 The success of these films, and others since, has prompted massive studio investment in effects-heavy science-fiction films.This has fueled the establishment of many independent effects houses, a tremendous degree of refinement of existing techniques, and the development of new techniques such as computer-generated imagery (CGI).It has also encouraged within the industry a greater distinction between special effects and visual effects; the latter is used to characterize post-production and optical work, while "special effects" refers more often to on-set and mechanical effects.