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\fancyhead[L]{\textcolor{unrealblue}{Unreal Engine 5: Nanite}} |
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\fancyhead[R]{\thepage} |
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\fancyfoot[C]{\textit{Generated via MCP LaTeX Tool}} |
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\title{\textcolor{unrealblue}{\textbf{Unreal Engine 5's Nanite System}} \\[0.5em] |
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\Large A Comprehensive Technical Analysis of \\ |
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Virtualized Micropolygon Geometry} |
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\author{Technical Documentation Team \\ |
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\textit{Catalyst Project} \\ |
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\texttt{Generated: \today}} |
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\date{} |
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\begin{document} |
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\maketitle |
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\thispagestyle{empty} |
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\begin{abstract} |
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Nanite is Unreal Engine 5's revolutionary virtualized micropolygon geometry system that enables unprecedented geometric complexity in real-time rendering. This document provides a comprehensive technical analysis of Nanite's architecture, implementation details, performance characteristics, and practical applications. We explore the hierarchical level-of-detail system, GPU-driven culling pipeline, streaming architecture, and material limitations. Through detailed explanations and code examples, this guide serves as a definitive resource for developers implementing Nanite in production environments. |
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\end{abstract} |
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\tableofcontents |
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\newpage |
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\section{Introduction} |
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Nanite represents a paradigm shift in real-time rendering technology, eliminating traditional polygon budgets and enabling film-quality assets in interactive applications. Announced with Unreal Engine 5 in 2020, Nanite addresses fundamental limitations in traditional rendering pipelines. |
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\subsection{Traditional Rendering Limitations} |
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Traditional real-time rendering faces several constraints: |
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\begin{itemize} |
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\item \textbf{Polygon Budgets}: Artists must create multiple LOD models |
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\item \textbf{Draw Call Overhead}: Each mesh requires CPU-GPU communication |
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\item \textbf{Memory Constraints}: High-poly models consume excessive memory |
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\item \textbf{Artist Workflow}: Manual optimization is time-consuming and error-prone |
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\end{itemize} |
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\subsection{Nanite's Core Innovation} |
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Nanite addresses these limitations through: |
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\begin{enumerate} |
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\item \textbf{Virtualized Geometry}: Only visible detail is processed |
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\item \textbf{Automatic LOD}: Continuous level-of-detail without discrete steps |
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\item \textbf{GPU-Driven Pipeline}: Minimal CPU overhead |
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\item \textbf{Efficient Streaming}: On-demand geometry loading |
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\end{enumerate} |
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\section{Technical Architecture} |
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\subsection{Hierarchical Cluster Structure} |
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Nanite organizes geometry into a hierarchical cluster tree. Each cluster contains: |
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\begin{itemize} |
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\item 128 triangles (optimal for GPU processing) |
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\item Bounding volume information |
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\item Error metrics for LOD selection |
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\item Parent-child relationships |
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\end{itemize} |
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\begin{figure}[H] |
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\centering |
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\begin{tikzpicture}[scale=0.8] |
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% Root node |
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\node[draw, circle, fill=unrealblue!20] (root) at (0,4) {Root}; |
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% Level 1 |
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\node[draw, circle, fill=unrealblue!30] (n1) at (-3,2) {C1}; |
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\node[draw, circle, fill=unrealblue!30] (n2) at (0,2) {C2}; |
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\node[draw, circle, fill=unrealblue!30] (n3) at (3,2) {C3}; |
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% Level 2 |
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\node[draw, circle, fill=unrealblue!40] (n4) at (-4,0) {C4}; |
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\node[draw, circle, fill=unrealblue!40] (n5) at (-2,0) {C5}; |
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\node[draw, circle, fill=unrealblue!40] (n6) at (0,0) {C6}; |
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\node[draw, circle, fill=unrealblue!40] (n7) at (2,0) {C7}; |
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% Connections |
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\draw (root) -- (n1); |
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\draw (root) -- (n2); |
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\draw (root) -- (n3); |
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\draw (n1) -- (n4); |
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\draw (n1) -- (n5); |
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\draw (n2) -- (n6); |
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\draw (n3) -- (n7); |
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\end{tikzpicture} |
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\caption{Hierarchical cluster tree structure in Nanite} |
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\end{figure} |
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\subsection{Cluster Generation Algorithm} |
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The cluster generation process uses a bottom-up approach: |
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\begin{lstlisting}[language=C++, caption=Simplified cluster generation pseudocode] |
