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FBX Import Options Reference

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While importing FBX files into Unreal Engine 4 is a relatively simple procedure, there are quite a few options available for tweaking the imported asset. This document will cover those options.

When you import content through the Content Browser using the FBX pipeline, the FBX Import Options dialog appears. The importer will automatically detect what kind of file you are attempting to import and adjust its interface accordingly.

Static Mesh Options

The options available when importing a StaticMesh using FBX are explained below.

StaticMeshImportOptions.png

Option

Description

Mesh

Skeletal Mesh

For Static Meshes: This will attempt to import the FBX file as a Skeletal Mesh. The import options will switch to handle importing the FBX file as a Skeletal Mesh.

Auto Generate Collision

This will automatically generate collision for your Static Mesh. This will not be used if custom collision is detected in the FBX file.

Subdivision Surface

Whether to subdivide the incoming FBX meshes surface.

Static Mesh LODGroup

This dropdown allows you to choose the LOD group to which the mesh will be assigned. Mesh LOD groups define default level-of-detail settings, light map resolution, and permit global overrides (e.g. reduce all SmallProp LODs by 10%). Mesh LOD group settings may be overridden per-platform / device profile. You may select an LOD group at import time and change it at any time in the Static Mesh Editor.

Vertex Color Import Option

If enabled, vertex colors on an existing mesh are replaced with the vertex colors from the FBX file. Disable this to preserve vertex colors painted within the editor using the Mesh Paint tool.

Vertex Override Color

This will be override color in the case that Vertex Color Import Option is set to Override.

Remove Degenerates

If enabled, degenerate triangles found during import will be removed. Disabling this option will keep degenerate triangles found. In general, this option should be enabled.

Build Adjacency Buffer

If true, the mesh will be optimized for PN tessellation. It is recommended to disable for larger meshes.

Build Reveresed Index Buffer

This is used to reduce the number of GPU state changes between drawcalls. This is required to optimize a mesh in mirrored transform. It will also double the index buffer size.

Generate Lightmap UVs

If enabled, the importer will generate a set of unique, non-overlapping, UVs for use with static lighting.

One Convex Hull per UCX

This option forces all UCX meshes to receive one convex hull. If disabled, then a UCX mesh could be decomposed by the engine into a series of convex hulls to get the appropriate shape.

Transform Vertex to Absolute

If true, the FBX file will use the transform, offset, and pivot for the world origin. If false, the FBX will import without any node heirarchy transform.

Bake Pivot in Vertex

If true, the pivot rotation will be applied to the mesh. The pivot of the FBX file will then be the origin of the mseh. Transform Vertex to Absolute must be set to false.

Import Mesh LODs

Creates LOD models for Unreal meshes from LODs defined in the file. Otherwise, only the base mesh from the LOD group is imported. For Skeletal Meshes, the LOD models can be skinned to the same skeleton, or a different skeleton. If the LOD model is skinned to a different skeleton, it must meet the Unreal LOD requirements, with the exception that the name of the root bones can be different since the FBX importer renames the root bones automatically.

Normal Import Method

This import option adjusts how Normals will be handled. The options are as follows:

Option

Description

Compute Normals

The engine computes normals and tangents. Smoothing group and normal info is discarded from the FBX info.

Import Normals

The normals are imported from the FBX file, tangents are computed by the engine.

Import Normals and Tangents

The normals and tangents are imported from the FBX file and nothing is computed by the engine.

Normal Generation Method

The option to choose between MikkTSpace or Built-in Normal generation method.

Combine Meshes

If enabled, all Static Meshes contained in the FBX scene are combined into a single Static Mesh.

Skeletal Mesh Options

The options available when importing a SkeletalMesh using FBX are explained below.

SkeletalMeshFBXOptions.png

Option

Description

Mesh

Skeletal Mesh

For Skeletal Meshes, disabling this will have the importer attempt to import the FBX file as a Static Mesh.

Import Mesh

Whether to import the mesh. This allows animation only imports when importing a Skeletal Mesh.

Skeleton

The Skeleton the SkeletalMesh should target. If no existing Skeleton is selected, a new one will be created from the SkeletalMesh being imported. The new Skeleton's name will be that of the SkeletalMesh with Skeleton appended.

Subdivision Surface

Whether to subdivide the incoming FBX meshes surface.

Update Skeleton Reference Pose

If enabled, this will update the Reference Pose of Skeleton Asset of the Skeletal Mesh/Animation being imported, to the reference pose in the FBX file being imported.

