USkinWeightModifier | Unreal Engine 5.7 Documentation

API > API/Plugins > API/Plugins/SkeletalMeshModifiers

API used to modify skin weights on a Skeletal Mesh asset.

To use:

Instantiate an instance of USkinWeightModifier

Call "SetSkeletalMesh(MyMeshAsset)", passing in the skeletal mesh you want to edit weights on

Use Get/Set weights functions, and Normalize/Prune to edit the weights as desired

When ready to commit to the asset, call CommitWeightsToSkeletalMesh() and save the asset if desired

This API can be used from C++, Blueprint or Python. Here is a sample usage of the API in Python:

import unrealcreate a weight modifier for a given skeletal mesh

skel_mesh = unreal.EditorAssetLibrary().load_asset("/Game/Characters/Wolf/Meshes/SK_Wolf") weight_modifier = unreal.SkinWeightModifier() weight_modifier.set_skeletal_mesh(skel_mesh)get weight of vertex 1234

vertex_weights = weight_modifier.get_vertex_weights(1234) print(vertex_weights)remove neck2 as an influence on this vertex

vertex_weights.pop("neck2") weight_modifier.set_vertex_weights(vertex_weights, True) print(vertex_weights)commit change to the skeletal mesh

weight_modifier.commit_weights_to_skeletal_mesh()

OUTPUT: {"head": 0.6, "neck1": 0.3, "neck2": 0.1} {"head": 0.6, "neck1": 0.3}

In Python, the per-vertex weights are stored as a dictionary mapping Bone Names to float weight values.

The "SetVertexWeights()" function expects the same data structure. You can add/remove/edit influences as needed. The SetVertexWeights() function does not normalize the weights. So you can make multiple modifications and call NormalizeVertexWeights() or NormalizeAllWeights() as desired.

The PruneVertexWeights() and EnforceMaxInfluences() functions can be used to trim small influences and clamp the total number of influences per vertex as needed.

Note that it is not required to normalize the weights by calling any of the normalize functions. Or manually before calling SetVertexWeights(). Committing the weights to the skeletal mesh will always enforce normalization.

Though it may be useful to normalize while editing.


Name	USkinWeightModifier
Type	class
Header File	/Engine/Plugins/Runtime/MeshModelingToolset/Source/SkeletalMeshModifiers/Public/SkinWeightModifier.h
Include Path	#include "SkinWeightModifier.h"

Syntax

UCLASS (MinimalAPI, BlueprintType)  
class USkinWeightModifier : public UObject

Inheritance Hierarchy

UObjectBase → UObjectBaseUtility → UObject → USkinWeightModifier

Constants

Name	Type	Remarks	Include Path
LODIndex	int32		SkinWeightModifier.h

Variables

Protected

Name	Type	Remarks	Include Path
Mesh	TObjectPtr< USkeletalMesh >	The skeletal mesh that was loaded by SetSkeletalMesh	SkinWeightModifier.h
MeshDescription	TUniquePtr< FMeshDescription >		SkinWeightModifier.h
Weights	TArray< TMap< FName, float > >	Weights stored in-memory for editing before being committed to the skeletal mesh	SkinWeightModifier.h

Functions

Public

Name	Remarks	Include Path	Unreal Specifiers
bool CommitWeightsToSkeletalMesh ()	Actually applies the weight modifications to the skeletal mesh.	SkinWeightModifier.h	BlueprintCallable Category="Mesh"
bool EnforceMaxInfluences ( const int32 MaxInfluences )	Strips out smallest influences to ensure each vertex does not have weight on more influences than MaxInfluences.	SkinWeightModifier.h	BlueprintCallable Category="Weights"
TArray< FName > GetAllBoneNames()	Get an array of all bone names in the skeletal mesh.	SkinWeightModifier.h	BlueprintCallable Category="Mesh Query"
int32 GetNumVertices()	Get the total number of vertices in the skeletal mesh.	SkinWeightModifier.h	BlueprintCallable Category="Mesh Query"
USkeletalMesh * GetSkeletalMesh()	Get a reference to the skeletal mesh that was loaded	SkinWeightModifier.h	BlueprintCallable Category="Mesh"
TMap< FName, float > GetVertexWeights ( const int32 VertexID )	Get all bone weights for a single vertex.	SkinWeightModifier.h	BlueprintCallable Category="Weights"
bool NormalizeAllWeights()	Normalize weights on all vertices in the mesh.	SkinWeightModifier.h	BlueprintCallable Category="Weights"
bool NormalizeVertexWeights ( const int32 VertexID )	Normalize weights on the specified vertex.	SkinWeightModifier.h	BlueprintCallable Category="Weights"
bool PruneAllWeights ( const float WeightThreshold )	Remove all weights below the given threshold value, on all vertices.	SkinWeightModifier.h	BlueprintCallable Category="Weights"
bool PruneVertexWeights ( const int32 VertexID, const float WeightThreshold )	Remove all weights below the given threshold value, on the given vertex.	SkinWeightModifier.h	BlueprintCallable Category="Weights"
bool SetSkeletalMesh ( USkeletalMesh* InMesh )	Call this first to load the weights for a skeletal mesh for fast editing.	SkinWeightModifier.h	BlueprintCallable Category="Mesh"
bool SetVertexWeights ( const int32 VertexID, const TMap< FName, float >& InWeights, const bool bReplaceAll )	Set bone weights for a single vertex.	SkinWeightModifier.h	BlueprintCallable Category="Weights"

Navigation