Hi.
Looks like those “horrible shadows” were fixed in the 5.3.0-preview1.
On the 5.3.1 I’ve tested also VULKAN_SM6 and Path Tracing is still not working properly. It’s easy to test even on the “clean” new UE project.
There are requirements for the Windows on the Path Tracer page Path Tracer in Unreal Engine | Unreal Engine 5.3 Documentation but still the option is available on the Linux.
There are few mentions about “HitGroupSystemIndexBuffer” in the UE source but that didn’t bring me closer to solving that puzzle.
Looks like Material shaders should get compiler for the path tracer (ray tracer? they have partially shared code) but since the “invalid parameter” HitGroupSystemIndexBuffer appears, then the shaders cannot be compiled and Material is replaced by the default one (if the default one is defined and can be compiled) or empty one. Then this scene is pushed to the Path Tracer which traces “nothing”.
It’s very probable the Path Tracing is working but the Vulkan shader compilation is somehow broken.