Tracing Shader Rtgi 0.33 — Reshade Ray

I’ve written this for a typical PC gaming/graphics enthusiast blog — informative, slightly technical, but not overly academic.

Survey: Reshade Ray Tracing shader — RTGI 0.33

Summary

RTGI 0.33 is a screen-space/global-illumination-like shader for ReShade that simulates ray-traced indirect lighting and ambient occlusion using a combination of screen-space ray marching, temporal accumulation, and heuristic denoising. It’s intended to deliver convincing soft indirect light and contact shadows without hardware ray-tracing.

What it does well

Indirect lighting: Produces plausible bounced light and color bleeding from nearby surfaces, improving scene depth and material separation.
Contact shadows / AO: Adds crisp contact shadows in creases and around small geometry that standard SSAO often misses.
Temporal stability: Uses frame-to-frame accumulation and a reprojection scheme to smooth noise while preserving detail in slowly moving scenes.
Performance-control knobs: Multiple quality presets and parameters (ray length, sample count, denoise strength, temporal weight) let users trade quality for framerate.
Compatibility: Works in many DX9/DX11/DX12 games that expose required depth/normals; integrates into existing ReShade pipelines.

Key limitations and trade-offs

Screen-space constraints: Cannot see off-screen or behind occluders — indirect lighting is limited to what’s visible in the current frame, so results can flicker or be incorrect near occluded light sources.
Ghosting / temporal lag: Temporal accumulation can produce ghosting or smeared lighting on fast camera motions or dynamic geometry; higher temporal responsiveness reduces noise but increases flicker.
Noise at lower settings: At moderate performance settings, ray marching produces noticeable noise that relies on temporal accumulation to hide; in rapid motion this noise becomes visible.
Material/BRDF simplifications: RTGI uses simplified lighting heuristics rather than full physical BRDF integration; metallicness/gloss differences are approximated, so results may not match true path-traced renders.
Depth/normal artifacts: Requires clean depth and normal buffers — HUD elements, particles, or games that present inconsistent buffers can produce artifacts.
VR/unusual frame rates: Temporal methods and reprojection can perform poorly in VR or variable frame-rate scenarios.

Technical approach (concise)

Screen-space ray marching: Casts rays from shaded pixel along hemisphere/direction(s), sampling scene depth to find occluders and accumulate light contribution.
Importance heuristics: Prioritizes short rays and uses biasing (cone/hemisphere sampling) to approximate diffuse energy distribution.
Temporal accumulation: Reprojects previous-frame results using motion vectors or depth-based reprojection to reduce variance.
Spatial denoising: Bilateral/edge-aware filters and multi-scale blurs retain edges while smoothing noise.
Energy compensation: User-adjustable intensity, radius, and color bleeding controls to tune output and avoid overbrightening.

Practical tuning tips

Start with a medium preset and increase ray length only if you need broader bounce light—long rays cost a lot.
Raise sample count if your camera is mostly static; reduce temporal accumulation when you notice ghosting on motion.
Use edge/normal thresholds to protect sharp silhouettes from denoising bleed.
If HUD or particle artifacts appear, enable mask options or exclude those elements from the shader’s inputs (game/config permitting).
Combine with a screen-space reflections/fill-light pass judiciously; stacking many heavy effects can blow performance.

Performance guidance

Cost drivers: ray count, maximum ray length, number of rays per pixel, temporal accumulation history size, denoiser passes.
GPU scaling: Run a quick profiling pass—lower ray count first, then shorten ray length; enable lower-resolution rendering (half-res) if supported.
Useful presets: Play with half-resolution + stronger denoising for 30–60% speed gain with moderate visual loss.

Comparison notes (vs. hardware RT / path tracing)

Visual: RTGI achieves a good cinematic look for many scenes but lacks physically accurate long-range GI, caustics, and correct multi-bounce energy distribution that true path tracing/hardware RT provide.
Performance: Far less expensive than hardware ray tracing for similar-looking diffuse GI in many scenes, but still costly compared to simple SSAO.
Use case: Best for modders or players wanting a perceptible visual uplift without requiring RT-capable GPUs.

