Skeletal Mesh Merge Code

//Header File

// Fill out your copyright notice in the Description page of Project Settings.
#pragma once
#include "CoreMinimal.h"
#include "Kismet/BlueprintFunctionLibrary.h"
#include "UObject/NoExportTypes.h"
#include "MeshMergeFunctionLibrary.generated.h"
/**
* Blueprint equivalent of FSkeleMeshMergeSectionMapping
* Info to map all the sections from a single source skeletal mesh to
* a final section entry in the merged skeletal mesh.
*/
USTRUCT(BlueprintType)
struct MyProject2_API FSkelMeshMergeSectionMapping_BP
{
    GENERATED_BODY()
        /** Indices to final section entries of the merged skeletal mesh */
        UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Mesh Merge Params")
        TArray < int32 > SectionIDs;
};
/**
* Used to wrap a set of UV Transforms for one mesh.
*/
USTRUCT(BlueprintType)
struct MyProject2_API FSkelMeshMergeUVTransform
{
    GENERATED_BODY()
        /** A list of how UVs should be transformed on a given mesh, where index represents a specific UV channel. */
        UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Mesh Merge Params")
        TArray < FTransform > UVTransforms;
};
/**
* Blueprint equivalent of FSkelMeshMergeUVTransforms
* Info to map all the sections about how to transform their UVs
*/
USTRUCT(BlueprintType)
struct MyProject2_API FSkelMeshMergeUVTransformMapping
{
    GENERATED_BODY()
        /** For each UV channel on each mesh, how the UVS should be transformed. */
        UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Mesh Merge Params")
        TArray < FSkelMeshMergeUVTransform > UVTransformsPerMesh;
};
/**
* Struct containing all parameters used to perform a Skeletal Mesh merge.
*/
USTRUCT(BlueprintType)
struct MyProject2_API FSkeletalMeshMergeParams
{
    GENERATED_BODY()
        FSkeletalMeshMergeParams()
    {
        StripTopLODS = 0;
        bNeedsCpuAccess = false;
        bSkeletonBefore = false;
        Skeleton = nullptr;
    }
    // An optional array to map sections from the source meshes to merged section entries
    UPROPERTY(EditAnywhere, BlueprintReadWrite)
        TArray < FSkelMeshMergeSectionMapping_BP > MeshSectionMappings;
    // An optional array to transform the UVs in each mesh
    UPROPERTY(EditAnywhere, BlueprintReadWrite)
        TArray < FSkelMeshMergeUVTransformMapping > UVTransformsPerMesh;
    // The list of skeletal meshes to merge.
    UPROPERTY(EditAnywhere, BlueprintReadWrite)
        TArray < USkeletalMesh* > MeshesToMerge;
    // The number of high LODs to remove from input meshes
    UPROPERTY(EditAnywhere, BlueprintReadWrite)
        int32 StripTopLODS;
    // Whether or not the resulting mesh needs to be accessed by the CPU for any reason (e.g. for spawning particle effects).
    UPROPERTY(EditAnywhere, BlueprintReadWrite)
        uint32 bNeedsCpuAccess : 1;
    // Update skeleton before merge. Otherwise, update after.
    // Skeleton must also be provided.
    UPROPERTY(EditAnywhere, BlueprintReadWrite)
        uint32 bSkeletonBefore : 1;
    // Skeleton that will be used for the merged mesh.
    // Leave empty if the generated skeleton is OK.
    UPROPERTY(EditAnywhere, BlueprintReadOnly)
        class USkeleton* Skeleton;
};
/**
*
*/
UCLASS()
class MyProject2_API UMeshMergeFunctionLibrary : public UBlueprintFunctionLibrary
{
    GENERATED_BODY()
public:
    /**
    * Merges the given meshes into a single mesh.
    * @return The merged mesh (will be invalid if the merge failed).
    */
    UFUNCTION(BlueprintCallable, Category = "Mesh Merge", meta = (UnsafeDuringActorConstruction = "true"))
        static class USkeletalMesh* MergeMeshes(const FSkeletalMeshMergeParams& Params);
};





