RTX Remix is a revolutionary modding platform to remaster classic DirectX 8 and 9 games with path tracing, NVIDIA DLSS, AI-enhanced textures, and user-created assets. RTX Remix, part of the NVIDIA Studio suite of apps, is composed of two core components that work together to enable modders to remaster classic PC games: the RTX Remix creator toolkit, and a custom RTX Remix runtime.

The RTX Remix creator toolkit, built on NVIDIA Omniverse and used to develop Portal with RTX, allows modders to assign new assets and lights within their remastered scene, and use AI tools to rebuild the look of any asset. The RTX Remix creator toolkit Early Access is coming soon. The RTX Remix runtime captures a game scene, and replaces assets at playback while injecting RTX technology, such as path tracing, DLSS 3 and Reflex into the game. Already, mod developers have been using the RTX Remix runtime from Portal With RTX to create experimental ray traced scenes in numerous classic games. To further empower the mod development community to extend Remix's game compatibility and feature set, NVIDIA is releasing the RTX Remix runtime as open source on GitHub today.The RTX Remix runtime is open source with a permissive MIT license, and includes the following components:

• USD capture and replacement modules, which are responsible for capturing a game scene to USD, and replacing original game assets with modded game assets at runtime.
• Bridge, which translates the renderer from a x86 to a x64 instruction set. This component uncaps the memory available for rendering.
• Scene manager, which uses information coming through the D3D9 fixed function API to create a representation of the original scene, track game objects frame to frame, and set up the scene to be path traced.
• The core path tracer, which includes the rendering loop, the material handling, and the game specific rendering features (e.g., decals and particles). Please note, the various technologies (DLSS, NRD, RTXDI) that accelerate our path tracer and enable it to render in real time will continue to be available via their existing SDKs and licenses from the NVIDIA Developer portal.

Open sourcing unlocks numerous possibilities to extend the feature set of the Remix runtime. A few examples of projects that advanced mod developers might tackle via source code access include:

• Making more of their favorite games compatible with Remix
• Modernizing the fluid simulation to render smoke and fire with realistic volumetrics
• Injecting custom post effects shaders in the runtime
• Adding animated lights (e.g., flickering fire, or lights that cycle through colors)
• Replacing animated character meshes
• Changing camera positions in games (e.g., turning a first person game into an isometric one)
• Incorporating virtual reality support into the renderer
• Implementing dynamic conditional replacements (e.g., add fog or change a light in response to a player's position)
• There is ample opportunity to change how classic titles are played, and open source widens the possibilities beyond our imagination. We look forward to seeing what mod developers will build with source access.

For PC gamers, an open source RTX Remix runtime will help broaden the variety of games with RTX mods and the types of mods themselves.

How To Get Involved
The RTX Remix runtime source code can be found on GitHub.

Our main goal is to expand game compatibility and extend the features of Remix in collaboration with the community. In keeping with that aim, NVIDIA will accept pull requests on Github for code submissions from the community, provide feedback, and help advance code until it is mature enough to be merged into the official RTX Remix runtime.

To further help the community with Remix, several Remix engineers have joined the community-led RTX Remix Showcase Discord server, are providing guidelines on compatibility, and responding to mod developers' questions about RTX Remix. If you are looking to get started with your own Remix runtime open source project, head over to the Discord to find subject matter experts to collaborate with. We have also prepared some starter guides and documentation for mod developers as we continue to prepare the RTX Remix application.

Modding is all about community, and providing an open source RTX Remix runtime will help empower mod developers to expand Remix compatibility to even more classic PC games. We look forward to seeing how creators usher in this new era of modding with RTX Remix.