[1] TU Darmstadt, Dept. of Computer Science, Fraunhoferstr. 5, 64283 Darmstadt, Germany
[2] Fraunhofer Institute for Computer Graphics Research (IGD), Fraunhoferstr. 5, 64283 Darmstadt, Germany
[3] MPI Informatik, Campus E1 4, 66123 Saarbrücken, Germany
[4] ETH Zurich, Photogrammetry and Remote Sensing, Wolfgang-Pauli-Str. 15, 8093 Zurich, Switzerland