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What just happened? Modders have used Nvidia’s RTX Remix toolset to apply bleeding-edge path-traced lighting to DirectX 7 and 8 games, mostly hailing from the early 2000s – but rarely anything as recent as Grand Theft Auto IV. The latest mod continues a long-running tradition of fan-made fixes and improvements to Rockstar’s 2008 classic.

Modder xoxor4d recently unveiled his ongoing work on a new renderer for Grand Theft Auto IV that incorporates full ray tracing. The mod could potentially become far more advanced (and demanding) than the ray tracing features Rockstar added to GTA V.

The mod is notable because, as a DirectX 9 title, GTA IV does not support the fixed-function pipelines required for RTX Remix. To overcome this, xoxor4d reverse-engineered a custom DLL interceptor to translate critical data between the game and Nvidia’s modding toolkit.

Even in an early state, path tracing introduces fundamental differences from the original version, making the lighting more natural with more comprehensive shadow coverage. However, much work remains before the mod can fully implement ray tracing.

For example, an optional setting disables the virtual “fill lights” that normally provide most of GTA IV’s interior lighting, so the game can rely on ray tracing from real light sources. However, the change will make certain scenes appear overly dark until the proper lighting information is updated for each room throughout the game’s massive world. All of the textures also require similar updates.

Predictably, applying path tracing makes GTA IV exponentially more demanding. As the above video demonstrates, an RTX 5080 can only maintain around 40 frames per second in DLSS 4K performance mode.

The mod is currently only available on xoxor4d’s Patreon, but it will likely come to GitHub or Nexus Mods after exiting beta. In the meantime, users interested in revisiting the PC version of GTA IV should try the FusionFix mod, which resolves many of the notoriously troubled port’s problems and makes the graphics more closely resemble the original console versions.

Other classics that have received path tracing mods include Painkiller, Vampire: The Masquerade – Bloodlines, Doom, Unreal, Half-Life, Colin McRae Rally 3, Need for Speed: Underground, and many more. The modder behind the GTA IV conversion is also bringing Nvidia’s technology to Call of Duty 4, Portal 2, and Left 4 Dead 2.