Photosensitive trisazobenzene-based layers, after irradiation with polarized light, are employed to align the common liquid-crystal (LC) compound 4-cyano-4'-heptylbiphenyl (7CB) into predetermined patterns. Surface analysis of the trisazobenzene films indicate that ordering of the LC material is not caused by illumination-induced surface relief structures, but through "molecular mesoepitaxial" phenomena. This finding can be exploited to produce in one-step in-plane patterns of randomly oriented and ordered macroscopic LC domains by irradiation of the substrates.