Ray Tracing Pipeline(레이트레이싱 파이프라인)

// DXC lib_6_3 이상으로 컴파일하는 HLSL 예시. RaytracingAccelerationStructure Scene : register(t0); RWTexture2D<float4> tOutput : register(u0); cbuffer CameraCB : register(b0) { row_major float4x4 inverseViewProjection; float3 cameraOrigin; float maxRayDistance; }; struct RayPayload { float4 color; }; struct LocalCB { float time; }; ConstantBuffer<LocalCB> localCB : register(b1); Texture2D<float4> localTex : register(t1); SamplerState localSampler : register(s0); [shader("raygeneration")] void raygen() { float2 uv = (float2(DispatchRaysIndex().xy) + 0.5) / float2(DispatchRaysDimensions().xy); float2 ndc = float2(uv.x * 2 - 1, 1 - uv.y * 2); // 일반 Direct3D 깊이·유한 far plane의 원근 카메라 예시. float4 world = mul(float4(ndc, 1, 1), inverseViewProjection); world.xyz /= world.w; RayDesc ray; ray.Origin = cameraOrigin; ray.Direction = normalize(world.xyz - cameraOrigin); ray.TMin = 0.001; ray.TMax = maxRayDistance; RayPayload payload = {float4(0, 0, 0, 0)}; TraceRay(Scene, RAY_FLAG_NONE, 0xff, 0, 1, 0, ray, payload); tOutput[DispatchRaysIndex().xy] = payload.color; } [shader("closesthit")] void closesthit(inout RayPayload payload, in BuiltInTriangleIntersectionAttributes attr) { // 무게중심 좌표를 임시 UV로 쓰는 데모입니다. 실제 정점 UV 보간은 별도입니다. payload.color = localTex.SampleLevel(localSampler, attr.barycentrics + float2(sin(localCB.time) * 0.1, 0), 0); } [shader("miss")] void miss(inout RayPayload payload) { payload.color = float4(0.5, 0.5, 0.5, 1); }

// 👋 Declare Handles ID3D12RootSignature* globalRootSignature = nullptr; // Global Root Signature // These can be configured prior to DispatchRays // Output radiance UAV D3D12_DESCRIPTOR_RANGE1 ranges[2]; ranges[0].BaseShaderRegister = 0; ranges[0].RangeType = D3D12_DESCRIPTOR_RANGE_TYPE_UAV; ranges[0].NumDescriptors = 1; ranges[0].RegisterSpace = 0; ranges[0].OffsetInDescriptorsFromTableStart = 0; ranges[0].Flags = D3D12_DESCRIPTOR_RANGE_FLAG_DATA_VOLATILE; // Camera Matrices CBV ranges[1].BaseShaderRegister = 0; ranges[1].RangeType = D3D12_DESCRIPTOR_RANGE_TYPE_CBV; ranges[1].NumDescriptors = 1; ranges[1].RegisterSpace = 0; ranges[1].OffsetInDescriptorsFromTableStart = D3D12_DESCRIPTOR_RANGE_OFFSET_APPEND; ranges[1].Flags = D3D12_DESCRIPTOR_RANGE_FLAG_DATA_VOLATILE | D3D12_DESCRIPTOR_RANGE_FLAG_DESCRIPTORS_VOLATILE; D3D12_ROOT_PARAMETER1 rootParameters[2]; // UAV, CBV rootParameters[0].ParameterType = D3D12_ROOT_PARAMETER_TYPE_DESCRIPTOR_TABLE; rootParameters[0].ShaderVisibility = D3D12_SHADER_VISIBILITY_ALL; rootParameters[0].DescriptorTable.NumDescriptorRanges = _countof(ranges); rootParameters[0].DescriptorTable.pDescriptorRanges = ranges; // Acceleration Structures