# Ue Importing Content > Import external assets into Unreal using the Interchange framework (UInterchangeManager, UInterchangePipelineBase, UInterchangeFactoryBase, UInterchangeTranslatorBase, UInterchangeSourceData) and the legacy FBX pipeline (UFbxFactory / UnFbx::FFbxImporter). Covers the three-stage Interchange pipeline (translate → pipeline → factory), pipeline stacks, format support (FBX, glTF/GLB, OBJ, USD, images, audio), mesh and texture import settings (units/axes, normals, lightmap UVs, Nanite, sRGB/compression), skeletal mesh skeleton assignment, import asset data (UInterchangeAssetImportData / UAssetImportData), and programmatic runtime import via C++, Blueprint, and Python. Use when importing DCC content, troubleshooting wrong scale/rotation/shading after import, scripting automated batch import, customising an import pipeline, or setting up a repeatable reimport workflow. - Skill: `kevinpbuckley/ue-importing-content` (Agent Skill, multi-file: 4 files) - Install (CLI): `npx skillmds@latest add kevinpbuckley/ue-importing-content` - Raw SKILL.md: https://api.skillmd.com/api/skills/kevinpbuckley/ue-importing-content/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: DevOps & Infra - Author: kevinpbuckley (https://skillmd.com/u/kevinpbuckley) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/kevinpbuckley/ue-importing-content --- # Importing content Most "it looks wrong in Unreal" problems are import-settings problems. Know the Interchange framework's data flow, the settings that change geometry and shading, and how assets store their import provenance so reimport stays predictable. ## When to use this skill - Importing static meshes, skeletal meshes, textures, or audio from Blender, Maya, Substance Painter, or other DCC tools. - Wrong scale, rotation, flipped normals, or washed-out/over-saturated textures after import. - Setting up skeleton assignment and morph targets for character assets. - Writing automated batch import via `UInterchangeManager` in C++, Blueprint, or Python. - Customising an import pipeline (C++ subclass, Blueprint, or Python) to enforce project conventions. - Debugging why reimport does not pick up the expected source file or settings. ## Pipelines: Interchange vs legacy **Interchange** (default for FBX, glTF, GLB, OBJ, most images, audio) is the modern framework. Every import passes through three stages: 1. **Translator** — reads the file into a format-neutral `UInterchangeBaseNodeContainer` (a graph of `UInterchangeBaseNode` objects representing meshes, bones, textures, etc.). 2. **Pipeline stack** — a user-configured ordered list of `UInterchangePipelineBase` objects that transform translator nodes into *factory nodes* (what to create, with what settings). 3. **Factory** — a `UInterchangeFactoryBase` subclass that creates the final `UObject` asset (e.g. `UInterchangeStaticMeshFactory`, `UInterchangeTextureFactory`). The **legacy FBX importer** (`UFbxFactory` / `UnFbx::FFbxImporter`) handles FBX only when Interchange FBX is disabled. It has its own import dialog and options struct (`UFbxImportUI`). Both paths record source file data in a `UAssetImportData`-derived object on the asset. See [references/interchange-framework.md](references/interchange-framework.md) for a full breakdown of all Interchange classes, module locations, and the factory six-step protocol. ## Supported formats | Asset type | Interchange formats | Legacy/other | |---|---|---| | Static mesh | FBX, glTF, GLB, OBJ | FBX (legacy) | | Skeletal mesh + animation | FBX, glTF, GLB | FBX (legacy) | | Texture | PNG, TGA, JPEG, EXR, HDR, DDS, IES, PSD, BMP | — | | Audio | WAV, AIF/AIFF, FLAC, OGG, OPUS, MP3 | — | | Scene / level import | FBX, glTF, GLB, MaterialX | FBX scene legacy | FBX imports through Interchange by default in 5.8; revert to the legacy importer with the console variable `Interchange.FeatureFlags.Import.FBX 0` (and `.ToLevel 0` for scene import). ## Units, scale, and axes Unreal world units are **centimetres**. Meshes exported at the wrong scale require actor-level rescaling and break physics. - FBX: `UInterchangeFbxTranslatorSettings::bConvertSceneUnit = true` (default) converts to cm automatically. Prefer exporting at 1 unit = 1 cm from the DCC. - Axis: Unreal is **left-handed, Z-up**. `bConvertScene = true` (default) remaps Y/Z from right-handed sources. `EInterchangeCoordinateSystemPolicy` controls the exact strategy: `MatchUpForwardAxes` (default), `MatchUpAxis`, or `KeepXYZAxes`. - Apply all transforms / freeze rotation in the DCC before export; baked-in offsets appear as permanent root-bone offsets on skeletal meshes. ## Mesh import settings that matter These map to properties on `UInterchangeGenericMeshPipeline` (Interchange) or `UFbxStaticMeshImportData` / `UFbxSkeletalMeshImportData` (legacy): | Setting | Effect | Common mistake | |---|---|---| | **Combine Static Meshes** (`CombineStaticMeshesBehavior`) | Merges all meshes in the file into one SM (`All`/`VisibleOnly`/`DoNotCombine`) | Leave on `DoNotCombine` when file has multiple independent assets | | **Normals / Tangents** (`Build` > Recompute Normals/Tangents) | Trust DCC normals vs let UE recompute | Mismatch causes shading seams at UV splits | | **Generate Lightmap UVs** (`bGenerateLightmapUVs`) | Auto-generates a second UV channel for Lightmass | Needed for baked lighting; off for pure Lumen | | **Build Nanite** (`bBuildNanite`) | Enables Nanite on static meshes | On by default in 5.8 Interchange; disable for low-poly props | | **LOD Group** | Assigns Epic's LOD reduction presets | Pick `SmallProp`, `LargeDetail`, etc. to match use case | | **Collision** (`bCollision`) | Imports/generates simple collision | Prefix meshes with `UCX_`, `UBX_`, `USP_`, `UCP_` for custom shapes | Skeletal mesh–specific: - **Skeleton** (`CommonSkeletalMeshesAndAnimationsProperties`) — reuse one skeleton asset across compatible meshes so all animations are shareable. - **Import Content Type** — `GeometryAndSkinningWeights`, `GeometryOnly`, or `SkinningWeightsOnly`. Split imports can be parallelised for large character updates. - **Import Morph Targets** — imports blend shapes from FBX/glTF morph target data. - **Create Physics Asset** — auto-generates a `UPhysicsAsset` if none exists. See [references/mesh-and-texture-import.md](references/mesh-and-texture-import.md) for the full mesh and texture settings reference with source-verified property names. ## Texture import settings that matter | Setting | Correct value | Consequence of wrong value | |---|---|---| | **sRGB** | ON for color/albedo; OFF for data maps | Data maps (normal, roughness, metallic, masks) with sRGB ON look wrong in lighting | | **Compression** | `Default` (BC1/BC3) for color; `Normalmap` (BC5) for normals; `Masks`; `HDR` for EXR/HDR | Wrong compression costs memory or quality | | **Flip Normal Map Green Channel** | Match DCC convention (on for Maya/DirectX, off for Blender/OpenGL-style) | Specular highlight in wrong direction | | **Detect Normal Map Texture** | ON (default) | Leave on; it sets sRGB=false and compression=Normalmap automatically | | **UDIM** (`bImportUDIMs`) | ON for assets with UDIM naming (`_1001`, `_1002`, …) | Multi-tile textures import as separate unrelated assets | Texture compression and LOD group are stored on the `UTexture2D` asset; change them in the Texture Editor or set them in a custom pipeline's `ExecutePostFactoryPipeline`. ## Import asset data and reimport Every imported asset stores provenance in a `UAssetImportData`-derived subobject: - **Interchange path**: `UInterchangeAssetImportData` (subclass of `UAssetImportData`) stores the source file path, the translator settings, the pipeline list, and the node container snapshot. Accessible with `UInterchangeAssetImportData::GetFromObject(Asset)`. - **Legacy FBX path**: `UFbxAssetImportData` / `UFbxStaticMeshImportData` (subclasses of `UAssetImportData`). - The base class `UAssetImportData` stores source file path, timestamp, and MD5 hash in `FAssetImportInfo::FSourceFile` entries — enabling reimport to detect stale files. Reimport replays the same pipeline stack and settings stored in the import data. Call `UInterchangeManager::ReimportAsset` / `ReimportAssetAsync` programmatically; the manager reads `UInterchangeAssetImportData` to resolve the original source file. See [references/reimport-and-import-data.md](references/reimport-and-import-data.md) for the full reimport workflow, programmatic API examples, and how to migrate legacy FBX import data. ## Programmatic import via C++ ```cpp // Create a source data handle pointing to a file on disk. UInterchangeSourceData* Src = UInterchangeManager::CreateSourceData(TEXT("D:/Art/Rock.glb")); // Build import parameters. FImportAssetParameters Params; Params.bIsAutomated = true; // suppress dialogs // Synchronous import (editor-only; blocking