Visualizing Your Story
At this point, in addition to writing, you'll need to be visualizing. Animation is a very visual medium, so you will absolutely need to see how your film looks on every shot. Even if you draw in stick figures, sketching out your ideas in storyboard form will help you understand exactly how gags and situations in your film will be staged.
While sketching storyboard panels can be very quick for some people, others have problems with drawing. Drawing 3D characters might be less accurate because the drawings might not be true to the actual characters. If your characters are already built, you can visualize the story another way, without drawing. Simply pose the characters in your 3D application, and render stills to use as the storyboard. No scanning is required; the images are true to the actual characters, and the 3D scene files can be saved and used later as layouts for animation.