private MyVoxelContentCell AddCell(ref Vector3I cellCoord)
{
// Adding or creating cell can be made only once
Debug.Assert(_voxelContentCells[cellCoord.X][cellCoord.Y][cellCoord.Z] == null);
var ret = new MyVoxelContentCell();
_voxelContentCells[cellCoord.X][cellCoord.Y][cellCoord.Z] = ret;
return ret;
}