Virtual worlds are frequently used in the entertainment industry (video games, movies) to provide users with a unique and extraordinary experience. Among the fundamental elements that contribute to this experience, the quality of the setting, decorations, props, together with the dramatic character and extent of the domain is central. To obtain a vast and highly detailed virtual landscape, the entertainment industry is used to resorting massively to artists. This method is man-power intensive, costly, and has definite limitations. In parallel, an increasing number of Geographic Information Systems datasets (terrains, aerial photography, canopy height models) are now publicly accessible, which is made achievable by modern digitizing systems becoming standards. The goal of the Ph.D. thesis is to propose high-level techniques to assist artists in authoring and creating virtual worlds. This help will be provided as high-level tools that will support users in their tasks, without introducing any trade-off in the creative pipeline. This means that such tools should not hinder creativity, and particularly, artists should have access to different levels of control.