rootParameters[1].ParameterType = D3D12_ROOT_PARAMETER_TYPE_SRV; rootParameters[1].ShaderVisibility = D3D12_SHADER_VISIBILITY_ALL; rootParameters[1].Descriptor = {}; D3D12_VERSIONED_ROOT_SIGNATURE_DESC rootSignatureDesc; rootSignatureDesc.Version = D3D_ROOT_SIGNATURE_VERSION_1_1; rootSignatureDesc.Desc_1_1.Flags = D3D12_ROOT_SIGNATURE_FLAG_NONE; rootSignatureDesc.Desc_1_1.NumParameters = _countof(rootParameters); rootSignatureDesc.Desc_1_1.pParameters = rootParameters; rootSignatureDesc.Desc_1_1.NumStaticSamplers = 0; rootSignatureDesc.Desc_1_1.pStaticSamplers = nullptr; ComPtr<ID3DBlob> signature; ComPtr<ID3DBlob> error; HRESULT hr = D3D12SerializeVersionedRootSignature( &rootSignatureDesc, signature.GetAddressOf(), error.GetAddressOf()); if (error) OutputDebugStringA(static_cast<const char*>(error->GetBufferPointer())); ThrowIfFailed(hr); ThrowIfFailed(device->CreateRootSignature(0, signature->GetBufferPointer(), signature->GetBufferSize(), IID_PPV_ARGS(&globalRootSignature))); // Root Signature 1.1 지원을 전제합니다. 미지원이면 1.0 구조/직렬화를 사용합니다.

// 👋 Declare Handles ID3D12RootSignature* localRootSignature = nullptr; // Local Root Signature // Shader tables are able to configure this root signature. D3D12_ROOT_PARAMETER1 rootParameters[2] = {}; // Viewport Misc Constant rootParameters[0].ShaderVisibility = D3D12_SHADER_VISIBILITY_ALL; rootParameters[0].ParameterType = D3D12_ROOT_PARAMETER_TYPE_32BIT_CONSTANTS; rootParameters[0].Constants = {}; rootParameters[0].Constants.ShaderRegister = 1; rootParameters[0].Constants.Num32BitValues = 4; // Texture Param SRV Table D3D12_DESCRIPTOR_RANGE1 ranges[1] = {}; ranges[0].BaseShaderRegister = 1; ranges[0].RangeType = D3D12_DESCRIPTOR_RANGE_TYPE_SRV; ranges[0].NumDescriptors = 1; ranges[0].RegisterSpace = 0; ranges[0].OffsetInDescriptorsFromTableStart = 2; ranges[0].Flags = D3D12_DESCRIPTOR_RANGE_FLAG_DATA_STATIC; rootParameters[1].ParameterType = D3D12_ROOT_PARAMETER_TYPE_DESCRIPTOR_TABLE; rootParameters[1].ShaderVisibility = D3D12_SHADER_VISIBILITY_ALL; rootParameters[1].DescriptorTable.pDescriptorRanges = &ranges[0]; rootParameters[1].DescriptorTable.NumDescriptorRanges = _countof(ranges); D3D12_STATIC_SAMPLER_DESC sampler = {}; sampler.Filter = D3D12_FILTER_MIN_MAG_MIP_POINT; sampler.AddressU = D3D12_TEXTURE_ADDRESS_MODE_BORDER; sampler.AddressV = D3D12_TEXTURE_ADDRESS_MODE_BORDER; sampler.AddressW = D3D12_TEXTURE_ADDRESS_MODE_BORDER; sampler.MipLODBias = 0; sampler.MaxAnisotropy = 1; sampler.ComparisonFunc = D3D12_COMPARISON_FUNC_NEVER; sampler.BorderColor = D3D12_STATIC_BORDER_COLOR_TRANSPARENT_BLACK; sampler.MinLOD = 0.0f; sampler.MaxLOD = D3D12_FLOAT32_MAX; sampler.ShaderRegister = 0; sampler.RegisterSpace = 0; sampler.ShaderVisibility = D3D12_SHADER_VISIBILITY_ALL; D3D12_VERSIONED_ROOT_SIGNATURE_DESC rootSignatureDesc; rootSignatureDesc.Version = D3D_ROOT_SIGNATURE_VERSION_1_1; rootSignatureDesc.Desc_1_1.Flags = D3D12_ROOT_SIGNATURE_FLAG_LOCAL_ROOT_SIGNATURE; rootSignatureDesc.Desc_1_1.NumParameters = _countof(rootParameters); rootSignatureDesc.Desc_1_1.pParameters = rootParameters; rootSignatureDesc.Desc_1_1.NumStaticSamplers = 1; rootSignatureDesc.Desc_1_1.pStaticSamplers = &sampler; ComPtr<ID3DBlob> signature; ComPtr<ID3DBlob> error; HRESULT hr = D3D12SerializeVersionedRootSignature( &rootSignatureDesc, signature.GetAddressOf(), error.GetAddressOf()); if (error) OutputDebugStringA(static_cast<const char*>(error->GetBufferPointer())); ThrowIfFailed(hr); ThrowIfFailed(device->CreateRootSignature(0, signature->GetBufferPointer(), signature->GetBufferSize(), IID_PPV_ARGS(&localRootSignature))); // Root Signature 1.1 지원을 전제합니다. 미지원이면 1.0 구조/직렬화를 사용합니다.

// Local Root: b1 root constants 4개(16 bytes) → t1 table handle(8 bytes). // shared heap의 [0]=u0, [1]=b0, [2]=t1이며 local table offset=2입니다. struct alignas(D3D12_RAYTRACING_SHADER_RECORD_BYTE_ALIGNMENT) HitRecord { unsigned char identifier[D3D12_SHADER_IDENTIFIER_SIZE_IN_BYTES]; // 32 float localConstants[4]; // time + padding D3D12_GPU_DESCRIPTOR_HANDLE heapBase; // table의 시작; offset 2 적용 }; static_assert(sizeof(HitRecord) == 64); // GetShaderIdentifier(L"MyHitGroup")의 32바이트를 identifier에 복사합니다. // RayGen/Miss에는 local root를 연결하지 않아 identifier만 담은 record를 사용합니다. // 각 table은 시작 GPU 주소를 64바이트 정렬해 할당하고 올바른 상태로 유지합니다.

// 👋 Declare handles ID3D12StateObject* pipelineState = nullptr; ID3D12StateObjectProperties* stateObjectProperties = nullptr; // 🗺️ Create the State Object Description D3D12_STATE_OBJECT_DESC stateObjectDesc = {}; stateObjectDesc.Type = D3D12_STATE_OBJECT_TYPE_RAYTRACING_PIPELINE; D3D12_STATE_SUBOBJECT subObjects[7]; stateObjectDesc.NumSubobjects = _countof(subObjects); stateObjectDesc.pSubobjects = subObjects; D3D12_EXPORT_DESC* exportDesc = nullptr; D3D12_SHADER_BYTECODE rtShaderByteCode = {rsBytecodeData.data(), rsBytecodeData.size()}; // 📚 Shader Library D3D12_DXIL_LIBRARY_DESC dxilLibraryDesc = {rtShaderByteCode, 0u, exportDesc}; subObjects[0u] = {D3D12_STATE_SUBOBJECT_TYPE_DXIL_LIBRARY, &dxilLibraryDesc}; // 📕 Active Shaders static LPCWSTR shaderNames[] = { L"MyHitGroup" }; D3D12_SUBOBJECT_TO_EXPORTS_ASSOCIATION exportAssociations = { subObjects + 4, 1u, shaderNames}; subObjects[1] = { D3D12_STATE_SUBOBJECT_TYPE_SUBOBJECT_TO_EXPORTS_ASSOCIATION, &exportAssociations}; // 💰 Payload Setup D3D12_RAYTRACING_SHADER_CONFIG