on game thread). UInterchangeManager& Mgr = UInterchangeManager::GetInterchangeManager(); TArray Imported; Mgr.ImportAsset(TEXT("/Game/Meshes"), Src, Params, Imported); // Async import with a completion callback. UE::Interchange::FAssetImportResultRef Result = Mgr.ImportAssetAsync(TEXT("/Game/Meshes"), Src, Params); Result->OnDone([](UE::Interchange::FImportResult& R) { for (UObject* Obj : R.GetImportedObjects()) { UE_LOG(LogTemp, Log, TEXT("Imported: %s"), *Obj->GetName()); } }); ``` Key API points: - `UInterchangeManager` is a singleton; use `GetInterchangeManager()` (native) or `GetInterchangeManagerScripted()` (Blueprint/Python callable). - `FImportAssetParameters::OverridePipelines` accepts a list of `FSoftObjectPath`s to bypass the project-default pipeline stack with a custom one. - `FImportAssetParameters::bIsAutomated = true` prevents any modal dialog from opening — essential for unattended batch import. - For runtime import in a cooked build, the `Interchange` content folder must be added to **Project Settings > Packaging > Additional Asset Directories to Cook**. ## Writing a custom pipeline in C++ Subclass `UInterchangePipelineBase` and override the virtual pipeline hooks: ```cpp // MyImportPipeline.h #pragma once #include "InterchangePipelineBase.h" #include "MyImportPipeline.generated.h" UCLASS(BlueprintType, editinlinenew) class MYMODULE_API UMyImportPipeline : public UInterchangePipelineBase { GENERATED_BODY() /** Shown in the Interchange dialog; locked during reimport. */ UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "My Settings", meta = (ReimportRestrict = "true")) bool bEnforceNamingConvention = true; protected: virtual void ExecutePipeline( UInterchangeBaseNodeContainer* NodeContainer, const TArray& SourceDatas, const FString& ContentBasePath) override; virtual void ExecutePostFactoryPipeline( const UInterchangeBaseNodeContainer* NodeContainer, const FString& FactoryNodeKey, UObject* CreatedAsset, bool bIsAReimport) override; }; ``` - `ExecutePipeline` fires after translation; add/modify factory nodes to control what assets get created and with what settings. - `ExecutePostFactoryPipeline` fires after the factory creates the asset but before `PostEditChange`; modify the live `UObject` here. - `ExecutePostImportPipeline` fires after `PostEditChange` and async build; use for post-build fixups (e.g. setting socket transforms that depend on render data). - Mark properties `ReimportRestrict = "true"` to prevent them being changed during reimport. Register the pipeline asset in your project's pipeline stack via **Project Settings > Engine > Interchange** or pass it via `FImportAssetParameters::OverridePipelines`. ## Naming conventions `SM_` static mesh · `SK_` skeletal mesh · `SKEL_` skeleton · `T_` texture · `M_` material · `MI_` material instance · `A_` / `S_` sound · `BP_` Blueprint · `DA_` data asset · `DT_` data table. Consistent prefixes make content browsable and scriptable. ## Gotchas - **Wrong scale** — almost always DCC export units or `bConvertSceneUnit` mismatch; fix at source, not by scaling actors. A 100× scale error is common when Blender units = meters. - **sRGB on for normal/data maps** → wrong lighting; `bDetectNormalMapTexture` catches it for textures whose names follow conventions, but verify manually. - **Reimporting against a different skeleton** — animations bound to the old skeleton break; keep one skeleton per character rig. - **CombineStaticMeshesBehavior** set to combine for files with separate per-material meshes → single SM with multiple material slots instead of independent assets. - **Missing lightmap UVs with baked lighting** → splotchy shadows; enable `bGenerateLightmapUVs` or author a dedicated UV channel. - **Interchange handles FBX by default in 5.8** — if a project depends on legacy FBX importer behavior, disable `Interchange.FeatureFlags.Import.FBX` intentionally. - **Runtime import without cooking the Interchange folder** → pipelines missing at runtime; add `/Engine/Plugins/Interchange/Runtime/Content` to packaging cook paths. - **Large batches saturate the task graph** — use `ImportAssetAsync` and throttle concurrent calls; `UInterchangeManager::IsImporting()` checks whether an import is in flight. ## Version notes - Interchange is the default importer for glTF/GLB and most textures since UE 5.0; it has expanded each release. In 5.8 FBX imports through Interchange by default; the