Infini-D was produced by Specular and now belongs to MetaCreations. It is a professional 3d graphics and animation program aimed at broadcast professionals and amateurs alike. It is very easy to use yet very powerful. Its latest incarnation, version 4, boasts powerful features such as light rays and particles.
Although Infini-D is a sophisticated program, the basics are very easy to master, look at the tutorials to learn how to use this program.
MetaCreations have released an update for version 4. It will cost around £100 to update.
MetaCreations have released a free update for version 4. Keep an eye on their site for more details.