I’m trying to write an actor component that will dynamically swap the texture that’s being applied to an actor. When I run my project, however, it immediately crashes with this error:
Unhandled exception at 0x000007FED8FF8600 (UE4Editor-Engine.dll) in UE4Editor.exe: 0xC0000005: Access violation writing location 0x000000000000015B.
Some background:
- My component has a parameter called BaseMaterial, and the material I’m pointing it to has a TextureSampleParameter called “texture”
- My component has a hidden parameter called MtlInst of type UMaterialInstanceDynamic*
- If it matters, the component is being applied to a DecalActor to try to change the decal material that’s being used.
Here are the applicable bits from my ActorComponent code:
UTexture2D* LoadTextureRefFromPath(const FString& path)
{
if (path.IsEmpty())
return NULL;
return Cast<UTexture2D>(StaticLoadObject(UTexture2D::StaticClass(), NULL, *(path)));
}
void UMyActorComponent::BeginPlay()
{
Super::BeginPlay();
// ...
if (!MtlInst)
{
MtlInst = ((UStaticMeshComponent*)GetOwner())->CreateAndSetMaterialInstanceDynamicFromMaterial(0, BaseMaterial);
}
}
void UMyActorComponent::SwapTexture()
{
FString texPath = "Texture2D'/Game/Textures/test_texture.test_texture'";
UTexture2D* tex = LoadTextureRefFromPath(texPath);
if (tex)
{
if (!MtlInst)
{
UE_LOG(LogTemp, Warning, TEXT("MtlInst is undefined!"));
}
else
{
MtlInst->SetTextureParameterValue(FName("texture"), tex);
}
}
else
{
FString msg = "Unable to find texture: " + texPath;
UE_LOG(LogTemp, Warning, TEXT("%s"), *msg);
}
}
The crash occurs when it hits the SetTextureParameterValue call. Does anyone see anything that might cause a crash in there?
Here’s the stack trace, if it helps:
UE4Editor_Engine!FMaterialRenderProxy::InvalidateUniformExpressionCache() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.9\engine\source\runtime\engine\private\materials\materialshared.cpp:1652]
UE4Editor_Engine!FMaterialInstanceResource::RenderThread_UpdateParameter<UTexture const * __ptr64>() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.9\engine\source\runtime\engine\private\materials\materialinstancesupport.h:118]
UE4Editor_Engine!EURCMacro_SetMIParameterValue<FTextureParameterValue>::DoTask() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.9\engine\source\runtime\engine\private\materials\materialinstance.cpp:322]
UE4Editor_Engine!TGraphTask<EURCMacro_SetMIParameterValue<FTextureParameterValue> >::ExecuteTask() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.9\engine\source\runtime\core\public\async\taskgraphinterfaces.h:779]
UE4Editor_Core!FTaskThread::ProcessTasks() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.9\engine\source\runtime\core\private\async\taskgraph.cpp:539]
UE4Editor_Core!FTaskThread::ProcessTasksUntilQuit() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.9\engine\source\runtime\core\private\async\taskgraph.cpp:340]
UE4Editor_RenderCore!RenderingThreadMain() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.9\engine\source\runtime\rendercore\private\renderingthread.cpp:310]
UE4Editor_RenderCore!FRenderingThread::Run() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.9\engine\source\runtime\rendercore\private\renderingthread.cpp:411]
UE4Editor_Core!FRunnableThreadWin::Run() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.9\engine\source\runtime\core\private\windows\windowsrunnablethread.cpp:74]
Here’s the stacktrace, if it helps:
UE4Editor_Engine!FMaterialRenderProxy::InvalidateUniformExpressionCache() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.9\engine\source\runtime\engine\private\materials\materialshared.cpp:1652]
UE4Editor_Engine!FMaterialInstanceResource::RenderThread_UpdateParameter<UTexture const * __ptr64>() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.9\engine\source\runtime\engine\private\materials\materialinstancesupport.h:118]
UE4Editor_Engine!EURCMacro_SetMIParameterValue<FTextureParameterValue>::DoTask() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.9\engine\source\runtime\engine\private\materials\materialinstance.cpp:322]
UE4Editor_Engine!TGraphTask<EURCMacro_SetMIParameterValue<FTextureParameterValue> >::ExecuteTask() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.9\engine\source\runtime\core\public\async\taskgraphinterfaces.h:779]
UE4Editor_Core!FTaskThread::ProcessTasks() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.9\engine\source\runtime\core\private\async\taskgraph.cpp:539]
UE4Editor_Core!FTaskThread::ProcessTasksUntilQuit() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.9\engine\source\runtime\core\private\async\taskgraph.cpp:340]
UE4Editor_RenderCore!RenderingThreadMain() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.9\engine\source\runtime\rendercore\private\renderingthread.cpp:310]
UE4Editor_RenderCore!FRenderingThread::Run() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.9\engine\source\runtime\rendercore\private\renderingthread.cpp:411]
UE4Editor_Core!FRunnableThreadWin::Run() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.9\engine\source\runtime\core\private\windows\windowsrunnablethread.cpp:74]
Seems like decal actors may be unique enough to not work with the generic casting/assigning that I was trying to do. I switched the BeginPlay() code to this:
if (!MtlInst)
{
UDecalComponent* decal = Cast<ADecalActor>(GetOwner())->GetDecal();
MtlInst = UMaterialInstanceDynamic::Create(decal->GetDecalMaterial(), this);
if (!MtlInst)
{
UE_LOG(LogTemp, Warning, TEXT("MtlInst wasn't initialized!!!!"));
return;
}
decal->SetDecalMaterial(MtlInst);
}
And it seems to be much happier - no crashes and the texture swaps out correctly!