Games often have cinematics, short movie clips, conveying the story.
During the production of SACRED (2004) I redesigned the intro by adding shots and refining the soundtrack, edited short videos for the chapters and wrote, supervised the production and edited the extro.
Usually I start with skribbling storyboards in addition to a written screenplay. If an external animation company it proved a prudent course of action to provide not only a screenplay written in a "table form" with separat columns for shot content, sound effects, technology and of course shot number, but also to provide an animated storyboard as well.
The images you see here display my first approach to illustrate the 3D-artists, what it was I had in mind. The images weren't considered to be beautiful, but a "hot and dirty" approach to show what I meant.