Async Physics in C++ (works in Blueprint)

[gabbott]

I’m attempting to write some flight physics in a AsyncPhysicsTick, and the following works:

However, I can’t figure out how to make the same work in C++.

I’m able to have the code above run on an Actor, but I can’t figure out how to AddForce or AddImpulse.

In a previous experiment, I attempted to use a Primative movement component to put the logic there, and while I --thought-- I found a way to correctly call things:

I ended up with compilation errors that I wasn’t able to understand:

FlightModelComponent.cpp.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) private: static unsigned int & __cdecl TThreadSingleton<class Chaos::FPhysicsThreadContext>::GetTlsSlot(void)" (__imp_?GetTlsSlot@?$TThreadSingleton@VFPhysicsThreadContext@Chaos@@@@CAAEAIXZ) referenced in function "public: virtual void __cdecl UFlightModelComponent::AsyncPhysicsTickComponent(float,float)" (?AsyncPhysicsTickComponent@UFlightModelComponent@@UEAAXMM@Z)
Display      LogLiveCoding             FlightModelComponent.cpp.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) public: __cdecl Chaos::FPhysicsThreadContext::FPhysicsThreadContext(void)" (__imp_??0FPhysicsThreadContext@Chaos@@QEAA@XZ) referenced in function "public: static class FTlsAutoCleanup * __cdecl UE::Core::Private::Function::TFunctionRefCaller<class `public: static class Chaos::FPhysicsThreadContext & __cdecl TThreadSingleton<class Chaos::FPhysicsThreadContext>::Get(void)'::`2'::<lambda_1>,class FTlsAutoCleanup * __cdecl(void)>::Call(void *)" (?Call@?$TFunctionRefCaller@V<lambda_1>@?1??Get@?$TThreadSingleton@VFPhysicsThreadContext@Chaos@@@@SAAEAVFPhysicsThreadContext@Chaos@@XZ@$$A6APEAVFTlsAutoCleanup@@XZ@Function@Private@Core@UE@@SAPEAVFTlsAutoCleanup@@PEAX@Z)
Display      LogLiveCoding             FlightModelComponent.cpp.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) public: virtual __cdecl Chaos::FPhysicsThreadContext::~FPhysicsThreadContext(void)" (__imp_??1FPhysicsThreadContext@Chaos@@UEAA@XZ) referenced in function "public: virtual void * __cdecl Chaos::FPhysicsThreadContext::`scalar deleting destructor'(unsigned int)" (??_GFPhysicsThreadContext@Chaos@@UEAAPEAXI@Z)
Display      LogLiveCoding             FlightModelComponent.cpp.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) void __cdecl Chaos::SetObjectStateHelper(class IPhysicsProxyBase &,class Chaos::TPBDRigidParticleHandleImp<double,3,1> &,enum Chaos::EObjectStateType,bool,bool)" (__imp_?SetObjectStateHelper@Chaos@@YAXAEAVIPhysicsProxyBase@@AEAV?$TPBDRigidParticleHandleImp@N$02$00@1@W4EObjectStateType@1@_N3@Z) referenced in function "public: virtual void __cdecl UFlightModelComponent::AsyncPhysicsTickComponent(float,float)" (?AsyncPhysicsTickComponent@UFlightModelComponent@@UEAAXMM@Z)
Display      LogLiveCoding             FlightModelComponent.cpp.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) public: void __cdecl Chaos::FRewindData::MarkDirtyFromPT(class Chaos::TGeometryParticleHandleImp<double,3,1> &)" (__imp_?MarkDirtyFromPT@FRewindData@Chaos@@QEAAXAEAV?$TGeometryParticleHandleImp@N$02$00@2@@Z) referenced in function "public: virtual void __cdecl UFlightModelComponent::AsyncPhysicsTickComponent(float,float)" (?AsyncPhysicsTickComponent@UFlightModelComponent@@UEAAXMM@Z)
Display      LogLiveCoding             D:\round2\vr_office\Binaries\Win64\UnrealEditor-vr_office.patch_6.exe : fatal error LNK1120: 5 unresolved externals

So my question is, what struct or class do I use to apply force or impulse? Do i get a reference to the root component and then apply it there? Thank you in advance.

[gabbott]

I was able to this working:

However, I’m not exactly sure if this is the right way forward, any input would be welcomed!

[MostHost_LA]

If you want the exact same behaviour, double click the BP nodes and read the resulting Kismeth functions to see their logic.

Your handle and system is definitely diverged from what the BP version shows (and that may not necessarily be a bad thing).

[gabbott]

Understood, thank you for the tip!