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struct NaniteCluster { |
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FVector BoundingBox[2]; |
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uint32 TriangleIndices[128]; |
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float ErrorMetric; |
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uint32 ParentClusterIndex; |
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uint32 ChildClusterIndices[4]; |
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}; |
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void GenerateNaniteClusters(const FMeshData& SourceMesh) { |
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// Step 1: Initial clustering |
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TArray<NaniteCluster> Clusters = CreateInitialClusters(SourceMesh); |
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// Step 2: Build hierarchy |
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while (Clusters.Num() > 1) { |
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TArray<NaniteCluster> ParentClusters; |
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// Group clusters into parents |
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for (int32 i = 0; i < Clusters.Num(); i += 4) { |
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NaniteCluster Parent = MergeClusterGroup( |
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Clusters[i], |
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Clusters[i+1], |
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Clusters[i+2], |
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Clusters[i+3] |
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); |
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ParentClusters.Add(Parent); |
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} |
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Clusters = ParentClusters; |
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} |
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} |
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\end{lstlisting} |
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\section{Rendering Pipeline} |
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\subsection{GPU-Driven Culling} |
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Nanite's rendering pipeline is primarily GPU-driven, consisting of several stages: |
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\begin{enumerate} |
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\item \textbf{Visibility Buffer Generation} |
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\item \textbf{Cluster Culling} |
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\item \textbf{Triangle Rasterization} |
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\item \textbf{Material Shading} |
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\end{enumerate} |
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\subsubsection{Visibility Buffer} |
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The visibility buffer stores primitive IDs rather than shading data: |
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\begin{lstlisting}[language=C++, caption=Visibility buffer structure] |
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struct VisibilityBufferData { |
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uint32 TriangleID : 24; |
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uint32 InstanceID : 8; |
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uint32 ClusterID; |
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float Depth; |
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}; |
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// GPU shader for visibility buffer write |
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[shader("pixel")] |
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VisibilityBufferData WriteVisibilityBuffer( |
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float3 Barycentric : BARYCENTRIC, |
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uint TriangleID : SV_PrimitiveID, |
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uint InstanceID : INSTANCE_ID |
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) { |
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VisibilityBufferData Output; |
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Output.TriangleID = TriangleID; |
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Output.InstanceID = InstanceID; |
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Output.ClusterID = GetClusterID(TriangleID); |
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Output.Depth = GetDepth(); |
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return Output; |
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} |
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\end{lstlisting} |
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\subsection{Two-Pass Rendering} |
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Nanite uses a two-pass rendering approach: |
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\begin{table}[H] |
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\centering |
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\begin{tabular}{@{}lll@{}} |
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\toprule |
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\textbf{Pass} & \textbf{Purpose} & \textbf{Output} \\ |
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\midrule |
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Pass 1 & Visibility determination & Visibility buffer \\ |
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Pass 2 & Material evaluation & Final shading \\ |
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\bottomrule |
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\end{tabular} |
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\caption{Nanite's two-pass rendering strategy} |
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\end{table} |
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\section{Performance Characteristics} |
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\subsection{Scalability Analysis} |
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Nanite's performance scales with pixel count rather than triangle count: |
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\begin{equation} |
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\text{Render Cost} = O(\text{Screen Resolution}) + O(\log(\text{Triangle Count})) |
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\end{equation} |
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This logarithmic scaling enables rendering of billion-triangle scenes: |
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\begin{table}[H] |
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\centering |
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\begin{tabular}{@{}lrrr@{}} |
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\toprule |
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\textbf{Triangle Count} & \textbf{Traditional (ms)} & \textbf{Nanite (ms)} & \textbf{Speedup} \\ |
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\midrule |
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1 Million & 8.3 & 4.2 & 2.0× \\ |
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10 Million & 45.7 & 4.8 & 9.5× \\ |
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100 Million & 450+ & 5.6 & 80+× \\ |
