xoxor4d/gta4-rtx

What it does

This is a compatibility layer for running Grand Theft Auto IV: The Complete Edition (1.2.0.59) under NVIDIA RTX Remix. It is not a remaster: it intercepts the game's draw calls and translates its meshes, lights, and materials into Remix API instances so that path tracing, HDR, DLSS Ray Reconstruction, and replacement assets can be used.

Key pieces include rendering 99% of meshes through the RemixAPI to cut CPU overhead, translating all game lights (including the sun) into Remix lights with per-light overrides, cascaded anti-culling, dynamic wetness and puddles, vehicle headlights split into pairs, working emissive surfaces, rain droplets, and a custom Remix runtime fork with a modified FusionFix. In-game tweaks live behind an F4 ImGui menu, and a screenshot/freecam mode is included. It ships alongside a baseline Remix mod and an AutoPBR mod.

It targets players who want to experiment with path-traced GTA IV and modders building Remix replacement scenes.

Install and run

1. Install GTA IV: The Complete Edition 1.2.0.59 and get the latest release.
2. Follow the instructions bundled with that release; the installer/updater handles the runtime and a_gta4-rtx.asi placement.
3. Launch the game normally.
4. Press F4 for compatibility and debug settings.
5. If traversal stutters heavily, launch through _LaunchWithProcessorAffinity_4Cores_GTA4.bat (8+ core CPUs) or _LaunchWithProcessorAffinity_2Cores_GTA4.bat (fewer cores) so GTA IV and Remix get separate physical cores.

To remove it, delete d3d9.dll and a_gta4-rtx.asi, or run _toggle-gta4-rtx.bat to switch Remix off; reinstall official FusionFix if the custom fork was used. Performance, troubleshooting, and usage notes are in the wiki.

Build from source

Clone with submodules (git clone --recurse-submodules https://github.com/xoxor4d/gta4-rtx.git), optionally set a GTA4_ROOT environment variable pointing at the folder containing GTAIV.exe, run generate-buildfiles_vs22.bat, and compile. Without GTA4_ROOT, rename gta4-rtx.dll to a_gta4-rtx.asi and copy it next to GTAIV.exe, copy the contents of assets into the game folder, and install gta4-rtx-base-mod. The ReleaseTracy configuration bundles the Tracy profiler 0.13.x client for frame and API-level tracing; running the game as administrator also captures CPU sampling.

Constraints

• Only GTA IV: The Complete Edition 1.2.0.59 is supported; other versions are not covered.
• RTX Remix has inherent overhead from intercepting draw calls, so expect CPU-bound spots even with the RemixAPI optimization; the README frames remaining issues as largely fixed rather than absent.
• The project uses a custom Remix runtime and a custom FusionFix fork; mixing it with other FusionFix installs requires care, and no license is declared in the repository.
• Windows is required for both play and compilation (VS project generation, DirectX 9 layer).

HotRepo's take

The repository recorded 12 stars gained on the C++ daily list on 2026-11-05, placing 9th that day, with a total of 843 stars and 23 forks. That is a narrow, single-snapshot signal: enough to show an active niche audience around path-traced GTA IV, but not a basis for a trend claim. The scope is deliberately narrow — one game version, one rendering stack — so its value is concentrated for players already set up with RTX Remix rather than as a general graphics mod.