How to make buoyancy work?

Development Programming & Scripting Blueprint
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1

Hi, I’ve been trying to make buoyancy work, but I haven’t been successful.

I’m using UE5.1

I have my static mesh set to:

  • Movable
  • Mass: 100KG
  • Collision: PhysicsActor
  • Simulate Physics Enabled
  • Pontoons are set up.

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For the water, I’m using the Epic Games Water Plugin.
Ocean body is set to:

  • Collision: WaterBodyCollision

When I press play, the boat always sinks. I added some nodes to debug, it seems that the “boat” doesn’t recognize the water, or vice versa.

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2

Generate Overlap Events is also enabled.

I tried using BP example from the water plugin, it’s also sinking. I checked the other threads, and collision profile is set up.

3

I re-added the Ocean body, and buoyancy have started to make an impact. Although it’s now making the boat a ragdoll:

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I’ve assigned the pontoons on specific, proportional sockets:

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4

If I scale my boat back to 1.0, the pontoons seem to work, although the boat is still semi-underwater.

If I scale it to my desired size of 10, it sinks as if the pontoons don’t do anything. Mass scaling is turned off, but it looks like there’s another configuration has to be adjusted.

5

Hey there @Rvx28! Welcome to the community! Scale shouldn’t have an effect, only mass if Mass Scaling is off, so that’s definitely odd! Check if the amount of force being put out is more or less when it comes to the larger scaled variant by taking the pontoons and logging their force. It might give us some insight:

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In my case, scale has 0 effect on if an object will float since the mass is locked at a flat 50.
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6

What I do is use box collider for simulating physics and as base to attach meshes to, all static meshes mass set to 0 or they will mess it up.

1 Like
7

I unfortunately have the same “Crysis frog space adventure” issue:

Also using simple physics, collision and socket based settings:

2023-04-03 18_26_17-SailingShip
2023-04-03 18_26_17-SailingShip1403×896 91.3 KB

2023-04-03 18_28_14-SailingShip_Floating_BP
2023-04-03 18_28_14-SailingShip_Floating_BP696×404 8.53 KB

2023-04-03 18_28_46-SailingShip_Floating_BP
2023-04-03 18_28_46-SailingShip_Floating_BP704×743 16.5 KB

I wish I could understand why my ship flies so high to the sky…

8

You might try increasing the mass, 100kg for 4x100cm pontoons sounds bouncy. Also if your collider mesh isn’t symmetrical it will make it unevenly balanced. I suggest starting with simple shape and then experiment with ‘real’ ship.

1 Like
9

My fix was making sure my root in my blueprint is not a scene component. I made it my static mesh.

10

just in case..

water plugin buoyancy check list that worked in 5.6.1:

  1. collision preset “WaterBodyCollision” on your river/ocean/etc.
  2. place actor above water
  3. auto activate buoyancy component
  4. SM: static mesh as root component
  5. SM: simulate physics and mass on static mesh
  6. reasonable pontoons quantity (at least three for plane)
  7. buoyancy: relative locations for pontoons in component instead sockets on static mesh
  8. collision preset with Quary and Physics on static mesh or just PhysicsActor
  9. buoyancy: “apply drag forces in water” to make your actor less jumpy in water
  10. buoyancy: uncheck “Center Pontoons on COM” if your actor pivot not in center of mass, because it will shift your relative locations of pontoons and actor can turn over in water
  11. some tribal dance with properties: mass, buoyancy coeffficient, pontoons radius

There is some problem with pontoons on sockets or I doing it wrong, please correct me if I wrong.

Whenewer I use sockets with same locations that in buoyancy component i get ensureMsgf here:

https://github.com/EpicGames/UnrealEngine/blob/release/Engine/Plugins/Experimental/Water/Source/Runtime/Private/BuoyancyComponent.cpp#L419