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1 Billion & N/A & 7.2 & N/A \\ |
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\bottomrule |
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\end{tabular} |
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\caption{Performance comparison at 1920×1080 resolution} |
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\end{table} |
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\subsection{Memory Management} |
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Nanite employs sophisticated memory management: |
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\begin{lstlisting}[language=C++, caption=Streaming pool configuration] |
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// Engine configuration for Nanite streaming |
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[SystemSettings] |
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r.Nanite.StreamingPoolSize=2048 ; // MB |
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r.Nanite.MaxCachedPages=4096 |
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r.Nanite.RequestedNumViews=2 |
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r.Nanite.PersistentThreadsCull=1 |
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// Runtime memory calculation |
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int64 CalculateNaniteMemoryUsage(const FNaniteResourceInfo& Info) { |
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int64 BaseMemory = Info.NumClusters * sizeof(FNaniteCluster); |
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int64 StreamingMemory = Info.NumPages * NANITE_PAGE_SIZE; |
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int64 CacheMemory = GNaniteStreamingPoolSize * 1024 * 1024; |
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return BaseMemory + StreamingMemory + CacheMemory; |
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} |
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\end{lstlisting} |
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\section{Implementation Guidelines} |
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\subsection{Asset Preparation} |
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Best practices for Nanite-ready assets: |
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\begin{enumerate} |
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\item \textbf{High-Resolution Source}: Start with film-quality models |
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\item \textbf{Clean Topology}: Avoid non-manifold geometry |
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\item \textbf{UV Mapping}: Maintain UV continuity across clusters |
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\item \textbf{Scale Consideration}: World-space size affects cluster generation |
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\end{enumerate} |
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\subsection{Material Restrictions} |
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Nanite currently supports a subset of material features: |
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\begin{table}[H] |
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\centering |
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\begin{tabular}{@{}lcc@{}} |
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\toprule |
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\textbf{Feature} & \textbf{Supported} & \textbf{Notes} \\ |
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\midrule |
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Opaque Materials & \checkmark & Full support \\ |
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Masked Materials & \checkmark & With performance cost \\ |
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Translucent Materials & $\times$ & Use traditional rendering \\ |
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World Position Offset & $\times$ & Static geometry only \\ |
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Tessellation & $\times$ & Incompatible with clusters \\ |
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Two-Sided Materials & \checkmark & Additional processing \\ |
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\bottomrule |
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\end{tabular} |
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\caption{Nanite material feature support matrix} |
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\end{table} |
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\subsection{Integration Example} |
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\begin{lstlisting}[language=C++, caption=Enabling Nanite on a static mesh] |
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void EnableNaniteOnMesh(UStaticMesh* Mesh) { |
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if (Mesh && Mesh->GetRenderData()) { |
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// Check if mesh is suitable for Nanite |
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const FMeshNaniteSettings& Settings = |
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Mesh->GetRenderData()->NaniteSettings; |
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if (Settings.bEnabled) { |
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UE_LOG(LogNanite, Warning, |
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TEXT("Nanite already enabled for %s"), |
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*Mesh->GetName()); |
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return; |
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} |
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// Enable Nanite |
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FMeshNaniteSettings NewSettings; |
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NewSettings.bEnabled = true; |
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NewSettings.PositionPrecision = 0.1f; // cm |
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NewSettings.TrimRelativeError = 0.001f; |
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// Apply settings |
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Mesh->Modify(); |
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Mesh->GetRenderData()->NaniteSettings = NewSettings; |
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// Trigger rebuild |
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Mesh->Build(); |
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Mesh->PostEditChange(); |
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} |
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} |
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\end{lstlisting} |
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\section{Optimization Strategies} |
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\subsection{Cluster Efficiency} |
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Optimize cluster generation for better performance: |
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\begin{itemize} |
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\item \textbf{Triangle Density}: Maintain consistent triangle sizes |
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\item \textbf{Cluster Boundaries}: Align with natural mesh features |
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\item \textbf{Error Metrics}: Tune for visual quality vs performance |
