// [RMS] This doesn't work because I did something stupid when
        //   making unwrap meshes. The set of triangles aren't the same. argh.
        public static DMesh3 ConvertUnwrapToUVs(RemoteControl rc, out DenseMeshUVSet UVSet, string mainName = "main")
        {
            int mainID = rc.FindObjectByName(mainName);

            rc.CompactMesh(mainID);
            DMesh3 mainMesh = ReadMeshFromMM(rc, mainID);

            Debug.Assert(mainMesh.IsCompact);

            List <int> all       = rc.ListObjects();
            List <int> unwrapIDs = new List <int>();

            foreach (int id in all)
            {
                string sName = rc.GetObjectName(id);
                if (sName.StartsWith("unwrap", StringComparison.OrdinalIgnoreCase))
                {
                    unwrapIDs.Add(id);
                }
            }
            int[] AllGroups = FaceGroupUtil.FindAllGroups(mainMesh).ToArray();


            Dictionary <int, DMesh3> Unwraps = new Dictionary <int, DMesh3>();

            foreach (int id in unwrapIDs)
            {
                DMesh3        mesh      = ReadMeshFromMM(rc, id);
                HashSet <int> subGroups = FaceGroupUtil.FindAllGroups(mesh);
                Debug.Assert(subGroups.Count == 1);
                int gid = subGroups.ToArray()[0];
                Unwraps[gid] = mesh;
            }


            UVSet = new DenseMeshUVSet();
            UVSet.TriangleUVs.resize(mainMesh.TriangleCount);
            Dictionary <Index2i, int> UVSetMap = new Dictionary <Index2i, int>();

            Dictionary <int, int> GroupCounters = new Dictionary <int, int>();

            for (int i = 0; i < AllGroups.Length; ++i)
            {
                GroupCounters[AllGroups[i]] = 0;
            }

            for (int ti = 0; ti < mainMesh.TriangleCount; ++ti)
            {
                Index3i main_tri = mainMesh.GetTriangle(ti);
                int     gid      = mainMesh.GetTriangleGroup(ti);
                int     sub_tid  = GroupCounters[gid];
                GroupCounters[gid]++;

                DMesh3  SubMesh = Unwraps[gid];
                Index3i sub_tri = SubMesh.GetTriangle(sub_tid);

                for (int j = 0; j < 3; ++j)
                {
                    int     sub_vid = sub_tri[j];
                    Index2i key     = new Index2i(gid, sub_vid);
                    int     uvset_idx;
                    if (UVSetMap.TryGetValue(key, out uvset_idx) == false)
                    {
                        Vector3d v  = SubMesh.GetVertex(sub_vid);
                        Vector2f uv = new Vector2f((float)v.x, (float)v.z);
                        uvset_idx     = UVSet.AppendUV(uv);
                        UVSetMap[key] = uvset_idx;
                    }
                    sub_tri[j] = uvset_idx;
                }

                UVSet.TriangleUVs[ti] = sub_tri;
            }

            return(mainMesh);
        }