Common issues and fixes

Flickering/ghosting on motion: lower temporal weight, increase reprojection robustness, or reduce history length.
Speckle/noise in dynamic scenes: increase sample count or denoiser strength, or lower temporal reliance.
Over-brightening: reduce intensity/gain and clamp indirect contribution.
Artifacts on screen edges: enable border handling or reduce ray length near screen bounds.
Incorrect colors/bleeding: check normals/depth quality and tweak color bleeding/occlusion bias.

When to use RTGI 0.33

When you want markedly better ambient and contact lighting in games that lack true ray tracing.
When you can accept some screen-space limitations and are willing to tune settings per game for best results.
Not recommended when absolute physical accuracy, VR stability, or perfect multi-bounce GI is required.

Conclusion RTGI 0.33 is a powerful ReShade shader offering a practical balance between visual improvement and performance cost. It’s most effective in static or slowly changing scenes where temporal accumulation can remove noise, and when properly tuned to the target hardware and game. Expect screen-space artifacts and simplified lighting behavior compared with true hardware ray tracing, but significant aesthetic gains for many titles.

If you want, I can:

produce a short tuning checklist tailored to a specific game or GPU, or
write an example recommended settings table for low/medium/high quality.

Ray Traced Global Illumination (RTGI) shader, developed by Pascal Gilcher (Marty McFly), is a sophisticated post-processing effect for ReShade that simulates real-time global illumination and ambient occlusion in almost any game. Unlike native ray tracing, it operates in screen space by tracing rays against the game's depth buffer, making it compatible with non-RTX GPUs. Key Features of RTGI 0.33

Released around August 2022, version 0.33 introduced several significant technical improvements: Motion Vectors Integration

: This was the standout feature for 0.33, allowing the shader to track movement between frames. This drastically improves temporal stability, reducing the flickering and "ghosting" artifacts common in earlier screen-space solutions. Enhanced Denoising

: Utilizing motion data enables more effective denoising, resulting in smoother lighting transitions and cleaner shadows. Hardware Independence

: It continues to work across a wide range of hardware, though it is demanding on performance due to the complexity of the calculations. Visual and Performance Impact Realistic Lighting

: RTGI physically simulates light bounces, adding depth to scenes that otherwise look "flat". It adds subtle glow beneath light sources (like portals in ) and accurate shadows at material edges. Performance Cost

: While more efficient than early versions (which could drop FPS from 60 to 15), RTGI is still resource-intensive and can significantly impact frame rates depending on the game and settings. Depth Buffer Requirement Reshade Ray Tracing shader RTGI 0.33

: The shader requires a properly configured depth buffer to work. Users must often manually adjust settings like RESHADE_DEPTH_INPUT_IS_INVERTED RESHADE_DEPTH_INPUT_IS_LOGARITHMIC to ensure the shader "sees" the game world correctly. How to Access and Install The RTGI shader is distributed through the Marty's Mods Patreon

, typically requiring a "Breakfast" tier membership ($5) or higher for beta access. Portal Reshade RTGI - The Working Class' RTX Portal

This essay explores the technical achievement and visual impact of the ReShade RTGI (Ray Traced Global Illumination) shader, specifically focusing on the advancements seen in version 0.33. The Evolution of Post-Process Lighting: ReShade RTGI 0.33

For decades, real-time lighting in video games relied on "pre-baked" maps and simplified screen-space effects that often failed to capture the nuances of light bounce and color bleeding. The introduction of the ReShade RTGI shader by Pascal Gilcher (Marty Stratton) fundamentally changed the landscape for enthusiast "modders," bringing sophisticated ray-tracing techniques to games that never natively supported them. Version 0.33 represents a significant milestone in this journey, refining the balance between visual fidelity and hardware performance. The Technical Foundation

At its core, RTGI (Ray Traced Global Illumination) works by utilizing the "depth buffer" of a game to simulate how light rays interact with the visible environment. Unlike traditional Screen Space Ambient Occlusion (SSAO), which merely adds contact shadows, RTGI calculates how light bounces off surfaces. This means a red rug in a game will naturally "bleed" its color onto the bottom of a nearby white wall—a phenomenon known as indirect lighting. Key Improvements in Version 0.33

The 0.33 update focused on addressing the two primary hurdles of post-process ray tracing: noise and performance.

