When a movie is being made, and a landscape, set or location proves too difficult or too expensive to shoot, matte artists create matte paintings to fill the frame. Traditionally artists painted scenes on glass backdrops that extended a live action scene. Today they work in Photoshop, creating digital paintings that often include 3d models. The final art is added to the movie using compositing software like AfterEffects. Matte painters are part comp artist, part fine artist, part designer and sometimes part 3d modeler. They’re close to the creative development process of the film, sometimes creating concept art for the film’s director in the beginning stages and eventually creating finished matte paintings that become part of the special effects. A whole bunch of matte painter’s portfolio sites are in the old Yahoo! directory.