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Real-time Ray Tracing

Real-time DXR / Vulkan-RT effects in UE 5.7 that are not Lumen or Path Tracer. These are the standalone RT effects you may still enable for specific high-fidelity needs.

Effects

Effect CVar Status
RT Shadows r.RayTracing.Shadows 1 Production
RT Translucency r.RayTracing.Translucency 1 Production
RT Skylight r.RayTracing.SkyLight 1 Production
RT AO r.RayTracing.AmbientOcclusion 1 Deprecated — prefer Lumen
RT Reflections (standalone) r.RayTracing.Reflections 1 Replaced by Lumen Reflections
RT GI (standalone) r.RayTracing.GlobalIllumination 1 Replaced by Lumen GI

Hardware requirements

  • DX12 + DXR 1.1 (Win10 20H2+, Win11)
  • NVIDIA RTX 2060+, AMD RX 6700+, Arc A series, PS5, Xbox Series X
  • Vulkan with VK_KHR_ray_tracing_pipeline

When to use which

Need Use
GI + reflections Lumen HW RT
Sharp shadows from spot/directional lights RT Shadows
Glass / water with refractions RT Translucency
Skylight contact shadows + AO RT Skylight
Reference frame Path Tracer

Performance

Lever Effect
r.RayTracing.Shadows.Denoiser 2 NRD denoiser path
r.RayTracing.Shadows.SortMaterials 1 Sort hits by material for coherence
r.RayTracing.Geometry.Landscape 0 Skip landscape from BVH if not needed
r.RayTracing.Geometry.NaniteProxies 1 Use Nanite ray-traced proxies

Building the BVH

UE auto-builds a top-level AS (TLAS) every frame and bottom-level (BLAS) on geometry change. For large scenes turn on r.RayTracing.AsyncBuild 1 to overlap BVH builds with the GPU.