shaderConfig = {}; shaderConfig.MaxPayloadSizeInBytes = 4 * sizeof(float); // float4 color shaderConfig.MaxAttributeSizeInBytes = 2 * sizeof(float); // float2 barycentrics subObjects[2] = {D3D12_STATE_SUBOBJECT_TYPE_RAYTRACING_SHADER_CONFIG, &shaderConfig}; // 📑 Hit Groups D3D12_HIT_GROUP_DESC myClosestHitGroup = { L"MyHitGroup", D3D12_HIT_GROUP_TYPE_TRIANGLES, nullptr, L"closesthit", nullptr}; subObjects[3] = {D3D12_STATE_SUBOBJECT_TYPE_HIT_GROUP, &myClosestHitGroup}; // 🚃 Root Signatures subObjects[4] = {D3D12_STATE_SUBOBJECT_TYPE_LOCAL_ROOT_SIGNATURE, &localRootSignature}; subObjects[5] = {D3D12_STATE_SUBOBJECT_TYPE_GLOBAL_ROOT_SIGNATURE, &globalRootSignature}; // 🔁 Recursion Depth D3D12_RAYTRACING_PIPELINE_CONFIG pipelineConfig = {1u}; pipelineConfig.MaxTraceRecursionDepth = 1; subObjects[6] = {D3D12_STATE_SUBOBJECT_TYPE_RAYTRACING_PIPELINE_CONFIG, &pipelineConfig}; ThrowIfFailed(device->CreateStateObject(&stateObjectDesc, IID_PPV_ARGS(&pipelineState))); ThrowIfFailed(pipelineState->QueryInterface(IID_PPV_ARGS(&stateObjectProperties)));

// API 구조 발췌: device=ID3D12Device5*, commandList=ID3D12GraphicsCommandList4*. // 업로드 완료된 VB/IB, R16_UINT 인덱스, 정점 맨 앞 float3 위치를 전제합니다. D3D12_RAYTRACING_GEOMETRY_DESC geometry = {}; geometry.Type = D3D12_RAYTRACING_GEOMETRY_TYPE_TRIANGLES; geometry.Flags = D3D12_RAYTRACING_GEOMETRY_FLAG_OPAQUE; geometry.Triangles.VertexBuffer = {vertexBuffer->GetGPUVirtualAddress(), sizeof(Vertex)}; geometry.Triangles.VertexCount = vertexCount; geometry.Triangles.VertexFormat = DXGI_FORMAT_R32G32B32_FLOAT; geometry.Triangles.IndexBuffer = indexBuffer->GetGPUVirtualAddress(); geometry.Triangles.IndexCount = indexCount; geometry.Triangles.IndexFormat = DXGI_FORMAT_R16_UINT; D3D12_BUILD_RAYTRACING_ACCELERATION_STRUCTURE_INPUTS blasInputs = {}; blasInputs.Type = D3D12_RAYTRACING_ACCELERATION_STRUCTURE_TYPE_BOTTOM_LEVEL; blasInputs.DescsLayout = D3D12_ELEMENTS_LAYOUT_ARRAY; blasInputs.NumDescs = 1; blasInputs.pGeometryDescs = &geometry; blasInputs.Flags = D3D12_RAYTRACING_ACCELERATION_STRUCTURE_BUILD_FLAG_PREFER_FAST_TRACE; D3D12_BUILD_RAYTRACING_ACCELERATION_STRUCTURE_INPUTS tlasInputs = {}; tlasInputs.Type = D3D12_RAYTRACING_ACCELERATION_STRUCTURE_TYPE_TOP_LEVEL; tlasInputs.DescsLayout = D3D12_ELEMENTS_LAYOUT_ARRAY; tlasInputs.NumDescs = 1; tlasInputs.Flags = blasInputs.Flags; D3D12_RAYTRACING_ACCELERATION_STRUCTURE_PREBUILD_INFO blasInfo = {}, tlasInfo = {}; device->GetRaytracingAccelerationStructurePrebuildInfo(&blasInputs, &blasInfo); device->GetRaytracingAccelerationStructurePrebuildInfo(&tlasInputs, &tlasInfo); // 이 지점에서 result/scratch 버퍼를 확보합니다. 