The gaming modding community celebrated the release of version 1.0.0 of an ambitious project that implements RTX Remix technology in Grand Theft Auto IV. Desenvolvido by the modder known as xoxor4d, the mod introduces full path tracing to the 2008 classic by Rockstar Games, radically transforming Liberty City’s lighting system. The package is now publicly available through GitHub and is designed to work exclusively with NVIDIA RTX series graphics cards, due to its dependence on specific hardware for ray tracing processing.
This new tool fixes a series of incompatibilities that existed between the game’s original graphics engine, based on DirectX 9, and NVIDIA’s modern RTX Remix platform. With the modification installed, players gain access to an advanced settings menu, which can be accessed by pressing the Alt + X keys during the game. The first tests and demonstrations reveal an impressive visual leap, with notable improvements in reflections, shadows and the way light sources interact with the environment, providing a level of realism previously unimaginable for the title.
Despite the graphical modernization, the project exposes the limitations inherent in the original GTA IV code, which was not designed to take advantage of multi-core processors efficiently. The addition of path tracing, a technique that consumes intensive processing resources, exacerbates this CPU bottleneck. Testes performed at 4K resolution show that even cutting-edge graphics cards, such as the RTX 5080, face difficulties maintaining a stable frame rate without the aid of optimization technologies, highlighting how demanding the new lighting is.
The mod offers a number of features to overcome performance challenges, allowing a wider range of systems to run the game with the new lighting. Entre the main optimization tools, the following stand out:
- DLSS 4 technology, which uses artificial intelligence to reconstruct the image from a lower resolution, can increase the frame rate from 35-45 fps to more playable levels in Performance mode.
- The Frame Generation feature, which generates intermediate frames autonomously, adding between 55 and 85 fps on compatible systems and can exceed 100 fps with additional optimizations.
- Initialization scripts (.bat) that divide the processor cores between the game and the mod, ensuring that each process has dedicated resources and minimizing the occurrence of crashes and sudden drops in performance.
New generation lighting in Liberty City
The main attraction of the mod is the complete implementation of path tracing, which recalculates all the lighting in the scene in real time, simulating the physical behavior of light. Isso means that nighttime city lights, car headlights, and daytime sunlight generate dynamic, physically correct shadows and reflections. Wet surfaces during rain in Liberty City gain unprecedented realism, reflecting the environment in a natural way, without the exaggerated mirrored effect seen in older ray tracing implementations.
To achieve this result, the developer made fine adjustments to several aspects of the renderer. Foi necessary to correct “alpha blending”, a technique used to render transparent objects such as glass and fences, so that they interact correctly with the new lighting. Além In addition, emissive lights, such as those from signs and traffic lights, were optimized to render through a simpler function, guaranteeing a gain in performance without sacrificing visual quality. The accessible in-game menu allows users to choose between different graphical presets, balancing quality and performance, while dynamic shadows cast by buildings and vehicles transform city exploration.
The performance challenge on modern hardware
GTA IV’s graphical modernization comes at a significant performance cost. Benchmarks made with an Intel Core i7-14700F processor, 32 GB of DDR4 memory and an RTX 5080 graphics card demonstrate the current limits of the technology. When running the game at native 4K resolution, without the aid of upscaling, the average frame rate often falls below 60 fps, a level considered ideal for fluid gameplay.
The bottleneck isn’t just in the video card. GTA IV’s RAGE engine is notoriously “CPU bound”, that is, limited by the processor’s performance, especially in scenes with many pedestrians and intense traffic. The RTX Remix adds its own processing load, which competes for resources with the game, exacerbating the problem in dense areas like Algonquin’s avenues.
To mitigate these issues, the mod includes a customized version of FusionFix, a popular community fix that resolves several bugs from the original game. The standard version of FusionFix proved to be unstable with the RTX Remix, leading the developer to create an adapted “fork” that guarantees greater compatibility and stability when running with path tracing.
Technologies to optimize gameplay
Fortunately, the mod integrates the latest NVIDIA technologies to make the experience viable. DLSS Frame Generation is crucial as it can multiply the frame rate by creating and inserting AI-generated frames between traditionally rendered frames. Essa technique is mainly responsible for taking performance to comfortable levels at high resolutions.
Along with Frame Generation, DLSS Super Resolution (upscaling) plays a vital role. When selecting “Performance” mode, the game is rendered internally at a lower resolution (such as 1080p) and then rebuilt to 4K with the help of artificial intelligence, relieving the load on the GPU and resulting in a large FPS jump.
Processor affinity scripts are another smart solution. The “LaunchWithProcessorAffinity_2Cores_GTA4.bat” file forces the game’s executable to use only two CPU cores, leaving the others free for the RTX Remix process. Outra option, “Half_GTA4__Half_Remix.bat”, divides the cores in a balanced way, making it ideal for processors with a large number of cores.
To ensure correct operation, the developer recommends removing any custom launch arguments in the game properties in Steam, as they may conflict with the mod’s scripts. Thin Ajustes, such as the “Tree Alpha Cutout” configuration, are also available to optimize performance in heavily vegetated areas.
Installation and compatibility guide
The installation process has been simplified to make it easier for the community to access. Users just need to extract the contents of the downloaded file directly to the root folder where the “GTAIV.exe” executable is located. The package already includes the installer for the adapted version of FusionFix, which is essential for the game’s stability with the mod activated.
The modification is officially compatible with the latest version of the game, “The Complete Edition 1.2.0.59”. In some cases, an additional step may be required: renaming the “gta4-rtx.dll” file to “a_gta4-rtx.asi” if the system does not have a specific environment variable configured, ensuring that the mod loads correctly when starting the game.
The future of the project and the role of the community
The release of version 1.0.0 marks the end of the early access period, which was exclusive to backers on Patreon, and lays a solid foundation for the future. The RTX Remix platform is not limited to lighting; it opens the door for the modding community to completely replace the game’s visual assets, such as textures and 3D models. Isso means that future updates could bring textures with PBR (Physically Based Rendering) materials, high-polygon count vehicle and character models, and even improved vegetation. The developer has already signaled plans to explore virtual reality (VR) support and new camera options, while the community can use the tool to create complete remasters of assets, exporting them to modern engines like Unreal Engine or Blender for reworking. Community feedback, collected primarily via Discord, will be critical in guiding the project’s next steps and refinements.
Technical details of the mod implementation
The development of this mod represents a feat of reverse engineering. Para before the RTX Remix could work, xoxor4d needed to dissect the original GTA IV renderer code to understand how it processed graphics. The mod acts as a bridge, intercepting the DirectX 9 draw calls that the game sends to the graphics card. Esses data, previously opaque and specific to the game engine, is translated into a format that the Remix platform can interpret. From there, Remix takes control, discarding the original lighting and reconstructing the scene with path tracing. Esse process was particularly complex for elements such as the weather system, fog, and post-processing effects, which required the creation of a custom runtime for the data to be converted correctly. The performance overhead arises mainly from the need to intercept and process each detailed object mesh, which, in addition to the CPU bottlenecks of the base game, explains the high hardware requirement.
