This thesis would have never been written without the help from the following people: Very, very special thanks go to Dr. László Neumann for sharing his ideas with me, and helping me in all ways. This work is the result of our cooperation in the last three years, which was a wonderful time for me. I also thank Attila Neumann for all his remarks and algorithms. This thesis is a result of numerous discussions in Budapest and Vienna, and it will remind us all on this time. Very special thanks go to Prof. Werner Purgathofer who let me do my dissertation studies at his Institute. He always had time for me, and he has spent a lot of hours discussing my ideas and correcting my written work. I also thank Prof. Wilhelm Barth for acting as second reviewer of the thesis. Special thanks go to my wife and daughter whom I missed very often in these last three years.
Special thanks go to my parents and sister for their material and moral support. Finally, I would like to thank all people at the Institute of Computer Graphics, and especially Jan Přikryl for his friendly advises and help concerning LaTeX, Dieter Schmalstieg for helping me with the translation of the abstract, and Robert F. Tobler and Alexander Wilkie for rendering float images for me.