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:

Translator — reads the file into a format-neutral UInterchangeBaseNodeContainer (a graph of UInterchangeBaseNode objects representing meshes, bones, textures, etc.).
Pipeline stack — a user-configured ordered list of UInterchangePipelineBase objects that transform translator nodes into factory nodes (what to create, with what settings).
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 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 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 for the full reimport workflow, programmatic API examples, and how to migrate legacy FBX import data.

Programmatic import via C++

// 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<UObject*> 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 FSoftObjectPaths 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:

// 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<UInterchangeSourceData*>& 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 — https://dev.epicgames.com/documentation/unreal-engine/interchange-framework-in-unreal-engine
Importing Assets Using Interchange — https://dev.epicgames.com/documentation/unreal-engine/importing-assets-using-interchange-in-unreal-engine
Interchange Import Reference — https://dev.epicgames.com/documentation/unreal-engine/interchange-import-reference-in-unreal-engine
Interchange Development Guides — https://dev.epicgames.com/documentation/unreal-engine/interchange-development-guides
FBX Content Pipeline — https://dev.epicgames.com/documentation/unreal-engine/fbx-content-pipeline
Working with Content — https://dev.epicgames.com/documentation/unreal-engine/working-with-content-in-unreal-engine

Deep-dive references in this skill:

references/interchange-framework.md — Interchange class map, module locations, node types, dispatcher, and factory protocol.
references/mesh-and-texture-import.md — full mesh and texture pipeline settings with source-verified property names.
references/reimport-and-import-data.md — reimport workflow, UInterchangeAssetImportData API, and legacy FBX import data migration.

Related skills: meshes-static-and-skeletal, materials-and-shaders, asset-management, audio-and-metasounds, editor-scripting-and-python.