During most of July and August there is a direct bus from Lucerne to Rovinj. The bus travel distance is about 760 km which equals a bus travel time of about 13 hours. The bus departures Lucerne on Friday and arrives in Rovinj on Saturdays, the returning bus departure from Rovinj on Saturdays, so you can enjoy a full weeks holiday in Rovinj. If you wish to travel from Lucerne to Rovinj in periods where this bus does not operate, you can do that via the Lucerne to Rijeka line which operates several times a week year around.