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.
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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.
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):
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.
// 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)
classMYMODULE_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:
virtualvoidExecutePipeline(
UInterchangeBaseNodeContainer* NodeContainer,
const TArray<UInterchangeSourceData*>& SourceDatas,
const FString& ContentBasePath)override;
virtualvoidExecutePostFactoryPipeline(
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.
