This is a common Mac crash that has affected users since at least 4.14. Unfortunately users have not provided any descriptions of their actions when the crash occurred.
repro steps currently unknown
SEGV_MAPERR at 0x3 UE4Editor-MetalRHI.dylib!FMetalVertexBuffer::FMetalVertexBuffer() UE4Editor-MetalRHI.dylib!FMetalDynamicRHI::RHICreateVertexBuffer() UE4Editor-MetalRHI.dylib!FMetalDynamicRHI::CreateVertexBuffer_RenderThread() UE4Editor-Renderer.dylib!FRWBuffer::Initialize() UE4Editor-Renderer.dylib!FDeferredShadingSceneRenderer::ComputeLightGrid() UE4Editor-Renderer.dylib!FDeferredShadingSceneRenderer::Render() UE4Editor-Renderer.dylib!FRendererModule::BeginRenderingViewFamily(FCanvas*, FSceneViewFamily*)::EURCMacro_FDrawSceneCommand::DoTask() UE4Editor-Renderer.dylib!TGraphTask<FRendererModule::BeginRenderingViewFamily(FCanvas*, FSceneViewFamily*)::EURCMacro_FDrawSceneCommand>::ExecuteTask() UE4Editor-Core.dylib!FNamedTaskThread::ProcessTasksNamedThread() UE4Editor-Core.dylib!FNamedTaskThread::ProcessTasksUntilQuit() UE4Editor-Core.dylib!FTaskGraphImplementation::ProcessThreadUntilRequestReturn() UE4Editor-RenderCore.dylib!RenderingThreadMain() UE4Editor-RenderCore.dylib!FRenderingThread::Run() UE4Editor-Core.dylib!FRunnableThreadPThread::Run() UE4Editor-Core.dylib!FRunnableThreadPThread::_ThreadProc() libsystem_pthread.dylib!<Unknown> libsystem_pthread.dylib!<Unknown> libsystem_pthread.dylib!<Unknown>
Callstack from Log
Reallocating scene render targets to support 16112x6652 NumSamples 1 (Frame:369496). Assertion failed: Assertion failed: InSize <= 256 * 1024 * 1024 [File:/Users/build/Build/++UE4+Release-4.16+Compile/Sync/Engine/Source/Runtime/Apple/MetalRHI/Private/MetalVertexBuffer.cpp] [Line: 20] Metal doesn't support buffers > 256 MB LogCrashTracker: === Critical error: === SIGSEGV: invalid attempt to access memory at address 0x3 FGenericPlatformMisc::RaiseException(unsigned int) Address = 0x97bf00b (filename not found) [in UE4Editor-Core.dylib] FOutputDeviceMacError::Serialize(wchar_t const*, ELogVerbosity::Type, FName const&) Address = 0x99baa2f (filename not found) [in UE4Editor-Core.dylib] FOutputDevice::Logf(wchar_t const*, ...) Address = 0x9a9b6cd (filename not found) [in UE4Editor-Core.dylib] FDebug::AssertFailed(char const*, char const*, int, wchar_t const*, ...) Address = 0x9a0193e (filename not found) [in UE4Editor-Core.dylib] FMetalVertexBuffer::FMetalVertexBuffer(unsigned int, unsigned int) Address = 0x47b1084b (filename not found) [in UE4Editor-MetalRHI.dylib] FMetalDynamicRHI::RHICreateVertexBuffer(unsigned int, unsigned int, FRHIResourceCreateInfo&) Address = 0x47b12437 (filename not found) [in UE4Editor-MetalRHI.dylib] FMetalDynamicRHI::CreateVertexBuffer_RenderThread(FRHICommandListImmediate&, unsigned int, unsigned int, FRHIResourceCreateInfo&) Address = 0x47b12911 (filename not found) [in UE4Editor-MetalRHI.dylib] FRWBuffer::Initialize(unsigned int, unsigned int, EPixelFormat, unsigned int) Address = 0x19bbb887 (filename not found) [in UE4Editor-Renderer.dylib] FDeferredShadingSceneRenderer::ComputeLightGrid(FRHICommandListImmediate&) Address = 0x19d848d7 (filename not found) [in UE4Editor-Renderer.dylib] FDeferredShadingSceneRenderer::Render(FRHICommandListImmediate&) Address = 0x19c9c4f0 (filename not found) [in UE4Editor-Renderer.dylib] FRendererModule::BeginRenderingViewFamily(FCanvas*, FSceneViewFamily*)::EURCMacro_FDrawSceneCommand::DoTask(ENamedThreads::Type, TRefCountPtr<FGraphEvent> const&) Address = 0x1a306790 (filename not found) [in UE4Editor-Renderer.dylib] TGraphTask<FRendererModule::BeginRenderingViewFamily(FCanvas*, FSceneViewFamily*)::EURCMacro_FDrawSceneCommand>::ExecuteTask(TArray<FBaseGraphTask*, FDefaultAllocator>&, ENamedThreads::Type) Address = 0x1a367d13 (filename not found) [in UE4Editor-Renderer.dylib] FNamedTaskThread::ProcessTasksNamedThread(int, bool) Address = 0x97df6cf (filename not found) [in UE4Editor-Core.dylib] FNamedTaskThread::ProcessTasksUntilQuit(int) Address = 0x97db5d5 (filename not found) [in UE4Editor-Core.dylib] FTaskGraphImplementation::ProcessThreadUntilRequestReturn(ENamedThreads::Type) Address = 0x97d7e11 (filename not found) [in UE4Editor-Core.dylib] RenderingThreadMain(FEvent*) Address = 0xf8e0d72 (filename not found) [in UE4Editor-RenderCore.dylib] FRenderingThread::Run() Address = 0xf8f58e7 (filename not found) [in UE4Editor-RenderCore.dylib] FRunnableThreadPThread::Run() Address = 0x98407f0 (filename not found) [in UE4Editor-Core.dylib] FRunnableThreadPThread::_ThreadProc(void*) Address = 0x97fab30 (filename not found) [in UE4Editor-Core.dylib] _pthread_body() Address = 0xd4f7393b (filename not found) [in libsystem_pthread.dylib] _pthread_body() Address = 0xd4f73887 (filename not found) [in libsystem_pthread.dylib] thread_start() Address = 0xd4f7308d (filename not found) [in libsystem_pthread.dylib]
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-47688 in the post.