Method Update

trinityal/dx12/Tr2RtTopLevelAccelerationStructureALDx12.cpp:174–262

DXR suggests to rebuild the TLAS every frame instead of updating it

// DXR suggests to rebuild the TLAS every frame instead of updating it
ALResult Tr2RtTopLevelAccelerationStructureAL::Update( const size_t count, const Tr2RtInstanceAL* instances, Tr2RenderContextAL& renderContext )
{
	if( !IsValid() )
	{
		return E_INVALIDCALL;
	}
	if( !renderContext.IsValid() )
	{
		return E_INVALIDARG;
	}
	if( m_capacity < count )
	{
		return E_INVALIDARG;
	}
	if( !renderContext.m_commandList4 )
	{
		return E_INVALIDCALL;
	}

	//if this causes problems then create an array of all the instances.blas buffers fill the uav barrier with that
	D3D12_RESOURCE_BARRIER uavBarrier;
	uavBarrier.Type = D3D12_RESOURCE_BARRIER_TYPE_UAV;
	uavBarrier.UAV.pResource = nullptr;
	uavBarrier.Flags = D3D12_RESOURCE_BARRIER_FLAG_NONE;
	renderContext.m_commandList->ResourceBarrier( 1, &uavBarrier );

	CComPtr<ID3D12Resource> uploadBuffer;
	auto completed = m_owner->GetRenderedFrameNumber();
	for( auto it = begin( m_uploadBuffers ); it != end( m_uploadBuffers ); ++it )
	{
		if( completed >= it->frameIndex )
		{
			uploadBuffer = it->uploadBuffer;
			it->frameIndex = m_owner->GetRecordingFrameNumber();
			break;
		}
	}
	if( !uploadBuffer )
	{
		auto uploadHeap = TrinityALImpl::HeapDesc( D3D12_HEAP_TYPE_UPLOAD );
		auto uploadDesc = TrinityALImpl::BufferDesc( sizeof( D3D12_RAYTRACING_INSTANCE_DESC ) * m_capacity, D3D12_RESOURCE_FLAG_NONE );
		CR_RETURN_HR( m_owner->m_device->CreateCommittedResource(
			&uploadHeap,
			D3D12_HEAP_FLAG_NONE,
			&uploadDesc,
			D3D12_RESOURCE_STATE_GENERIC_READ,
			nullptr,
			IID_PPV_ARGS( &uploadBuffer ) ) );

		UploadBuffer ub = { uploadBuffer, m_owner->GetRecordingFrameNumber() };
		m_uploadBuffers.push_back( ub );
	}

	CR_RETURN_HR( UploadInstanceData( uploadBuffer, count, instances ) );

	D3D12_BUILD_RAYTRACING_ACCELERATION_STRUCTURE_INPUTS ASInputs = {};
	ASInputs.Type = D3D12_RAYTRACING_ACCELERATION_STRUCTURE_TYPE_TOP_LEVEL;
	ASInputs.DescsLayout = D3D12_ELEMENTS_LAYOUT_ARRAY;