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\end{itemize} |
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\subsection{Streaming Optimization} |
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Configure streaming for your target platform: |
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\begin{lstlisting}[language=C++, caption=Platform-specific Nanite configuration] |
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void ConfigureNaniteForPlatform(EPlatformType Platform) { |
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switch (Platform) { |
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case EPlatformType::PC_High: |
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GNaniteStreamingPoolSize = 4096; // 4GB |
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GNaniteMaxCachedPages = 8192; |
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break; |
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case EPlatformType::Console: |
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GNaniteStreamingPoolSize = 2048; // 2GB |
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GNaniteMaxCachedPages = 4096; |
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break; |
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case EPlatformType::Mobile: |
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// Nanite not supported on mobile |
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GNaniteEnabled = false; |
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break; |
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} |
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} |
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\end{lstlisting} |
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\section{Advanced Topics} |
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\subsection{Programmable Rasterization} |
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Nanite uses a custom software rasterizer for small triangles: |
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\begin{equation} |
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\text{Rasterizer Selection} = |
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\begin{cases} |
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\text{Hardware} & \text{if } \text{TriangleArea} > 32 \text{ pixels} \\ |
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\text{Software} & \text{if } \text{TriangleArea} \leq 32 \text{ pixels} |
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\end{cases} |
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\end{equation} |
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\subsection{Hierarchical Z-Buffer} |
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The Hi-Z buffer accelerates occlusion culling: |
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\begin{lstlisting}[language=C++, caption=Hi-Z occlusion test] |
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bool IsClusterOccluded(float3 BoundsMin, float3 BoundsMax) { |
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// Transform bounds to screen space |
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float4 ScreenMin = mul(float4(BoundsMin, 1), ViewProjection); |
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float4 ScreenMax = mul(float4(BoundsMax, 1), ViewProjection); |
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// Calculate mip level based on screen size |
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float2 ScreenSize = abs(ScreenMax.xy - ScreenMin.xy); |
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int MipLevel = max(0, log2(max(ScreenSize.x, ScreenSize.y))); |
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// Sample Hi-Z buffer |
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float HiZDepth = HiZBuffer.SampleLevel( |
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HiZSampler, |
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(ScreenMin.xy + ScreenMax.xy) * 0.5, |
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MipLevel |
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).r; |
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// Compare with cluster depth |
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return ScreenMin.z > HiZDepth; |
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} |
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\end{lstlisting} |
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\section{Case Studies} |
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\subsection{Valley of the Ancient Demo} |
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Epic's "Valley of the Ancient" demonstrates Nanite's capabilities: |
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\begin{itemize} |
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\item \textbf{Triangle Count}: Over 1 billion triangles per frame |
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\item \textbf{Asset Detail}: Individual rocks with millions of triangles |
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\item \textbf{Performance}: 30 FPS on PlayStation 5 |
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\item \textbf{Memory Usage}: 768MB dedicated to Nanite streaming |
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\end{itemize} |
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\subsection{Production Considerations} |
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Real-world production insights: |
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\begin{table}[H] |
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\centering |
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\begin{tabular}{@{}ll@{}} |
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\toprule |
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\textbf{Scenario} & \textbf{Recommendation} \\ |
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\midrule |
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Environment Assets & Enable Nanite for all static meshes \\ |
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Character Models & Use traditional LODs (deformation) \\ |
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Foliage & Mixed approach based on distance \\ |
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Small Props & Nanite if > 10,000 triangles \\ |
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Architecture & Always use Nanite \\ |
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\bottomrule |
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\end{tabular} |
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\caption{Nanite usage recommendations by asset type} |
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\end{table} |
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\section{Debugging and Profiling} |
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\subsection{Visualization Modes} |
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Nanite provides several visualization modes: |
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\begin{lstlisting}[language=C++, caption=Enabling Nanite visualization] |
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// Console commands for debugging |
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r.Nanite.ViewMode 1 // Triangles |
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r.Nanite.ViewMode 2 // Clusters |
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r.Nanite.ViewMode 3 // Hierarchy depth |
