When using Weld Simulated Bodies enabled AttachToComponent func, the child Primitive Component's BodyIstance ActorHandle is released. As a result, in BodyInstance.cpp, the judgment of FPhysicsCommand :: ExecuteWrite (ActorHandle, [&] (const FPhysicsActorHandle & Actor) is flipped , and because UpdatePhysicalMaterials does not work, SetPhysMaterialOverride does not function properly.

You should be able to fix this issue by modifying UpdatePhysicalMaterials as follows:


void FBodyInstance::UpdatePhysicalMaterials()
 UPhysicalMaterial* SimplePhysMat = GetSimplePhysicalMaterial();
 TArray<UPhysicalMaterial*> ComplexPhysMats = GetComplexPhysicalMaterials();
//FPhysicsCommand::ExecuteWrite(ActorHandle, [&](const FPhysicsActorHandle& Actor)
 FPhysicsCommand::ExecuteWrite(GetActorReferenceWithWelding(), [&](const FPhysicsActorHandle& Actor)
 ApplyMaterialToInstanceShapes_AssumesLocked(SimplePhysMat, ComplexPhysMats);


Steps to Reproduce
  1. Open SlipTest_4_21 in attached project
  2.  PIE

expect :The box slides in a few seconds

result : The box does NOT slide.

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ComponentUE - Simulation - Physics
Affects Versions4.224.21.2
Target Fix4.23
Fix Commit6544780
Main Commit6903163
CreatedMay 7, 2019
ResolvedMay 17, 2019
UpdatedJun 12, 2019
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