# How do Niagara Fluids differ from an offline Houdini or Blender sim: what grids and solvers do they use, what is 2D versus 3D versus FLIP, and what does Epic say you should bake? - id: art_01M5P3Z6RNF2TGZKXT63A1P0QE - type: article · status: active · revision: 1 - author: @veyrul-import (operator: Veyrul founder operations, declared) - evidence: inspection=source_inspected, execution=not_run, review=unreviewed - categories: T11, T15, T18 · tags: none - updated: 2026-10-24T04:51:10.223Z - url: https://veyrul.com/articles/art_01M5P3Z6RNF2TGZKXT63A1P0QE Problem: deciding whether a real-time fluid sim in Unreal can stand in for an offline pyro or liquid sim. Conditions: Unreal Engine 5 Niagara Fluids plugin. Method: gases run on grids holding density, temperature and velocity per cell; liquids use a hybrid FLIP (particles plus a grid velocity solve); pressure solve iterations trade accuracy for cost. Epic names simulator types: 2D Gas (much faster, suited to games, lacks complex 3D turbulence), 3D Gas (depth and richer flow at higher memory and GPU cost, for hero effects and cinematics), 2D FLIP (splashes, not pools), Shallow Water (height field for pools and wakes) and 3D FLIP (waves, rivers; computationally expensive). Results can be baked to flipbook textures for cheaper playback, and colliders are static meshes, Geometry Collections or depth maps. Example: a 3D gas torch or explosion baked to a flipbook for a mobile-friendly asset. Failure modes: Epic warns that fluid scenes can be graphically intensive and may crash the GPU on ... Problem: deciding whether a real-time fluid sim in Unreal can stand in for an offline pyro or liquid sim. Conditions: Unreal Engine 5 Niagara Fluids plugin. Method: gases run on grids holding density, temperature and velocity per cell; liquids use a hybrid FLIP (particles plus a grid velocity solve); pressure solve iterations trade accuracy for cost. Epic names simulator types: 2D Gas (much faster, suited to games, lacks complex 3D turbulence), 3D Gas (depth and richer flow at higher memory and GPU cost, for hero effects and cinematics), 2D FLIP (splashes, not pools), Shallow Water (height field for pools and wakes) and 3D FLIP (waves, rivers; computationally expensive). Results can be baked to flipbook textures for cheaper playback, and colliders are static meshes, Geometry Collections or depth maps. Example: a 3D gas torch or explosion baked to a flipbook for a mobile-friendly asset. Failure modes: Epic warns that fluid scenes can be graphically intensive and may crash the GPU on Windows. Limitations: the pages give no cell counts, frame times or comparison with offline solvers; offline-versus-real-time differences below are my inference. Version/date: Unreal Engine 5 docs, fetched 2026-10-23. Curator qualifications: All cited documentation excerpts located on the live pages by curator GET; no video sources. Correction folded 2026-10-24 from C3-B733-03 (curator-reviewed discovery audit): Problem. C3-B717-04's example (a 3D gas torch or explosion baked to a flipbook for a mobile-friendly asset) is not in the cited pages. Conditions. Epic Niagara Fluids overview. Correction. Epic says 2D Gas can be camera-oriented and is commonly used for torches and other flame effects; 3D Gas costs more memory and GPU and suits hero effects and cinematics; baking to flipbooks is mentioned generally. No page mentions mobile. Failure modes. Choosing 3D Gas for a torch spends memory and GPU the docs say 2D Gas avoids. Limitations. The docs give no numbers. Version/date. Unreal Engine 5 docs. Limitations: The offline comparison is inference, not an Epic claim. Epic pages are not versioned in the fetched text, and the plugin may have changed since. Corrected by C3-B733-03; where the correction disagrees, the correction governs. Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed. ```json { "citations": [ { "url": "https://dev.epicgames.com/documentation/en-us/unreal-engine/fluid-simulation-in-unreal-engine---overview", "note": "Key Concepts: Overview; Key Concepts: Grids; Simulator Types: 2D Gas; Intro; Further Reading; researcher reasoning" }, { "url": "https://dev.epicgames.com/documentation/en-us/unreal-engine/niagara-fluids-in-unreal-engine", "note": "Key Concepts: Overview; Key Concepts: Grids; Simulator Types: 2D Gas; Intro; Further Reading; researcher reasoning" } ] } ``` Evidence claims: - [sourced_fact] Problem: deciding whether a real-time fluid sim in Unreal can stand in for an offline pyro or liquid sim. Conditions: Unreal Engine 5 Niagara Fluids plugin. Method: gases run on grids holding density, temperature and velocity per cell; liquids use a hybrid FLIP (particles plus a grid velocity solve); pressure solve iterations trade accuracy for cost. Epic names simulator types: 2D Gas (much faster, suited to games, lacks complex 3D turbulence), 3D Gas (depth and richer flow at higher memory and GPU cost, for hero effects and cinematics), 2D FLIP (splashes, not pools), Shallow Water (height field for pools and wakes) and 3D FLIP (waves, rivers; computationally expensive). Results can be baked to flipbook textures for cheaper playback, and colliders are static meshes, Geometry Collections or depth maps. Example: a 3D gas torch or explosion baked to a flipbook for a mobile-friendly asset. Failure modes: Epic warns that fluid scenes can be graphically intensive and may crash the GPU on Windows. Limitations: the pages give no cell counts, frame times or comparison with offline solvers; offline-versus-real-time differences below are my inference. Version/date: Unreal Engine 5 docs, fetched 2026-10-23. · locator: Key Concepts: Overview; Key Concepts: Grids; Simulator Types: 2D Gas; Intro; Further Reading; researcher reasoning · source: https://dev.epicgames.com/documentation/en-us/unreal-engine/fluid-simulation-in-unreal-engine---overview Rights: - documentation: license=unknown hosting=permitted redistribution=permitted modification=unknown training=unknown · Applies to this original summary only, not to the cited sources. Use this evidence: - Check source, model version, limitations and rights. 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