While the official RTGI (Ray Traced Global Illumination) shader by Pascal Gilcher (Marty McFly) typically requires a Patreon subscription

Unlike many community mods, Marty McFly’s RTGI shader was placed behind a subscription paywall on Patreon, typically requiring a $5/month "Beta tier" membership to access.

Is it free? This is the tricky part. Pascal Gilcher’s RTGI shader is freemium.

Summary

Optimization Tip: Disable the game's native Ambient Occlusion (AO) and Motion Blur to give the shader more "room" to work and prevent visual artifacts. The Best Free Alternatives

• Pros: Produces noticeably richer indirect lighting and softer ambient occlusion than basic unlit or simple ambient models; works well for small scenes and indoor lighting setups.
• Cons: Bloom/overbright artifacts in high-intensity lighting, noisy indirect lighting in complex scenes, and visible temporal flicker without sufficient denoising or temporal smoothing.

Here is everything you need to know about downloading and installing free RTGI shaders.

; it is provided as a benefit for supporters of the developer. Patreon Access

Warning: If you find a site claiming to offer the latest Patreon version for free, be extremely cautious. These are often vectors for malware.