Ray Tracing Features Settings | Unreal Engine 4.27 Documentation

In this page you'll find the properties and settings available for the Ray Tracer and Path Tracer features.

Post Process Volume

Use the following properties for Post Process Volumes to affect Ray Tracing features.

Property	Description
Ambient Occlusion
Intensity	Defines how much ambient occlusion affects non-direct lighting for Ray Traced Ambient Occlusion. Lower values decrease the effect while higher values increase how strong the effect is.
Radius	Controls the distance in Unreal Units that ambient occlusion affects.
Ray Tracing Ambient Occlusion
Enabled	When the checkbox is checked, it enables Ray Tracing Ambient Occlusion (RTAO).
Samples Per Pixel	Sets the number of samples to use per pixel for Ray Traced Ambient Occlusion (RTAO). Additional samples decrease performance while increasing quality and accuracy. Set to 1 sample per pixel by default.
Ray Tracing Global Illumination
Type	Sets what Ray Tracing Global Illumination to use: Disabled: Disables RTGI methods. Brute Force: Uses the slower, more accurate brute force method for dynamic indirect lighting using RTGI. Final Gather: Uses a faster, less accurate final gather method for dynamic indirect lighting using RTGI. For more information, see the Ray Traced Global Illumination section of the Real-Time Ray Tracing page.
Enabled	When the checkbox is checked, it enables Ray Tracing Global Illumination (RTGI).
Max Bounces	Sets the maximum number of bounces of light that will be used by RTGI.
Samples Per Pixel	Sets the number of samples to use per pixel for RTGI. Additional samples decrease performance while increasing quality and accuracy. Set to 1 sample per pixel by default.
Reflections
Type	Sets whether to use Ray Tracing or Screen Space method for reflections within this volume. When selecting Raster, Screen Space Reflections (SSR) instead of raytraced ones.
Ray Tracing Reflections
Max Roughness	Sets the maximum roughness value that Ray Traced Reflections will be visible before falling back to raster methods that are less expensive. Reflection contribution is smoothly faded when close to the roughness threshold and this parameter behaves similarly to SSR’s Max Roughness setting. Lower values fall back to other methods more quickly.
Max Bounces	Sets the maximum number of bounces that Ray Traced Reflections uses. More bounces create inter-reflection but comes at a higher cost. Set to 1 bounce by default.
Samples Per Pixel	Sets the number of samples to use per pixel for Ray Traced Reflections. Additional samples decrease performance while increasing quality and accuracy. Set to 1 sample per pixel by default.
Shadows	Sets how shadows should be reflected. Choose between: Hard Shadows which has no soft shadows Area Shadows to have soft shadowing like raytraced shadows Disable to disable shadowing in Ray Traced Reflections
Include Translucent Objects	When the checkbox is checked, this sets whether translucent materials will be included in Ray Tracing Reflections.
Translucency
Type	Sets whether to use Ray Tracing or Raster method for reflections within this volume. When selecting Raster, default translucency methods will be used instead of ray traced ones.
Ray Tracing Translucency
Max Roughness	Sets the maximum roughness value that Ray Traced Translucency will be visible before falling back to raster methods that are less expensive. Translucency contribution is smoothly faded when close to the roughness threshold and this parameter behaves similarly to SSR’s Max Roughness setting. Lower values fall back to other methods more quickly.
Max Refraction Rays	Sets the maximum number of refraction rays that Ray Traced Translucency uses. Additional Samples decrease performance while increasing quality and accuracy. Set to 3 refraction rays by default.
Samples Per Pixel	Sets the number of samples to use per pixel for Ray Traced Translucency. Additional samples decrease performance while increasing quality and accuracy. Set to 1 sample per pixel by default.
Shadows	Sets how shadows should be reflected. Choose between: Hard Shadows which has no soft shadows Area Shadows to have soft shadowing like raytraced shadows Disable to disable shadowing in Ray Traced Translucency
Refraction	Sets whether refraction should be enabled or not for Ray Traced Translucency. If disabled, rays will not scatter and only travel in the same direction as before the intersection event.
Path Tracing
Max Bounces	Sets the maximum number of bounces that the Path Tracer uses.
Samples Per Pixel	Sets the number of samples to use per pixel for the Path Tracer.