legacy importer remains available by disabling `Interchange.FeatureFlags.Import.FBX`. - `UInterchangeAssetImportData` replaces per-format import data classes for Interchange- handled assets; legacy paths still produce `UFbxAssetImportData` etc. - `UInterchangeFbxTranslatorSettings::bUseUfbxParser` (still experimental in 5.8) enables the ufbx SDK instead of the Autodesk FBX SDK — useful for open-source builds. ## References & source material Engine source (UE 5.8): Core Interchange (under `Engine/Source/Runtime/Interchange/`): - `Engine/Public/InterchangeManager.h` — `UInterchangeManager` singleton, `ImportAsset`:648, `ImportAssetAsync`:682, `ReimportAsset`:711, `CreateSourceData`:804, `CanReimport`:634, `GetTranslatorForSourceData`:835, `FImportAssetParameters`:407. - `Core/Public/InterchangeTranslatorBase.h` — `UInterchangeTranslatorBase`:63, `Translate()`:98, `GetSupportedFormats()`:90, `CanImportSourceData()`:70. - `Core/Public/InterchangePipelineBase.h` — `UInterchangePipelineBase`:219, `ExecutePipeline`:603, `ExecutePostFactoryPipeline`:612, `ExecutePostImportPipeline`:620, `EInterchangePipelineContext`:46, `EInterchangePipelineTask`:37. - `Core/Public/InterchangeFactoryBase.h` — `UInterchangeFactoryBase`:70, `BeginImportAsset_GameThread`:150, `ImportAsset_Async`:178, `EndImportAsset_GameThread`:194, `SetupObject_GameThread`:289, `BuildObject_GameThread`:302, `FinalizeObject_GameThread`:318. - `Core/Public/InterchangeSourceData.h` — `UInterchangeSourceData`:22, `GetFilename()`, `SetFilename()`, `GetFileContentHash()`. - `Engine/Public/InterchangeAssetImportData.h` — `UInterchangeAssetImportData`:20, `GetFromObject()`:118, `GetNodeContainer()`:142, `GetPipelines()`:151, `GetTranslatorSettings()`:167. - `Engine/Public/InterchangeProjectSettings.h` — `FInterchangePipelineStack`:31. Interchange plugin (under `Engine/Plugins/Interchange/Runtime/Source/`): - `Import/Public/Fbx/InterchangeFbxTranslator.h` — `UInterchangeFbxTranslator`:81, `UInterchangeFbxTranslatorSettings`:34 (`bConvertScene`, `bConvertSceneUnit`, `bForceFrontXAxis`, `EInterchangeCoordinateSystemPolicy`). - `Import/Public/Gltf/InterchangeGltfTranslator.h` — `UInterchangeGLTFTranslator`:26. - `Pipelines/Public/InterchangeGenericMeshPipeline.h` — `UInterchangeGenericMeshPipeline`:53 (`bImportStaticMeshes`, `CombineStaticMeshesBehavior`, `bBuildNanite`, `bGenerateLightmapUVs`, `bCollision`, `bImportSkeletalMeshes`, `SkeletalMeshImportContentType`). - `Pipelines/Public/InterchangeGenericTexturePipeline.h` — `UInterchangeGenericTexturePipeline`:19 (`bImportTextures`, `bDetectNormalMapTexture`, `bFlipNormalMapGreenChannel`, `bImportUDIMs`). - `Pipelines/Public/InterchangeGenericAnimationPipeline.h` — animation settings. - `FactoryNodes/Public/InterchangeStaticMeshFactoryNode.h` — `UInterchangeStaticMeshFactoryNode`. - `FactoryNodes/Public/InterchangeSkeletalMeshFactoryNode.h` — `UInterchangeSkeletalMeshFactoryNode`. - `FactoryNodes/Public/InterchangeTextureFactoryNode.h` — `UInterchangeTextureFactoryNode`. Legacy FBX (under `Engine/Source/Editor/UnrealEd/Classes/Factories/`): - `Factory.h` — `UFactory`:46 (base class for all legacy import factories). - `FbxImportUI.h` — `UFbxImportUI`, `EFBXImportType`. - `FbxStaticMeshImportData.h`, `FbxSkeletalMeshImportData.h`, `FbxTextureImportData.h` — per-type legacy settings structs. Runtime Engine: - `Engine/Classes/EditorFramework/AssetImportData.h` — `UAssetImportData`:71, `FAssetImportInfo::FSourceFile` (path, timestamp, MD5 hash). Official docs (UE 5.8, all fetched and verified): - Interchange Framework — - Importing Assets Using Interchange — - Interchange Import Reference — - Interchange Development Guides — - FBX Content Pipeline — - Working with Content — Deep-dive references in this skill: - [references/interchange-framework.md](references/interchange-framework.md) — Interchange class map, module locations, node types, dispatcher, and factory protocol. - [references/mesh-and-texture-import.md](references/mesh-and-texture-import.md) — full mesh and texture pipeline settings with source-verified property names. - [references/reimport-and-import-data.md](references/reimport-and-import-data.md) — reimport workflow, `UInterchangeAssetImportData` API, and legacy FBX import data migration. Related skills: `ue-meshes-static-and-skeletal`, `ue-materials-and-shaders`, `ue-asset-management`, `ue-audio-and-metasounds`, `ue-editor-scripting-and-python`.