Advanced Denoising: Ray tracing is inherently "noisy" because it is impossible to calculate an infinite number of rays in real-time. Version 0.33 introduced a more robust temporal denoiser that uses information from previous frames to smooth out the graininess without causing the "ghosting" effects seen in earlier iterations.

Feature Completeness: This version solidified the shader's ability to handle complex light sources, allowing it to interpret game-world UI or glowing objects as emissive light sources that contribute to the global scene illumination.

Accessibility: While native RTX implementations require specific hardware, the RTGI shader is largely hardware-agnostic, running on both NVIDIA and AMD cards, provided the user has sufficient raw processing power. The Visual Impact I’ve written this for a typical PC gaming/graphics

The result is a transformative experience for older titles. Games like Skyrim or The Witcher 3 gain a sense of physical "grounding" that was previously impossible. Objects no longer look like they are floating; they feel integrated into the atmosphere. The 0.33 update specifically helped in making these transitions look natural, moving away from the overly dark, "crushed" shadows of early ray-tracing mods toward a more balanced, cinematic look. Conclusion

The ReShade RTGI 0.33 shader is more than just a graphical "tweak." It represents a bridge between generational gaps in gaming technology. By democratizing global illumination, it allows players to revitalize their favorite classics with modern lighting techniques, proving that the longevity of a game’s visuals is limited only by the creativity of its community.

Worst-case:

Fast first-person shooters (Doom Eternal, Apex) — screen-space artifacts and input lag potential.
Very bright, flat scenes (Fortnite, Overwatch) — the effect becomes subtle to invisible.
Games with heavy depth-of-field — the blur confuses the depth buffer.

Part 3: Step-by-Step Installation Guide (No Black Screens!)

Installing RTGI 0.33 is not as simple as dragging a file into a folder. The author, Marty McFly, distributes his shaders via Patreon (though legacy versions can be found via community archives). Here is the safest, modern way to install it.

Phase 3: Advanced Tuning (The "Secret" to Quality)

This is where most users fail. To make 0.33 look like real path tracing, you have to tune the Light Source.

RTGI doesn't "know" where the sun is. It guesses based on the brightest pixel.

If the image looks too dark: The shader might think a bright wall is the light source, ignoring the sun.
The Solution: Use the Pre-processor Definitions (the box at the top of the settings).
- Look for RESOLUTION_MODE or QUALITY.
- Don't just max this out. Higher quality = significantly lower FPS. For 1440p/4K gaming, "Medium" or "Low" settings often look identical to "High" due to TAA smoothing, but run 20 FPS faster.

Summary: The "Golden Rule" of RTGI

RTGI 0.33 is not a "plug and play" brightness filter. It is a simulation of physics.

Don't try to light the whole scene with it. Let the game's original lighting do the heavy lifting. Use RTGI to fill in the cracks, soften the harsh shadows, and add color bleeding.
Less is more. If you notice the shader immediately, it's set too high. The best RTGI setup is one where you forget it's on, but when you turn it off, the game suddenly looks "flat."

Note: This shader is Patreon-exclusive software. Ensure you are supporting the developer for access to the latest builds and bug fixes.

What is RTGI, exactly?

For the uninitiated, ReShade is a post-processing injection tool. RTGI is a specific shader that uses your GPU’s compute units to simulate Ray Traced Global Illumination.

In simple terms: Light bounces. In vanilla Skyrim, a red brick wall casts a grey shadow. In RTGI, that shadow turns slightly red because the light bounces off the wall onto the floor. This bounce lighting creates depth, realism, and atmosphere that traditional rasterization simply cannot replicate. Survey: Reshade Ray Tracing shader — RTGI 0