Nvidia makes modding ray tracing into classic games easier with RTX Remix, starting with Portal

Recent mods and official re-releases show that the latest ray tracing techniques can fundamentally change the look of decades-old PC games. Nvidia’s upcoming RTX Remix promises to help modders bring the technology to many more classics, beginning with a remastered version of Portal this fall.

On Tuesday, Nvidia unveiled RTX Remix, a platform to help modders add ray tracing features to DirectX 8 and DirectX 9 games. The feature will also allow users to improve the textures of older games and add Nvidia Reflex and DLSS 3 (or DLSS 2.0 for users of Ampere and Turing GPUs).

An RTX Remix mod will replace a game’s original API with a 64-bit Vulkan renderer. Modders can export their RTX Remix mods into files that drop into a game’s directory alongside the executable, and they shouldn’t conflict with those from Nexus Mods or other sites.

In DX8 or DX9 games that support fixed function graphics pipelines, RTX Remix uses a custom D3D9 runtime to intercept draw calls and reinterpret game assets to convert them into the Universal Scene Description (USD) framework. The converted assets are compatible with many standard game development apps like Adobe Substance 3D Painter, Autodesk Maya, 3ds Max, Blender, SideFX Houdini, and Unreal Engine, making them easier for modders to edit.

Properly supporting ray tracing requires a game’s materials and textures to carry certain qualities that titles from the DX8 era generally lack. Remix allows users to add features like physically-based rendering materials, normal maps, and increased geometric detail, so they react to light more realistically. Modders can also use RTX Remix’s AI features to increase texture resolutions by 4x.

Nvidia’s platform also lets modders add new lighting to old games or use a game’s original lights to add ray-traced shadows, ambient occlusion, reflections, and global illumination. Additionally, RTX Remix includes three new lighting features Nvidia unveiled this week.

The first, RTX Direct Illumination (RTXDI), can add millions of tiny dynamic lights for things like fireballs, LEDs, or billboards to a scene without significantly impacting performance. Another new feature — Reservoir Spatio Temporal Importance Resampling Global Illumination (ReSTIRGI) — uses multiple bounces to calculate per-pixel correct indirect lighting. Finally, Nvidia’s Real Time Denoisers (NRD) should reduce noise in ray-traced lighting with better performance than earlier denoisers.

To demonstrate RTX Remix, Valve revealed Portal RTX — a ray-traced remaster of its 2007 puzzle game. Portal RTX adds rebuilt textures, high-polygon character models, DLSS, and Nvidia Reflex. Its ray tracing features include RTXDI, ReSTIRGI, NRD, Volumetric ray-traced lighting, and ray-traced emissive particles.

Portal RTX releases in November as a free upgrade to those owning the original title. Nvidia also demonstrated RTX Remix’s effects on The Elder Scrolls III: Morrowind and Mount & Blade.