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2077-gps-mod/README.md
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# EdgeWeightGPS
Cyberpunk 2077 RED4ext plugin that improves player GPS routing by penalizing
short-segment churn in the native GPS solver. The current validated default
pushes the GPS toward smoother, higher-momentum driving corridors without
globally forcing every route onto highways.
## Current Status
Working prototype, validated in-game.
- Route scoring patch: enabled.
- Live tuning file: enabled.
- Current default fixed-edge penalty: `80.0`.
- Highway multiplier: neutral `1.0`; the earlier highway-speed/class
experiments are not part of the playable default.
The active package is a RED4ext plugin only:
```text
red4ext/plugins/EdgeWeightGPS/EdgeWeightGPS.dll
red4ext/plugins/EdgeWeightGPS/momentum_weights.bin
red4ext/plugins/EdgeWeightGPS/solver_weights.bin
```
## What It Patches
Reverse engineering found the player GPS route search loop around the native
solver relaxation cluster. The useful patch surface is not the script-facing
`RunGPSQuery`/`UpdateGPSQuery` helpers and not the generated traffic
`maxSpeed` fields. The playable hook patches the two ordinary adjacency
expansion sites feeding the native relax/update routine at `0x40ba58`.
The plugin adds a nonnegative fixed cost to ordinary edge expansion. In
practice, this makes many tiny street segments and repeated 90-degree
stair-steps less attractive, while still allowing local roads when they are the
right path.
## Validation Summary
The default `80.0` penalty was selected after live A/B testing:
- `0.0`: vanilla behavior; visibly stair-stepped in highlighted routes.
- `40.0`: partial improvement, but still missed useful smoother corridors.
- `80.0`: best observed result; selected smoother high-speed corridors and
passed drive testing.
- `160.0`: too high; caused bad hairpins/local access and one fallback-style
route.
Drive validation at `80.0`:
- The Dogtown route used a smoother highway corridor and drove cleanly at high
speed.
- Live minimap recalculation still worked after a deliberate detour.
- Claire/Westbrook route also drove cleanly; one blind hill/ramp surprise was
driver unfamiliarity, not a route failure.
See [docs/gps-momentum-field-tests.md](docs/gps-momentum-field-tests.md) for
the detailed test notes, screenshots, and log references.
## Build
Build in the Fedora toolbox:
```bash
toolbox run -c 2077 ./tools/build_red4ext_shim.sh
```
This writes:
```text
build/red4ext/EdgeWeightGPS-mingw64/EdgeWeightGPS.dll
```
## Install Locally
Only install while the game is cold.
```bash
toolbox run -c 2077 ./tools/install_red4ext_shim.sh
```
The install script builds the DLL, installs it into the Flatpak Steam Cyberpunk
2077 folder, and writes the validated defaults:
- `momentum_weights.bin = 80.0`
- `solver_weights.bin = 1.0`
Override the game directory with `CYBERPUNK2077_GAME_DIR` if needed.
## Package
Create a redistributable RED4ext zip:
```bash
toolbox run -c 2077 ./tools/package_red4ext_mod.sh
```
The package is written under `dist/` and contains the `red4ext/` folder layout
expected by the game.
## Live Tuning
`momentum_weights.bin` is a single little-endian float32 and is hot-reloaded
every 500 ms while the game is running.
Useful presets:
```bash
python3 tools/write_momentum_weights.py vanilla # 0.0
python3 tools/write_momentum_weights.py default # 80.0
python3 tools/write_momentum_weights.py overstrong # 160.0, known too high
```
`solver_weights.bin` is still present for older highway multiplier experiments,
but the playable default keeps it neutral:
```bash
python3 tools/write_solver_weights.py vanilla # 1.0
```
## Repository Notes
This repository also contains older experiments and reverse-engineering tools:
- REDmod/archive traffic resource patchers.
- Traffic lane and connection probability patchers.
- Static disassembly helpers.
- RED4ext logging probes.
Those tools are retained because they explain the route-finding system and
document failed approaches, but they are not part of the current playable
package. The important debriefs are:
- [docs/traffic-system-debrief.md](docs/traffic-system-debrief.md)
- [docs/red4ext-logging-shim.md](docs/red4ext-logging-shim.md)
- [docs/gps-routing-research.md](docs/gps-routing-research.md)