Modular Character and complex collision trace

Development Programming & Scripting C++
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1

Hello all!
I am having a problem using the skeletal mesh merge illustrated here Working with Modular Characters | Unreal Engine Documentation with complex collision. The Merge mesh code is the same as the one in the page, called from a class that extends ACharacter.

Then my collision on the actor supposed to trace is set up as follows:

	FCollisionQueryParams QueryParams;
	QueryParams.AddIgnoredActor(this);
	QueryParams.bReturnPhysicalMaterial = true;
	QueryParams.bTraceComplex = true; 
	const bool Result = GetWorld()->LineTraceSingleByChannel(HitResult, EyesPosition, TraceEnd, ECC_GameTraceChannel2, QueryParams);

This is the function that builds the character mesh (I left an option to disable the modular character and use the default mesh):

void ASOComposableCharacter::RebuildCharacterMesh()
{
	if (this->bIsComposabeCharacter)
	{
		ECollisionEnabled::Type CurrentCollisionEnabled = GetMesh()->GetCollisionEnabled();
		ECollisionResponse CurrentCollisionResponse = GetMesh()->GetCollisionResponseToChannel(ECC_GameTraceChannel2);
		
		for (auto& Elem : ComposableParts) {
			if (Elem.Value.CurrentPart)
			{
				Elem.Value.CurrentPart->bEnablePerPolyCollision = true;
				SkeletalMeshMergeParams.MeshesToMerge.Add(Elem.Value.CurrentPart);
			} else
			{
				// Apply default part
				Elem.Value.DefaultPart->bEnablePerPolyCollision = true;
				SkeletalMeshMergeParams.MeshesToMerge.Add(Elem.Value.DefaultPart);
			}
		}
		
		USkeletalMesh* ComposedMesh = USOMeshMergeFunctionLibrary::MergeMeshes(SkeletalMeshMergeParams);
		GetMesh()->SetSkeletalMesh(ComposedMesh);
		GetMesh()->SetCollisionEnabled(CurrentCollisionEnabled);
		GetMesh()->SetCollisionResponseToChannel(ECC_GameTraceChannel2, CurrentCollisionResponse);
	}
}

The issue is that when bIsComposableCharacter is false (so when it uses the default mesh) everything works. When I enable it, apparently the collision trace does not intercept the mesh.

Form a further test, it seems that the whole new mesh does not collide with anything, despite my call to SetCollisionEnabled. Reducing the capsule radius to a small number, my other character is able to walk through the mesh.

Any hint?

Thanks!

Stefano

2

I have the same issue, neither simple nor complex collision works. There is no collision at all. The Comparison Chart at the bottom of the Documentation page however suggest, that physics should work with Mesh Merge.
Does no one have an idea?