//CPP
// Fill out your copyright notice in the Description page of Project Settings.
#include "MeshMergeFunctionLibrary.h"
#include "SkeletalMeshMerge.h"
#include "Engine/SkeletalMeshSocket.h"
#include "Engine/SkeletalMesh.h"
#include "Animation/Skeleton.h"
static void ToMergeParams(const TArray<FSkelMeshMergeSectionMapping_BP>& InSectionMappings, TArray<FSkelMeshMergeSectionMapping>& OutSectionMappings)
{
    if (InSectionMappings.Num() > 0)
    {
        OutSectionMappings.AddUninitialized(InSectionMappings.Num());
        for (int32 i = 0; i < InSectionMappings.Num(); ++i)
        {
            OutSectionMappings[i].SectionIDs = InSectionMappings[i].SectionIDs;
        }
    }
};
static void ToMergeParams(const TArray<FSkelMeshMergeUVTransformMapping>& InUVTransformsPerMesh, TArray<FSkelMeshMergeUVTransforms>& OutUVTransformsPerMesh)
{
    if (InUVTransformsPerMesh.Num() > 0)
    {
        OutUVTransformsPerMesh.Empty();
        OutUVTransformsPerMesh.AddUninitialized(InUVTransformsPerMesh.Num());
        for (int32 i = 0; i < InUVTransformsPerMesh.Num(); ++i)
        {
            TArray<TArray<FTransform>>& OutUVTransforms = OutUVTransformsPerMesh[i].UVTransformsPerMesh;
            const TArray<FSkelMeshMergeUVTransform>& InUVTransforms = InUVTransformsPerMesh[i].UVTransformsPerMesh;
            if (InUVTransforms.Num() > 0)
            {
                OutUVTransforms.Empty();
                OutUVTransforms.AddUninitialized(InUVTransforms.Num());
                for (int32 j = 0; j < InUVTransforms.Num(); j++)
                {
                    OutUVTransforms[i] = InUVTransforms[i].UVTransforms;
                }
            }
        }
    }
};
USkeletalMesh* UMeshMergeFunctionLibrary::MergeMeshes(const FSkeletalMeshMergeParams& Params)
{
    TArray<USkeletalMesh*> MeshesToMergeCopy = Params.MeshesToMerge;
    MeshesToMergeCopy.RemoveAll([](USkeletalMesh* InMesh)
        {
            return InMesh == nullptr;
        });
    if (MeshesToMergeCopy.Num() <= 1)
    {
        UE_LOG(LogTemp, Warning, TEXT("Must provide multiple valid Skeletal Meshes in order to perform a merge."));
        return nullptr;
    }
    EMeshBufferAccess BufferAccess = Params.bNeedsCpuAccess ?
        EMeshBufferAccess::ForceCPUAndGPU :
        EMeshBufferAccess::Default;
    TArray<FSkelMeshMergeSectionMapping> SectionMappings;
    TArray<FSkelMeshMergeUVTransforms> UvTransforms;
    ToMergeParams(Params.MeshSectionMappings, SectionMappings);
    ToMergeParams(Params.UVTransformsPerMesh, UvTransforms);
    bool bRunDuplicateCheck = false;
    USkeletalMesh* BaseMesh = NewObject<USkeletalMesh>();
    if (Params.Skeleton && Params.bSkeletonBefore)
    {
        BaseMesh->Skeleton = Params.Skeleton;
        bRunDuplicateCheck = true;
        for (USkeletalMeshSocket* Socket : BaseMesh->GetMeshOnlySocketList())
        {
            if (Socket)
            {
                UE_LOG(LogTemp, Warning, TEXT("SkelMeshSocket: %s"), *(Socket->SocketName.ToString()));
            }
        }
        for (USkeletalMeshSocket* Socket : BaseMesh->Skeleton->Sockets)
        {
            if (Socket)
            {
                UE_LOG(LogTemp, Warning, TEXT("SkelSocket: %s"), *(Socket->SocketName.ToString()));
            }
        }
    }
    FSkeletalMeshMerge Merger(BaseMesh, MeshesToMergeCopy, SectionMappings, Params.StripTopLODS, BufferAccess, UvTransforms.GetData());
    if (!Merger.DoMerge())
    {
        UE_LOG(LogTemp, Warning, TEXT("Merge failed!"));
        return nullptr;
    }
    if (Params.Skeleton && !Params.bSkeletonBefore)
    {
        BaseMesh->Skeleton = Params.Skeleton;
    }
    if (bRunDuplicateCheck)
    {
        TArray<FName> SkelMeshSockets;
        TArray<FName> SkelSockets;
        for (USkeletalMeshSocket* Socket : BaseMesh->GetMeshOnlySocketList())
        {
            if (Socket)
            {
                SkelMeshSockets.Add(Socket->GetFName());
                UE_LOG(LogTemp, Warning, TEXT("SkelMeshSocket: %s"), *(Socket->SocketName.ToString()));
            }
        }
        for (USkeletalMeshSocket* Socket : BaseMesh->Skeleton->Sockets)
        {
            if (Socket)
            {
                SkelSockets.Add(Socket->GetFName());
                UE_LOG(LogTemp, Warning, TEXT("SkelSocket: %s"), *(Socket->SocketName.ToString()));
            }
        }
        TSet<FName> UniqueSkelMeshSockets;
        TSet<FName> UniqueSkelSockets;
        UniqueSkelMeshSockets.Append(SkelMeshSockets);
        UniqueSkelSockets.Append(SkelSockets);
        int32 Total = SkelSockets.Num() + SkelMeshSockets.Num();
        int32 UniqueTotal = UniqueSkelMeshSockets.Num() + UniqueSkelSockets.Num();
        UE_LOG(LogTemp, Warning, TEXT("SkelMeshSocketCount: %d | SkelSocketCount: %d | Combined: %d"), SkelMeshSockets.Num(), SkelSockets.Num(), Total);
        UE_LOG(LogTemp, Warning, TEXT("SkelMeshSocketCount: %d | SkelSocketCount: %d | Combined: %d"), UniqueSkelMeshSockets.Num(), UniqueSkelSockets.Num(), UniqueTotal);
        UE_LOG(LogTemp, Warning, TEXT("Found Duplicates: %s"), *((Total != UniqueTotal) ? FString("True") : FString("False")));
    }
    return BaseMesh;
}