Use T0As Ref Pose

If enabled, the first frame (frame 0) of the animation track will be used to replace the Skeletal Mesh's reference pose.

Preserve Smoothing Group

If enabled, triangles with non-matching smoothing groups will be physically split, duplicating shared vertices.

Import Meshes in Bone Hierarchy

If enabled, meshes nested in bone hierarchies will be imported instead of being converted to bones.

Import Morph Targets

If enabled, MorphTargets will be imported from the FBX files along with the SkeletalMesh.

Keep Overlapping Vertices

If enabled, do not filter same vertices. This will keep all vertices even if they have the exact same properties.

Import Mesh LODs

If enabled, creates LOD models for Unreal meshes from LODs defined in the file. Otherwise, only the base mesh from the LOD group is imported. For skeletal meshes, the LOD models can be skinned to the same skeleton, or a different skeleton. If the LOD model is skinned to a different skeleton, it must meet the Unreal LOD requirements, with the exception that the name of the root bones can be different since the FBX importer renames the root bones automatically.

Normal Import Method

Allows for control of how Normals will be handled. The options are as follows:

Option

Description

Compute Normals

The engine computes normals and tangents. Smoothing group and normal info is discarded from the FBX info.

Import Normals

The normals are imported from the FBX file, tangents are computed by the engine.

Import Normals and Tangents

The normals and tangents are imported from the FBX file and nothing is computed by the engine.

Normal Generation Method

The option to choose between MikkTSpace or Built-in Normal generation method.

Create PhysicsAsset

If enabled, this will generate a new PhysicsAsset for the imported Skeletal Mesh. The PhysicsAsset will be composed of mostly spheres (with the exception being the root which will be a capsule/SphrL object), with the constraints being completely free on all rotational axis and completely locked on positional axis.

Select PhysicsAsset

If Create PhysicsAsset is disabled, you will be able to choose a PhysicsAsset that already exists or none to simply not have the Skeletal Mesh associated with a PhysicsAsset.

Animation Options

The options available when importing an Animation using FBX are explained below.

AnimationImportOptions.png

Option

Description

Mesh

Skeleton

The Skeleton the SkeletalMesh should target. If no existing Skeleton is selected, a new one will be created from the SkeletalMesh being imported. The new Skeleton's name will be that of the SkeletalMesh with Skeleton appended.

Animation

Import Animations

If enabled, Animations will be imported from the FBX files along with the SkeletalMesh. A name for the Animation can be entered in the text box to override the default naming.

Animation Length

Option

Description

Exported Time

This option imports animation frames based on what is defined at the time of export.

Animated Time

Will import the range of frames that have animation. Can be useful if the exported range is longer than the actual animation in the FBX file.

Set Range

This will enable the Start Frame and End Frame properties for you to define the frames of animation to import.

Import Meshes in Bone Hierarchy

If checked, the meshes nested in bone hierarchies will be imported instead of being converted to bones.

Frame Import Range

Option

Description

Min

When Set Range is used in Animation Length, this will enable you to set the start frame of the animation you wish to import.

Max

When Set Range is used in Animation Length, this will enable you to set the end frame of the animation you wish to import.

Use Default Sample Rate

If true, the default sample rate of 30 frames-per-second is used for the animation. If unchecked, the system determines the sample rate from the FBX file.

Import Custom Attribute

If enabled, import a custom attribute as a curve within the animation. Requires Import Animations to be enabled.

Set Material Curve Type

If true, tis will set the Material Curve Type for all custom attributes that exists.

Material Curve Suffixes

Specify the suffix for Material Curve Types using the custom attribute. This does not matter if Set Material Curve Type is set to true.

Remove Redundant Keys

Redundant keys will be removed when importing a custom attribute as a curve.

Delete Existing Morph Target Curves

If enabled, this deletes currently existing MorphTargets. This setting is only used when reimporting a mesh and can be set in the Skeletal Mesh Editors Reimport settings tab.

Do not import curves with 0 values

When importing a custom attribute or morph target as a curve, do not import if it doesn't have any value other than zero. This is to avoid adding extra curves to evaluate.

Preserve Local Transform

The way the engine calculates and accumulates transforms is different. We calculate the global transform and then calculate back to the local transform. In some cases, this can affect animations using 3DS Max or non-uniform scale.

Override Animation Name

The name to assign the animation. If nothing is entered here, the Naming Rules will be used. Requires Import Animations to be enabled.

