2nd/10_Wiki/Topics/Backend/Render State.md

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id	title	category	status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	verification_status	tags	raw_sources	last_reinforced	github_commit	tech_stack
wiki-2026-0508-render-state	Render State	10_Wiki/Topics	verified	self	GPU Render State Pipeline State Graphics State	none	A	0.9	applied	graphics gpu rendering pipeline		2026-05-10	pending	language framework hlsl/glsl vulkan/d3d12

Render State

매 한 줄

"매 GPU 명령마다 어떤 컨텍스트에서 그릴지 결정하는 파라미터 묶음". 매 blend mode, depth test, rasterizer setup, shader binding 의 collection. 매 modern Vulkan/D3D12 에서는 PSO (Pipeline State Object) 의 immutable bake — state change cost 의 minimization.

매 핵심

매 구성 요소

• Rasterizer state: cull mode, fill mode, depth bias.
• Depth-stencil state: depth test, stencil ops, write masks.
• Blend state: src/dst factors, blend op, write mask.
• Input layout: vertex attribute format.
• Shader stages: VS / PS / GS / HS / DS / CS bindings.
• Descriptor sets / root signature: resource bindings.

매 진화

• OpenGL/D3D9-11: per-state setter — glEnable(GL_DEPTH_TEST) style. Driver 의 lazy validation cost 큼.
• D3D12 / Vulkan / Metal: PSO bake at create time. Runtime change = bind 1 PSO.
• WebGPU 2025: Vulkan style PSO + 동일 abstractions.

매 응용

1. Forward / deferred 의 pass 별 PSO 분리.
2. Shadow pass 의 depth-only PSO.
3. UI overlay 의 alpha-blend PSO.

💻 패턴

Vulkan PSO 생성

VkGraphicsPipelineCreateInfo info{};
info.stageCount = 2;
info.pStages = stages;             // VS + PS
info.pVertexInputState = &vi;
info.pInputAssemblyState = &ia;
info.pRasterizationState = &rs;    // cull, fill
info.pDepthStencilState = &ds;     // test, write
info.pColorBlendState = &cb;       // alpha blend
info.layout = pipelineLayout;
info.renderPass = rp;
vkCreateGraphicsPipelines(dev, cache, 1, &info, nullptr, &pso);

State sort 의 draw call batching

std::sort(drawables.begin(), drawables.end(), [](auto& a, auto& b){
  if (a.psoHash != b.psoHash) return a.psoHash < b.psoHash;
  if (a.materialHash != b.materialHash) return a.materialHash < b.materialHash;
  return a.depth < b.depth;
});
for (auto& d : drawables) {
  if (d.psoHash != lastPso) cmd.bindPipeline(d.pso);
  if (d.materialHash != lastMat) cmd.bindDescriptorSets(...);
  cmd.draw(...);
}

Dynamic state subset

VkPipelineDynamicStateCreateInfo dyn{};
VkDynamicState ds[] = {VK_DYNAMIC_STATE_VIEWPORT, VK_DYNAMIC_STATE_SCISSOR};
dyn.dynamicStateCount = 2;
dyn.pDynamicStates = ds;
// PSO 는 viewport/scissor 없이 bake → runtime 에서 cmd.setViewport()

D3D12 root signature + PSO

CD3DX12_PIPELINE_STATE_STREAM_DESC desc;
desc.pRootSignature = rootSig;
desc.VS = {vsBlob, vsSize};
desc.PS = {psBlob, psSize};
desc.RasterizerState = CD3DX12_RASTERIZER_DESC(D3D12_DEFAULT);
desc.BlendState = CD3DX12_BLEND_DESC(D3D12_DEFAULT);
desc.DepthStencilState = CD3DX12_DEPTH_STENCIL_DESC(D3D12_DEFAULT);
device->CreateGraphicsPipelineState(&desc, IID_PPV_ARGS(&pso));

Shader hot-reload + PSO cache

auto hash = HashShaders(vs, ps) ^ HashState(rs, ds, cb);
if (auto it = cache.find(hash); it != cache.end()) return it->second;
auto pso = CreatePso(...);
cache[hash] = pso;
return pso;

Bindless descriptor + PSO 단순화

// Descriptor heap 1개 + bindless indexing → PSO 변경 거의 없음
ConstantBuffer<uint> meshIdx;
Texture2D<float4> textures[] : register(t0, space0);
float4 color = textures[NonUniformResourceIndex(materialId)].Sample(...);

매 결정 기준

상황	Approach
AAA 엔진, 수만 draw call	PSO + sort by state hash
Indie, simple 2D	Dynamic state OK, PSO 1-2개
Shader 자주 바뀜 (dev)	PSO cache + hot-reload
Mobile (tile-based)	Render pass 단위 minimization

기본값: PSO bake at level load + state-sorted draw queue.

🔗 Graph

• 부모: Graphics Pipeline · GPU
• 변형: PSO · Pipeline State Object · Root Signature
• 응용: Forward Rendering · Deferred Rendering · Shadow Mapping
• Adjacent: Vulkan · D3D12 · WebGPU

🤖 LLM 활용

언제: state-sort 알고리즘 작성, PSO cache 설계, Vulkan boilerplate 생성. 언제 X: GPU vendor 별 micro-optimization (driver 의 black-box).

❌ 안티패턴

• Per-draw PSO recreation: stutter 발생. Cache + warmup 필수.
• State leak: legacy GL 코드 의 glEnable 후 disable 누락 → 다음 frame corruption.
• Over-granular PSO: 1만 PSO → memory + driver overhead.

🧪 검증 / 중복

• Verified (Vulkan spec, D3D12 docs, GPU Gems).
• 신뢰도 A.

🕓 Changelog

날짜	변경
2026-05-08	Phase 1
2026-05-10	Manual cleanup — Render state full coverage