SubMesh単位でMeshを作り直す

SubMeshExporter.cs

using System.Linq;
using UnityEditor;
using UnityEngine;

public class SubMeshExporter : ScriptableObject
{
    // Use this for initialization
    private void Start()
    {
    }

    // Update is called once per frame
    private void Update()
    {
    }

    [MenuItem("Custom/Export/ExportSubMesh(from SkinnedMeshRenderer)")]
    private static void ExportSubMeshFromSkinnedMeshRenderer()
    {
        //何も選択されていなかったら終了
        if (Selection.gameObjects.Length == 0) return;

        var gameObject = Selection.gameObjects[0];
        var skinnedMeshRenderer = gameObject.GetComponentInChildren<SkinnedMeshRenderer>();

        //選択したオブジェクトにSkinnedMeshRendererが無かったら終了
        if (skinnedMeshRenderer == null) return;

        //出力
        SubMeshExporter.ExportSubMesh(gameObject.name, skinnedMeshRenderer.sharedMesh);
    }

    [MenuItem("Custom/Export/ExportSubMesh(from MeshFilter)")]
    private static void ExportSubMeshFromMeshFilter()
    {
        //何も選択されていなかったら終了
        if (Selection.gameObjects.Length == 0) return;

        var gameObject = Selection.gameObjects[0];
        var meshFilter = gameObject.GetComponentInChildren<MeshFilter>();

        //選択したオブジェクトにMeshFilterが無かったら終了
        if (meshFilter == null) return;

        //出力
        SubMeshExporter.ExportSubMesh(gameObject.name, meshFilter.sharedMesh);
    }

    private static void ExportSubMesh(string name, Mesh mesh)
    {
        //フォルダ名の決定
        var guid = AssetDatabase.CreateFolder("Assets", name + "SubMeshes");
        var folderName = AssetDatabase.GUIDToAssetPath(guid);

        //サブメッシュの出力
        var title = "Export";
        var info = "Exporting subMesh {0}/{1} ...";
        try
        {
            for (int index = 0; index < mesh.subMeshCount; index++)
            {
                EditorUtility.DisplayProgressBar(title, string.Format(info, index + 1, mesh.subMeshCount), (float)(index + 1) / (float)mesh.subMeshCount);
                SubMeshExporter.CreateMesh(folderName, mesh, index);
            }
        }
        finally
        {
            EditorUtility.ClearProgressBar();
        }
    }

    private static void CreateMesh(string folderName, Mesh parent, int index)
    {
        //サブメッシュの三角形リスト取得
        var triangles = parent.GetTriangles(index);

        //サブメッシュの三角形リスト(同値省く)取得
        var trianglesUnique = triangles.Distinct().ToList();

        //サブメッシュの頂点位置とテクスチャ座標の切り出し
        var vertices = trianglesUnique.Select(x => parent.vertices[x]).ToArray();
        var uv = trianglesUnique.Select(x => parent.uv[x]).ToArray();
        var normals = trianglesUnique.Select(x => parent.normals[x]).ToArray();
        var tangents = trianglesUnique.Select(x => parent.tangents[x]).ToArray();

        //三角形リストの値をサブメッシュに合わせてシフト
        var triangleNewIndexes = trianglesUnique.Select((x, i) => new { OldIndex = x, NewIndex = i }).ToDictionary(x => x.OldIndex, x => x.NewIndex);
        var triangleConv = triangles.Select(x => triangleNewIndexes[x]).ToArray();

        //メッシュ作成
        var mesh = new Mesh();
        mesh.vertices = vertices;
        mesh.uv = uv;
        mesh.normals = normals;
        mesh.tangents = tangents;
        mesh.triangles = triangleConv;

        //バウンディングボリュームと法線の再計算
        mesh.RecalculateBounds();
        mesh.RecalculateNormals();

        //出力
        AssetDatabase.CreateAsset(mesh, folderName + "/submesh" + index + ".asset");
    }
}