Transform

The options available when importing any Static or Skeletal Mesh asset using FBX are explained below.

TransformImportOptions.png

Option

Description

Import Translation

This will enable the mesh to be moved along the XYZ axis when imported. This will be the location of the mesh when imported offset from the world origin.

Import Rotation

This will enable the mesh to be rotated along the XYZ axis when imported.

Import Uniform Scale

This will enable the mesh to be scaled uniformly when imported.

Miscellaneous

The other various options available when importing any Static or Skeletal Mesh asset using FBX are explained below.

MiscImportOptions.png

Option

Description

Convert Scene

This will convert the scene from the FBX coordinate system to use UE4's coordinate system.

Force Front XAxis

This will convert the scene from the FBX coordinate system to UE4's coordinate system with the front X axis instead of -Y axis.

Convert Scene Unit

This will convert the scene from the FBX units of measurement to UE4's unit of measure, centimeters.

Override Full Name

This will use the string "Name" field as the full name of the mesh. This option only works when the scene contains one mesh.

Material Options

The options available when importing a Material using FBX are explained below.

MaterialImportOptions.png

Option

Description

Material

Search Location

Specify where we should search for matching materials when importing:

Option

Description

Local

Search for matching material in local import folder only.

Under Parent

Search for matching material recursively from parent folder.

Under Root

Search for matching material recursively from root folder.

All Assets

Search for matching material in all asset folders.

Base Material Name

Assign a Base material to instance from when importing materials.

BaseMaterialNameSelection.png

BaseMaterialNameSelection1.png

BaseMaterialNameSelection2.png

Select your already created Material to be assigned.

After assigning a material, if it has any parameters setup you can select them via the drop-down selections.

The properties and textures have been assigned if they are setup in the Material.

Option

Description

Base Color

When there is no diffuse texture in the imported material this color property will be used to fill a constant color value instead.

Base Texture

When there is no diffuse texture in the imported FBX this texture parameter will be assgined in a created Material Instance.

Base Normal Texture

When there is no normal texture in the imported FBX this texture parameter will be assgined in a created Material Instance.

Base Emissive Color

When there is no emissive texture in the imported material this emissive color property will be used to fill a constant color value instead.

Base Emissive Texture

When there is no Emissive texture in the imported FBX this texture parameter will be assgined in a created Material Instance.

Base Specular Texture

When there is no Specular texture in the imported FBX this texture parameter will be assgined in a created Material Instance.

Import Materials

Materials are created in Unreal for each of the materials found in the FBX file. Above and beyond this, textures referenced in the FBX material will automatically be imported and if an equivalent property exists, they will be connected to those properties. Those that are not supported will be left floating free, awaiting hook up to the Unreal Material Editor.

Import Textures

If enabled, Textures referenced in the FBX file are imported into Unreal. If Import Materials is true, textures are always imported regardless of this setting.

Invert Normal Maps

If enabled and textures are being imported, normal maps values will be inverted.

Naming Rules

The table below shows how the various content types will be named when Override FullName is enabled.

The table assumes the following:

  • %1 is the name of the asset being imported, i.e. the last part of the Import Path.

  • %2 is the mesh node name in the FBX file. For SkeletalMesh, if it is composed of multiple FBX meshes, the first FBX mesh name is used as the part of FBX node name.

Content Type

Naming Rules

StaticMesh

If Override FullName is:

  • Enabled

    • If single mesh in file - Named as %1

    • If multiple meshes in file and Combine Meshes is:

      • Enabled - Named as %1

      • Disabled - Named as %1_%2

  • Disabled

    • If single mesh in file - Named as %1_%2

    • If multiple meshes in file and Combine Meshes is:

      • Enabled - Named as %1

      • Disabled - Named as %1_%2

SkeletalMesh

If Override FullName is:

  • Enabled

    • If single mesh in file - Named as %1

    • If multiple meshes in file - Named as %1_%2

  • Disabled - Named as %1_%2

AnimationSequence

If importing Animation with SkeletalMesh:

  • If animation name is entered (considered %1 in this case):

    • If single sequences in file - Named as %1

    • If multiple sequences in file - Named as %1_%2

  • If no name entered - Named as %1_%2

If importing only Animation:

  • If single sequences in file - Named as %1

  • If multiple sequences in file - Named as %1_%2

MorphTarget

Uses the names of the MorphTarget nodes in the FBX file.