salt/2077-gps-mod

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salt e3c6087738 Research GPS lane connection weighting

2026-06-19 21:24:54 -05:00

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Cyberpunk 2077 Traffic/GPS System Debrief

This is based on the public NativeDB RTTI dump, WolvenKit exports from the local Steam install, and the generated all.traffic_persistent resource from the Phantom Liberty archive.

The High-Level Shape

Cyberpunk appears to split "navigation" into at least two major domains:

pedestrian/NPC navigation over navmesh resources
vehicle/GPS routing over generated traffic lane resources

The public script/native type dump exposes worldNavigationScriptInterface and AINavigationSystem methods for navmesh path queries, but those are character navigation tools. They are not the car GPS. The car GPS system type exists as gamegpsGPSSystem, but its public RTTI surface does not expose planner methods that a REDscript mod can override.

That means the practical mod surface is data, not algorithm replacement. The native gamegpsGPSSystem likely builds or queries a graph from traffic lane resources, then renders a GPS line from the selected lane path.

Relevant Game Types

The useful RTTI types are:

gamegpsGPSSystem
gamegpsSettings
worldTrafficPersistentResource
worldTrafficPersistentData
worldTrafficLanePersistent
worldTrafficLanePlayerGPSInfo
worldTrafficLanePersistentFlags

gamegpsSettings contains display/refresh settings:

lineEffectOnFoot
lineEffectVehicle
fixedPathOffset
fixedPortalMappinOffset
pathRefreshTimeInterval
lastPlayerNavmeshPositionRefreshTimeIntervalSecs
maxPathDisplayLength

Those affect GPS presentation and refresh behavior, not edge selection.

worldTrafficPersistentResource is the key resource type. Its root chunk has data: worldTrafficPersistentData, which has:

lanes: array<worldTrafficLanePersistent>
neighborGroups: array<array<Uint16>>

Each lane has the actual graph metadata:

outLanes
inLanes
outline
accumulatedLengths
crowdCreationInfo
maxSpeed
deadEndStart
length
width
area
flags
subGraphId
playerGPSInfo
neighborGroupIndex
nodeRefHash
laneNumber
seqNumber
isReversed
roadMaterials
polygon

playerGPSInfo contains:

subGraphId
stronglyConnectedComponentId

That strongly suggests the GPS planner has a precomputed connectivity graph and uses connected-component/subgraph metadata to reject impossible paths quickly.

Resource Location

In this install, the important resource is:

base\worlds\03_night_city\sectors\_generated\traffic\all.traffic_persistent

It exists in both the basegame Night City archive and the Phantom Liberty Night City archive. For a Phantom Liberty install, the EP1 archive version should win:

archive/pc/ep1/ep1_1_nightcity.archive

WolvenKit can extract, serialize, deserialize, and pack this resource on Linux through wolvenkit.cli 8.18.1.

Lane Flags

worldTrafficLanePersistentFlags:

FromRoadSpline = 1
Bidirectional = 2
PatrolRoute = 4
Pavement = 8
Road = 16
Intersection = 32
NeverDeadEnd = 64
TrafficDisabled = 128
CrossWalk = 256
GPSOnly = 512
ShowDebug = 1024
Blockade = 2048
Yield = 4096
NoAIDriving = 8192
Highway = 16384
NoAutodrive = 32768

The important flags for GPS weighting are Road, Intersection, GPSOnly, and Highway. The important flags to avoid touching are Pavement, CrossWalk, TrafficDisabled, and Blockade.

Observed Lane Distribution

The local EP1 all.traffic_persistent resource contains 33,952 lanes when extracted from the archive's raw compressed segment.

Observed maxSpeed distribution:

all lanes:
  1: 12852
  15: 12107
  10: 5859
  17: 3027
  14: 96
  8: 8
  9: 2
  4: 1

highway lanes:
  17: 2700
  15: 164
  1: 2

road lanes:
  15: 11943
  10: 671
  17: 327
  14: 96
  8: 4

pavement lanes:
  1: 12848
  10: 5188
  8: 4
  9: 2
  4: 1

The values are not real-world mph/kph. They are compact game-scale lane speeds. Because highways are already mostly 17 and normal roads are mostly 15, a large value like 90 would be reckless. The mod currently uses conservative defaults:

highway speed target: 25
road speed floor: 15

That changes 2,519 lanes:

2,429 highway boosts
90 road floor boosts

It leaves pavement/crosswalk/blocked/disabled lanes alone.