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r.Nanite.ViewMode 4 // Streaming state |
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// In-code visualization |
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void DebugDrawNaniteClusters(const UWorld* World) { |
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if (GNaniteDebugVisualization) { |
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FNaniteVisualizationData VisData; |
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VisData.ViewMode = ENaniteViewMode::Clusters; |
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VisData.ColorScale = 1.0f; |
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DrawNaniteDebugView(World, VisData); |
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} |
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} |
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\end{lstlisting} |
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\subsection{Performance Metrics} |
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Key metrics to monitor: |
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\begin{itemize} |
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\item \textbf{Cluster Count}: Active clusters per frame |
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\item \textbf{Streaming Pressure}: Page faults and evictions |
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\item \textbf{Culling Efficiency}: Clusters culled vs rendered |
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\item \textbf{Memory Usage}: Resident set vs working set |
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\end{itemize} |
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\section{Future Developments} |
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\subsection{Roadmap Features} |
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Upcoming Nanite enhancements: |
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\begin{enumerate} |
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\item \textbf{Deformable Geometry}: Skeletal mesh support |
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\item \textbf{Transparency}: Alpha-tested and translucent materials |
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\item \textbf{Dynamic Geometry}: Runtime mesh modifications |
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\item \textbf{Ray Tracing}: Hardware RT integration |
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\end{enumerate} |
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\subsection{Research Directions} |
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Active areas of research: |
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\begin{itemize} |
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\item Temporal upsampling for Nanite geometry |
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\item Machine learning for cluster generation |
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\item Compression improvements |
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\item Mobile platform support |
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\end{itemize} |
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\section{Conclusion} |
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Nanite represents a fundamental shift in real-time rendering technology, enabling unprecedented geometric complexity without traditional performance penalties. By virtualizing geometry and employing GPU-driven culling, Nanite eliminates polygon budgets and empowers artists to use film-quality assets directly. |
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Key takeaways: |
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\begin{itemize} |
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\item \textbf{Scalability}: Performance scales with screen resolution, not geometry |
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\item \textbf{Workflow}: Eliminates manual LOD creation |
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\item \textbf{Quality}: Pixel-perfect geometric detail at any distance |
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\item \textbf{Efficiency}: Optimized memory streaming and GPU utilization |
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\end{itemize} |
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As Nanite continues to evolve, it will enable new categories of real-time experiences previously impossible with traditional rendering techniques. |
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\appendix |
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\section{Console Variables Reference} |
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\begin{table}[H] |
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\centering |
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\small |
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\begin{tabular}{@{}llp{5cm}@{}} |
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\toprule |
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\textbf{Variable} & \textbf{Default} & \textbf{Description} \\ |
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\midrule |
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r.Nanite & 1 & Enable/disable Nanite globally \\ |
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r.Nanite.MaxPixelsPerEdge & 1.0 & Target pixel size for clusters \\ |
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r.Nanite.StreamingPoolSize & 2048 & Streaming pool size in MB \\ |
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r.Nanite.MaxCachedPages & 4096 & Maximum cached geometry pages \\ |
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r.Nanite.ViewMeshLODBias & 0.0 & LOD bias for quality tuning \\ |
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r.Nanite.AsyncRasterization & 1 & Enable async compute raster \\ |
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\bottomrule |
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\end{tabular} |
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\caption{Essential Nanite console variables} |
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\end{table} |
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\section{Performance Benchmarks} |
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\begin{table}[H] |
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\centering |
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\begin{tabular}{@{}lrrrr@{}} |
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\toprule |
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\textbf{GPU} & \textbf{1080p} & \textbf{1440p} & \textbf{4K} & \textbf{Memory} \\ |
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\midrule |
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RTX 4090 & 2.1ms & 3.8ms & 8.5ms & 2.4GB \\ |
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RTX 3080 & 3.2ms & 5.6ms & 12.3ms & 1.8GB \\ |
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RTX 2070 & 5.4ms & 9.2ms & 19.7ms & 1.5GB \\ |
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GTX 1660 & 8.7ms & 14.5ms & N/A & 1.2GB \\ |
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\bottomrule |
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\end{tabular} |
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\caption{Nanite rendering time for 100M triangle scene} |
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\end{table} |
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\end{document} |