Blender EEVEE Ray Tracing, Fast GI, and Material Settings Guide

Blender’s online EEVEE guide explains how ray tracing, Fast GI, and material settings work. It lists the relevant settings under the Render › Raytracing and Properties › Material panels. This guide looks at these options in the context of architectural visualization and interior scenes. The guide pages do not specify a particular Blender version, so no version number is given here.

1. Choose a ray-tracing method for your scene

Ray tracing aims to improve the accuracy of indirect lighting by calculating where BSDF rays from surfaces intersect the scene. When it is disabled, Blender switches to a faster method that uses prefiltered light probes. This alternative can be more stable and efficient when visual accuracy is not the priority.

1. Consider the Method option in the Render › Raytracing panel.

2. Light Probe finds scene intersections using light-probe spheres and planes. According to the guide, it has the lowest tracing cost, but relies on probes being placed manually.

3. Screen-Trace traces rays against the screen-space depth buffer. If a ray leaves the viewport, it falls back to light probes. Reflections that depend on geometry not visible on screen therefore cannot always be traced.

When checking surfaces such as glass, glossy furniture, or polished floors in architectural interiors, don’t treat one method as simply “better” or “worse.” Consider the need for reflections in the visible area, the probes placed in the scene, and performance priorities together.

2. Balance resolution and screen-trace precision

Ray-tracing resolution determines the resolution at which the calculation is performed. The guide says that lower settings are faster and use less memory, but can produce a blurrier result. Lower resolution can therefore be useful when testing composition and lighting; check reflection detail in the final image.

When Screen-Trace is enabled, additional tracing settings are available:

• Increasing Precision can improve intersection accuracy and reduce some artifacts, but raises the performance cost and shortens the tracing distance.

• Increasing Thickness can reduce missed intersections. However, reflections may extend and flickering may appear. Lower values can make intersections more accurate, but increase the chance of missing thin surfaces.

• Backface allows rays that hit the back side of visible geometry to be treated as valid. Enabling it can reduce light leaks in screen-space global illumination.

• Radiance Scale adjusts the approximate indirect-light contribution from backface rays. Lower values reduce this contribution; higher values increase it.

The guide does not give a universal “best” value for these settings. In scenes with thin frames, glass panels, or dense geometry, comparing small adjustments through test renders makes it easier to identify each setting’s effect on reflections and light leaks.

3. Manage noise and render cost with Fast GI

Fast GI Approximation uses an approximate calculation as an alternative to ray tracing for BSDFs with high roughness. According to the guide, it can produce less noisy results and capture bounced light more efficiently than tracing individual rays. However, since it is a screen-space effect, it also has related limitations.

Threshold determines the roughness level up to which BSDFs use ray tracing. Rougher surfaces gradually switch to Fast GI; at a value of 1, all surfaces use ray tracing and Fast GI is disabled. If Distance is nonzero, it limits the maximum distance of surfaces that contribute to Fast GI. When changing these settings, check both reflections and indirect lighting; judging by a single test frame may overlook the results on other surfaces.

4. Material thickness and common mistakes

Properties › Material › Thickness approximates an object’s internal structure without resorting to expensive calculations. EEVEE uses this value for effects such as subsurface scattering, the Translucent BSDF, and the Refraction BSDF. If no value is connected to the material node’s output, the default thickness is based on the object’s smallest dimension. A value of zero disables approximate thickness and treats the object as a single interface.

For large or composite meshes, such as vegetation geometry, it may be more appropriate to define the thickness of individual leaves or blades of grass rather than the total thickness of the object. The guide also notes that thickness can be baked into textures or custom attributes for more accurate results. Thickness Mode controls how the value is applied.

Common mistakes:

• Increasing Precision without accounting for the performance cost and shorter tracing distance.

• Setting Thickness too high and overlooking the possibility of elongated reflections or flickering.

• Assuming screen-space ray tracing will always capture geometry outside the view.

• Using a single overall thickness for a composite vegetation mesh without accounting for the separate behavior of individual leaves.

• Assuming EEVEE material settings support all Cycles features; the guide notes that although the two render engines share the same node system, not every feature is supported.

These settings are especially important in architecture, interior design, and archviz workflows involving reflective surfaces, glass, and scenes with dense vegetation. Teams that can manage light probes manually and want lower tracing costs can consider Light Probe; those that need reflections and indirect lighting in screen space should test Screen-Trace and Fast GI options on a scene-by-scene basis. Since the guide specifies no particular hardware model or threshold, decisions should be validated through measurements in the scene being used. Checking EEVEE-specific material behavior and render examples before delivery can also reduce compatibility risks.