Nanite Geometry Collections don't cast shadow in Hardware Ray Tracing

[Danta1ion]

As described in the above image, when I enabled both hardware ray-traced shadow and nanite geometry collection, the shadow disappeared. The nanite geometry only accepts direct lighting from sunlight and point light, without AO and shadow.

Here’s another example of this.

I viewed Unreal Engine source code and found that this issue was caused by FNaniteGeometryCollectionSceneProxy in Engine/Source/Runtime/Experimental/GeometryCollectionEngine/Private/GeometryCollection/GeometryCollectionSceneProxy.h.

This class doesn’t override this function in base class:

void GetDynamicRayTracingInstances(FRayTracingMaterialGatheringContext& Context, TArray<struct FRayTracingInstance>& OutRayTracingInstances) override;

So when ray tracer tries to get the instances of geometry collection, it returns nothing. I found that the latest git commit was in June 2023, and engine developers left a todo comment on FGeometryCollectionSceneProxy, not the nanite one.

Is there any further plan to fix this issue?

[sinigr54]

UE 5.6 same issue

[syngen1]

My geometry collections dont cast shadows from spotlights even with Nanite ticked off. Unless Im doing something else wrong. Is there a way round this while using Lumen? I have a cave that collapses hopefully to block all the light. Its sort of key to the area.

[greatmazingerz]

are your geometry cast shadow activated ? for me HW shadow just dont work .. only some mesh do that random so useless

[greatmazingerz]

Ok i found the bug for me

HW RT shadow dont work not depending nanite or not but depending the texture material

if i use the world grid material it work if i use something else no…..

dont know how to solve yet but that in the material

some material that use almost identical master worr or not work .. that really strange

anyway…. quality on softare shadow look better for me than the jitterring HW one …. so will stick to SW