengths

These are the distances between linked nodes in full units, 1 byte per entry. They are essential for path finding algorithms.

1b - UINT8 - Length

Section 7 - unknown

Unknown length, unknown content. This section is filled mainly with zeros, but there are exceptions of bytes with very low values greater than zero. It is assumed that this section is actually unused and might just be garbage.

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