Only point lights affect indirect lighting on RTGI much less than other types of lights.
[Link Removed]
Indirect lighting of baked lightmaps look much stronger than RTGI.
[Link Removed]
Apparently, it's because only point lights are divided by 4*PI in SetupLightParameters of Engine\Source\Runtime\Renderer\Private\RayTracing\RayTracingGlobalIllumination.cpp
case LightType_Point: default: { LightParameters->Type[LightParameters->Count] = 1; LightParameters->Position[LightParameters->Count] = LightShaderParameters.Position; // #dxr_todo: UE-72556 define these differences from Lit.. LightParameters->Color[LightParameters->Count] = LightShaderParameters.Color / (4.0 * PI); float SourceRadius = 0.0; // LightShaderParameters.SourceRadius causes too much noise for little pay off at this time LightParameters->Dimensions[LightParameters->Count] = FVector(0.0, 0.0, SourceRadius); LightParameters->Attenuation[LightParameters->Count] = 1.0 / LightShaderParameters.InvRadius; break; }
I removed the 4*PI then it fixed this issue and indirect lighting from a point light on RTGI looks more similar to baked lighting. (Shelved CL: 14023328 on 4.25plus)
[Link Removed]
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-96362 in the post.