Types of Lights

Directional Light

Use the following properties for Directional Lights to affect Ray Tracing features.

Property	Description
Light
Source Angle	The angle subtended by light source in degrees (also known as angular diameter). Lower angles give sharper shadow contacts whereas higher degree angles give softer shadows.
Cast Ray Traced Shadow	Whether the light shadows are computed with shadowmapping or ray tracing.
Affect Ray Tracing Reflections	Whether the light affects objects in reflections when Ray Traced Reflections is enabled.
Affect Ray Tracing Global Illumination	Whether the light contributes to ray traced global illumination when Ray Tracing Global Illumination is enabled.
Ray Tracing
Samples Per Pixel	Sets the number of samples to use per pixel for Ray Traced Shadows from a Directional Light. Additional samples decrease performance while increasing quality and accuracy. Set to 1 sample per pixel by default.

Point and Spot Lights

Use the following properties for Point and Spot Lights to affect Ray Tracing features.

Property	Description
Light
Source Radius	The radius of the light sources shape. A smaller radius gives sharper shadow contacts whereas a higher radius gives softer shadows.
Cast Ray Traced Shadow	Whether the light shadows are computed with shadowmapping or ray tracing.
Affect Ray Tracing Reflections	Whether the light affects objects in reflections when Ray Traced Reflections is enabled.
Affect Ray Tracing Global Illumination	Whether the light contributes to ray traced global illumination when Ray Tracing Global Illumination is enabled.
Ray Tracing
Samples Per Pixel	Sets the number of samples to use per pixel for Ray Traced Shadows from Point and Spot Lights. Additional samples decrease performance while increasing quality and accuracy. Set to 1 sample per pixel by default.

Rect Light

Use the following properties for Rect Lights to affect Ray Tracing features.

Property	Description
Light
Source Width	The width of the light source shape.
Source Height	The height of the light source shape.
Barn Door Angle	The angle of the barn door attached to the light source.
Barn Door Length	The length of the barn door attached to the light source.
Cast Ray Traced Shadow	Whether the light shadows are computed with shadowmapping or ray tracing.
Affect Ray Tracing Reflections	Whether the light affects objects in reflections when Ray Traced Reflections is enabled.
Affect Ray Tracing Global Illumination	Whether the light contributes to ray traced global illumination when Ray Tracing Global Illumination is enabled.
Ray Tracing
Samples Per Pixel	Sets the number of samples to use per pixel for Ray Traced Shadows from a Rect Light. Additional samples decrease performance while increasing quality and accuracy. Set to 1 sample per pixel by default.

Sky Light

Use the following properties for the Sky Light to affect Ray Tracing features.

Property	Description
Light
Cast Ray Traced Shadow	Whether the light shadows are computed with shadowmapping or ray tracing.
Affect Ray Tracing Reflections	Whether the light affects objects in reflections when Ray Traced Reflections is enabled.
Affect Ray Tracing Global Illumination	Whether the light contributes to ray traced global illumination when Ray Tracing Global Illumination is enabled.
Ray Tracing
Samples Per Pixel	Sets the number of samples to use per pixel for Ray Traced Shadows from a Sky Light. Additional samples decrease performance while increasing quality and accuracy. Set to 1 sample per pixel by default.

Actors

Use the following properties for Actors to affect Ray Tracing features.

Property	Description
Light
Evaluate World Position Offset	When enabled, this Actor will be evaluated for ray tracing effects for any assigned Materials that make use of World Position Offset.
Visible in Ray Tracing	When enabled, this component will be visible in ray tracing effects. When disabled, it will be removed from ray tracing effects like reflections, translucency, shadows, and more.

Materials

use the following properties for Materials to affect Ray Tracing features.

Property	Description
Material
Cast Ray Traced Shadows	Set whether this Material should cast ray traced shadows when Ray Tracing features are enabled.