아래 설명의 크기·상태를 맞춥니다. D3D12_RAYTRACING_INSTANCE_DESC instance = {}; instance.Transform[0][0] = instance.Transform[1][1] = instance.Transform[2][2] = 1.0f; instance.InstanceMask = 0xff; instance.AccelerationStructure = blasBuffer->GetGPUVirtualAddress(); // instance를 UPLOAD 버퍼에 복사하고 빌드 완료까지 유지합니다. tlasInputs.InstanceDescs = instanceBuffer->GetGPUVirtualAddress(); D3D12_BUILD_RAYTRACING_ACCELERATION_STRUCTURE_DESC blasBuild = {}, tlasBuild = {}; blasBuild.Inputs = blasInputs; blasBuild.DestAccelerationStructureData = blasBuffer->GetGPUVirtualAddress(); blasBuild.ScratchAccelerationStructureData = blasScratch->GetGPUVirtualAddress(); tlasBuild.Inputs = tlasInputs; tlasBuild.DestAccelerationStructureData = tlasBuffer->GetGPUVirtualAddress(); tlasBuild.ScratchAccelerationStructureData = tlasScratch->GetGPUVirtualAddress(); commandList->BuildRaytracingAccelerationStructure(&blasBuild, 0, nullptr); auto barrier = CD3DX12_RESOURCE_BARRIER::UAV(blasBuffer); commandList->ResourceBarrier(1, &barrier); commandList->BuildRaytracingAccelerationStructure(&tlasBuild, 0, nullptr); barrier = CD3DX12_RESOURCE_BARRIER::UAV(tlasBuffer); commandList->ResourceBarrier(1, &barrier); // BLAS/TLAS scratch를 따로 준비한 예입니다. 공유하면 재사용 Barrier도 필요합니다.

// 한 개 RayGen, 한 개 Miss, 한 개 HitGroup record를 담은 예제입니다. // 각 buffer는 사용한 record 크기만 따로 관리하며 전체 할당 크기로 stride를 정하지 않습니다. commandList->SetComputeRootSignature(globalRootSignature); // 🌎 Bind global root signature descriptor data commandList->SetDescriptorHeaps(1, &srvHeap); commandList->SetComputeRootDescriptorTable(0, srvHeap->GetGPUDescriptorHandleForHeapStart()); // 🚞 Bind TLAS commandList->SetComputeRootShaderResourceView( 1, tlasBuffer->GetGPUVirtualAddress()); // ⚡ Setup dispatch description D3D12_DISPATCH_RAYS_DESC dispatchDesc = {}; dispatchDesc.Width = width; dispatchDesc.Height = height; dispatchDesc.Depth = 1; // 🏓 Shader Binding Tables dispatchDesc.RayGenerationShaderRecord.StartAddress = rayGenShaderTable->GetGPUVirtualAddress(); dispatchDesc.RayGenerationShaderRecord.SizeInBytes = D3D12_SHADER_IDENTIFIER_SIZE_IN_BYTES; dispatchDesc.MissShaderTable.StartAddress = missShaderTable->GetGPUVirtualAddress(); dispatchDesc.MissShaderTable.SizeInBytes = D3D12_SHADER_IDENTIFIER_SIZE_IN_BYTES; dispatchDesc.MissShaderTable.StrideInBytes = dispatchDesc.MissShaderTable.SizeInBytes; dispatchDesc.HitGroupTable.StartAddress = hitShaderTable->GetGPUVirtualAddress(); dispatchDesc.HitGroupTable.SizeInBytes = sizeof(HitRecord); dispatchDesc.HitGroupTable.StrideInBytes = dispatchDesc.HitGroupTable.SizeInBytes; // 👨‍🔧 Setup Pipeline commandList->SetPipelineState1(pipelineState); // 🏁 Dispatch Rays commandList->DispatchRays(&dispatchDesc);