LogOutputDevice: Error: === Handled ensure: ===
LogOutputDevice: Error: Ensure condition failed: ComputeSuccess  [File:D:\build\++UE5\Sync\Engine\Plugins\Experimental\Water\Source\Runtime\Private\BuoyancyComponent.cpp] [Line: 419] 
LogOutputDevice: Error: Failed to compute 4 sprung masses for: BP_Pawn
LogOutputDevice: Error: ErrMsg: "Spring configuration is invalid! Please make sure the center of mass is located inside the area covered by the springs."
LogOutputDevice: Error: Stack: 
LogOutputDevice: Error: [Callstack] 0x00007ffefabdb32e UnrealEditor-Water.dll!`Chaos::FSimCallbackCommandObject::OnPreSimulate_Internal'::`6'::<lambda_1>::operator()() [D:\build\++UE5\Sync\Engine\Plugins\Experimental\Water\Source\Runtime\Private\BuoyancyComponent.cpp:419]
LogOutputDevice: Error: [Callstack] 0x00007ffefaa69ea2 UnrealEditor-Water.dll!UBuoyancyComponent::ComputePontoonCoefficients() [D:\build\++UE5\Sync\Engine\Plugins\Experimental\Water\Source\Runtime\Private\BuoyancyComponent.cpp:419]
LogOutputDevice: Error: [Callstack] 0x00007ffefaaaed9b UnrealEditor-Water.dll!UBuoyancyComponent::Update() [D:\build\++UE5\Sync\Engine\Plugins\Experimental\Water\Source\Runtime\Private\BuoyancyComponent.cpp:150]
LogOutputDevice: Error: [Callstack] 0x00007ffeffa2faf3 UnrealEditor-Engine.dll!TSet<TTuple<unsigned __int64,UAudioComponent * __ptr64>,TDefaultMapHashableKeyFuncs<unsigned __int64,UAudioComponent * __ptr64,0>,FDefaultSetAllocator>::Emplace<TPairInitializer<unsigned __int64 const & __ptr64,UAudioComponent * __ptr64 && __ptr64> >() [D:\build\++UE5\Sync\Engine\Source\Runtime\Engine\Classes\GameFramework\Actor.h:4835]
LogOutputDevice: Error: [Callstack] 0x00007ffeffc2a149 UnrealEditor-Engine.dll!FActorComponentTickFunction::ExecuteTick() [D:\build\++UE5\Sync\Engine\Source\Runtime\Engine\Private\Components\ActorComponent.cpp:1589]
LogOutputDevice: Error: [Callstack] 0x00007fff015d13e5 UnrealEditor-Engine.dll!TGraphTask<FTickFunctionTask>::ExecuteTask() [D:\build\++UE5\Sync\Engine\Source\Runtime\Core\Public\Async\TaskGraphInterfaces.h:706]
LogOutputDevice: Error: [Callstack] 0x00007fff57d7fb72 UnrealEditor-Core.dll!UE::Tasks::Private::FTaskBase::TryExecuteTask() [D:\build\++UE5\Sync\Engine\Source\Runtime\Core\Public\Tasks\TaskPrivate.h:527]
LogOutputDevice: Error: [Callstack] 0x00007fff57d7284f UnrealEditor-Core.dll!FNamedTaskThread::ProcessTasksNamedThread() [D:\build\++UE5\Sync\Engine\Source\Runtime\Core\Private\Async\TaskGraph.cpp:779]
LogOutputDevice: Error: [Callstack] 0x00007fff57d72d69 UnrealEditor-Core.dll!FNamedTaskThread::ProcessTasksUntilIdle() [D:\build\++UE5\Sync\Engine\Source\Runtime\Core\Private\Async\TaskGraph.cpp:679]
LogOutputDevice: Error: [Callstack] 0x00007fff57d73496 UnrealEditor-Core.dll!FTaskGraphCompatibilityImplementation::ProcessUntilTasksComplete() [D:\build\++UE5\Sync\Engine\Source\Runtime\Core\Private\Async\TaskGraph.cpp:1592]
LogOutputDevice: Error: [Callstack] 0x00007fff015f42b4 UnrealEditor-Engine.dll!FTickTaskSequencer::ReleaseTickGroup() [D:\build\++UE5\Sync\Engine\Source\Runtime\Engine\Private\TickTaskManager.cpp:986]
LogOutputDevice: Error: [Callstack] 0x00007fff015fd506 UnrealEditor-Engine.dll!FTickTaskManager::RunTickGroup() [D:\build\++UE5\Sync\Engine\Source\Runtime\Engine\Private\TickTaskManager.cpp:2079]
LogOutputDevice: Error: [Callstack] 0x00007fff005f1def UnrealEditor-Engine.dll!UWorld::RunTickGroup() [D:\build\++UE5\Sync\Engine\Source\Runtime\Engine\Private\LevelTick.cpp:786]
LogOutputDevice: Error: [Callstack] 0x00007fff005fd81e UnrealEditor-Engine.dll!UWorld::Tick() [D:\build\++UE5\Sync\Engine\Source\Runtime\Engine\Private\LevelTick.cpp:1511]
LogOutputDevice: Error: [Callstack] 0x00007fff50c83474 UnrealEditor-UnrealEd.dll!UEditorEngine::Tick() [D:\build\++UE5\Sync\Engine\Source\Editor\UnrealEd\Private\EditorEngine.cpp:2151]
LogOutputDevice: Error: [Callstack] 0x00007fff51955956 UnrealEditor-UnrealEd.dll!UUnrealEdEngine::Tick() [D:\build\++UE5\Sync\Engine\Source\Editor\UnrealEd\Private\UnrealEdEngine.cpp:533]
LogOutputDevice: Error: [Callstack] 0x00007ff646649ce4 UnrealEditor.exe!FEngineLoop::Tick() [D:\build\++UE5\Sync\Engine\Source\Runtime\Launch\Private\LaunchEngineLoop.cpp:5625]
LogOutputDevice: Error: [Callstack] 0x00007ff64666e5ac UnrealEditor.exe!GuardedMain() [D:\build\++UE5\Sync\Engine\Source\Runtime\Launch\Private\Launch.cpp:187]
LogOutputDevice: Error: [Callstack] 0x00007ff64666e6ba UnrealEditor.exe!GuardedMainWrapper() [D:\build\++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:128]
LogOutputDevice: Error: [Callstack] 0x00007ff64667209e UnrealEditor.exe!LaunchWindowsStartup() [D:\build\++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:282]
LogOutputDevice: Error: [Callstack] 0x00007ff646684e44 UnrealEditor.exe!WinMain() [D:\build\++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:339]
LogOutputDevice: Error: [Callstack] 0x00007ff6466880fa UnrealEditor.exe!__scrt_common_main_seh() [D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288]
LogOutputDevice: Error: [Callstack] 0x00007fff944c7374 KERNEL32.DLL!UnknownFunction []
LogOutputDevice: Error: [Callstack] 0x00007fff9635cc91 ntdll.dll!UnknownFunction []

I’ve tried to change “center of mass of offset” for SM but it didn’t help, so I leave it with relative pontoons locations in component instead SM sockets