Extract a submesh from a mesh into a new mesh instance, for Unity3D.

SubMeshExtractor.cs

public static Mesh Extract(Mesh m, int meshIndex)
{
    var vertices = m.vertices;
    var normals = m.normals;

    var newVerts = new List<Vector3>();
    var newNorms = new List<Vector3>();
    var newTris = new List<int>();
    var triangles = m.GetTriangles(meshIndex);
    for (var i = 0; i < triangles.Length; i += 3)
    {
        var A = triangles[i + 0];
        var B = triangles[i + 1];
        var C = triangles[i + 2];
        newVerts.Add(vertices[A]);
        newVerts.Add(vertices[B]);
        newVerts.Add(vertices[C]);
        newNorms.Add(normals[A]);
        newNorms.Add(normals[B]);
        newNorms.Add(normals[C]);
        newTris.Add(newTris.Count);
        newTris.Add(newTris.Count);
        newTris.Add(newTris.Count);
    }
    var mesh = new Mesh();
    mesh.indexFormat = newVerts.Count > 65536 ? IndexFormat.UInt32 : IndexFormat.UInt16;
    mesh.SetVertices(newVerts);
    mesh.SetNormals(newNorms);
    mesh.SetTriangles(newTris, 0, true);
    return mesh;
}

explains how to use this script? I couldn't make it work

public static Mesh Extract(Mesh m, int meshIndex)
{
    var vertices = m.vertices;
    var normals = m.normals;
    var uvs = m.uv;

    var newVerts = new List<Vector3>();
    var newNorms = new List<Vector3>();
    var newUVs = new List<Vector2>();
    var newTris = new List<int>();
    var triangles = m.GetTriangles(meshIndex);
    for (var i = 0; i < triangles.Length; i += 3)
    {
        var A = triangles[i + 0];
        var B = triangles[i + 1];
        var C = triangles[i + 2];
        newVerts.Add(vertices[A]);
        newVerts.Add(vertices[B]);
        newVerts.Add(vertices[C]);
        newNorms.Add(normals[A]);
        newNorms.Add(normals[B]);
        newNorms.Add(normals[C]);
        newUVs.Add(uvs[A]);
        newUVs.Add(uvs[B]);
        newUVs.Add(uvs[C]);
        newTris.Add(newTris.Count);
        newTris.Add(newTris.Count);
        newTris.Add(newTris.Count);
    }
    var mesh = new Mesh();
    mesh.indexFormat = newVerts.Count > 65536 ? IndexFormat.UInt32 : IndexFormat.UInt16;
    mesh.SetVertices(newVerts);
    mesh.SetNormals(newNorms);
    mesh.SetUVs(0, newUVs);
    mesh.SetTriangles(newTris, 0, true);

    return mesh;
}

thx for this,
upper copy paste is modified to also include UVs