What The Mod Actually Does

The mod does not replace the pathfinding algorithm.

It edits the traffic graph's lane metadata so the native GPS planner has better cost inputs. If the planner factors maxSpeed into traversal cost in the usual way, then a segment with the same physical length but higher maxSpeed becomes cheaper. That nudges the native planner toward highways and high-capacity roads without having to hook the planner itself.

Conceptually:

old cost ~= lane.length / lane.maxSpeed
new cost ~= lane.length / patched_lane.maxSpeed

The actual game formula is native and not exposed in RTTI, so this is an inference. The inference is supported by the presence of maxSpeed, length, connectivity data, and GPS-specific lane graph metadata in the same resource.

Why Not Just Write A New A*?

A standalone A* is easy. Integrating it into Cyberpunk's GPS is the hard part.

The game already has:

traffic lane connectivity
lane polygons/outlines
player lane matching
destination lane matching
dynamic refresh
minimap/world map rendering
quest mappin target integration
portal/entrance handling
route line effects

The script-facing gamegpsGPSSystem type does not expose hooks for replacing that pipeline. A custom planner would still need a way to feed its result back into the GPS renderer and route-following systems. Without native RED4ext hooks, that is much riskier than patching the resource data the existing pipeline already consumes.

Packaging Flow

The working flow is:

Read the archive index and extract the exact compressed segment for resource hash 3419764573789342681.
Decompress that KARK segment with WolvenKit CLI's Oodle command.
Serialize the CR2W resource to JSON.
Patch lane maxSpeed values.
Deserialize the patched JSON back to CR2W.
Put the CR2W back under the original resource path.
Pack an archive.
Place the archive in archive/pc/mod.

Do not use plain cp77tools extract for this resource. In this install, WolvenKit CLI extracted a 9,984,106 byte CR2W, while the stock archive segment declares and decompresses to 10,673,648 bytes. A vanilla control archive built from the smaller extraction crashed during load. A vanilla control archive built from the raw segment reached the game and the GPS worked normally.

The generated archive currently contains exactly:

base\worlds\03_night_city\sectors\_generated\traffic\all.traffic_persistent

Risks And Unknowns

The first major finding from in-game testing is that maxSpeed is not a useful GPS weighting lever. Raising highway lanes as high as 120 did not change GPS routes in the test case, but it did make freeway traffic noticeably faster. That means maxSpeed should be treated as traffic simulation data, not GPS route cost data.

The actual lane adjacency is not populated in all.traffic_persistent; every lane's outLanes array serialized empty. The adjacency is in:

base\worlds\03_night_city\sectors\_generated\traffic\all.lane_connections

That resource is a worldTrafficPersistentLaneConnectionsResource with one row per lane. Each row has inLanes and outlanes. Each outgoing connection contains laneIndex, exitProbabilityCompressed, isSharpAngle, nextLaneEntryPosition, and thisLaneExitPosition.

There is still no explicit edge cost field. The current best data-only test is to patch exitProbabilityCompressed: strongly favor road/GPSOnly/highway connections that enter or remain on highways, and lower competing non-highway exits. A prepared experimental archive changes 145 outgoing connection probabilities across 136 lanes.

The Oodle library was not available inside the toolbox, so WolvenKit packed with its Kraken fallback. A vanilla full-resource control archive loaded in game and GPS worked normally, so the earlier crash was caused by bad extracted data rather than the Kraken-packed archive container.

The patch targets the EP1 traffic resource because Phantom Liberty is installed. On a non-PL install, the basegame archive resource would need to be patched instead.

Future Improvements

Better versions of this mod could:

build district-specific presets
patch all.lane_connections probabilities around ramps and highway exits
inspect GPSOnly connector lanes separately
compare route output with probability-only archives enabled
locate any native or baked edge-cost data not exposed in RTTI
generate a diff report of every changed lane with flags, length, speed, and graph component
ship multiple archives: conservative, strong, and experimental

The next practical step is in-game route testing between known bad waypoint pairs, especially cases where vanilla GPS exits highways too early or cuts through surface streets.

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