https://mr0ptimist.github.io/tags/ue5/Recent content in UE5 on MrOptimistHugozh-cnTue, 21 Apr 2026 00:00:00 +0000https://mr0ptimist.github.io/posts/ue5-nanite-%E4%B8%8E%E4%BC%A0%E7%BB%9F%E6%B8%B2%E6%9F%93%E7%AE%A1%E7%BA%BF%E7%9A%84%E6%B7%B1%E5%BA%A6%E6%BA%90%E7%A0%81%E5%AF%B9%E6%AF%94/Tue, 21 Apr 2026 00:00:00 +0000https://mr0ptimist.github.io/posts/ue5-nanite-%E4%B8%8E%E4%BC%A0%E7%BB%9F%E6%B8%B2%E6%9F%93%E7%AE%A1%E7%BA%BF%E7%9A%84%E6%B7%B1%E5%BA%A6%E6%BA%90%E7%A0%81%E5%AF%B9%E6%AF%94/<blockquote> <p>本文基于 UE 5.4/5.5 引擎源码，从源码层面深入对比 Nanite 渲染管线与传统网格渲染管线的差异。所有代码引用均标注了引擎内的原始路径。</p> </blockquote> <hr> <h2 id="1-宏观架构概览">1. 宏观架构概览</h2> <p>传统渲染管线和 Nanite 管线的最根本区别在于：<strong>几何处理的主导权从 CPU 转移到了 GPU</strong>，并且<strong>材质着色从 Pixel Shader 迁移到了 Compute Shader</strong>。</p> <table> <thead> <tr> <th>维度</th> <th>传统渲染 (Traditional)</th> <th>Nanite</th> </tr> </thead> <tbody> <tr> <td><strong>几何裁剪</strong></td> <td>CPU-driven Frustum/Occlusion Culling</td> <td>GPU-driven Cluster Culling + Two-Pass Occlusion</td> </tr> <tr> <td><strong>LOD</strong></td> <td>离散 LOD (StaticMesh LOD0~N)</td> <td>连续 LOD (Cluster Hierarchy, Runtime Streaming)</td> </tr> <tr> <td><strong>光栅化</strong></td> <td>硬件光栅化 (Fixed Function RS)</td> <td>软件光栅化 (Compute) + 硬件光栅化 (Mesh/Prim Shader)</td> </tr> <tr> <td><strong>中间表示</strong></td> <td>无 (直接写 GBuffer/FrameBuffer)</td> <td>Visibility Buffer (VisBuffer64)</td> </tr> <tr> <td><strong>材质着色</strong></td> <td>Pixel Shader (<code>BasePassPixelShader.usf</code>)</td> <td>Compute Shader (<code>ComputeShaderOutputCommon.ush</code>)</td> </tr> <tr> <td><strong>GBuffer 输出</strong></td> <td><code>SV_Target</code> MRT</td> <td>UAV (<code>ComputeShadingOutputs.OutTargetN</code>)</td> </tr> <tr> <td><strong>DrawCall</strong></td> <td><code>FMeshDrawCommand</code> (CPU 组装)</td> <td>Indirect Dispatch (GPU 驱动)</td> </tr> </tbody> </table> <hr> <h2 id="2-渲染入口与调度">2. 渲染入口与调度</h2> <h3 id="21-传统渲染的入口">2.1 传统渲染的入口</h3> <p>传统渲染的顶层调度在 <code>FDeferredShadingSceneRenderer::Render()</code> 中，通过 <code>RenderBasePass()</code> 等函数发起。每个 <code>FPrimitiveSceneProxy</code> 会在 <code>FMeshPassProcessor</code> 中被转换为 <code>FMeshDrawCommand</code>，最终由 <code>FParallelMeshDrawCommandPass</code> 提交到 RHI。</p>