Animation, has a somewhat different purpose. Whether it is a flip-book or Finding Nemo, one knows, this is not real, in the sense of reality being the sum total of actions performed in a 'real' setting.
Some films blur the distinction by combining animation with real-life settings. Who Framed Roger Rabbit, Space Jam, and more recently, Sky Captain & The World Of Tomorrow have successfully transplanted animation into the real world. Mostly, though, one is able to discern the dividing line between the real, and the unreal, mostly through a visual distinction in portrayal. Everyone knows, for example, that Roger Rabbit is not a real rabbit.
The new Tom Hanks production, The Polar Express challenges this distinction even further, by converting the actors' actions into a computer-generated landscape.
Apparently, there will be no celluloid film, until the final production stages, this takes another giant leap for film-kind, as it were.
The power of such CGI is that, for example in the Polar Express, Michael Jeter, has signed on to play the dual roles of twin brothers Smokey and Steamer, one of whom is 6'6" while the other is only 4'4". Chris Coppola, who plays the boy who doesn't believe in Santa Claus, is actually an adult. (On the reality of Santa Claus, more later...) The film is based on the children's book of the same title by Chris Van Allsburg, who also authored the book that inspired Jumanji. The book won the 1986 Caldecott Medal.
There are some notes on the design for the film as well as (possibly valid?) grouching on the part of one of the film designers here
Despite not being listed in the credits for The Polar Express for reasons that I can't imagine, I did a great job as Set designer for about six months. I have been asked not to show my work until the film comes out but will be happy to show them in a legitimate job interview
These drawings, by intention, do not look like conventional Set Design drawings. Printed hard copy on paper were only for reference. The CGI modelers did not work from these printed drawings. They took the digital AutoCAD © drawings and arranged them around a 3D cube, then computer modeled the parts within the cube, with the AutoCAD © digital data as the reference. There was no need to include dimensions, little text was required. The most important point was that a high degree of detail was required. Even screws, door knobs and hinges, and other common items had to be details to a high degree of accuracy. Any inaccuracy caused the reference drawings around the 3D cube to not line up, resulting in errors. It is a new way to design sets.
Thus Jessica Rabbit's line "I'm not bad, I'm just drawn that way" becomes a very believable defense. Courts might have a hard time determining the validity of video evidence. As per the current law,
Images stored on video or digital media, or copies of images stored on video or digital media, shall not be rendered inadmissible by the best evidence rule. Printed representations of images stored on video or digital media shall be presumed accurate representations of the images they purport to represent.
This law might need some revision once the technology described in CGI-films becomes a commodity, as it doubtless will.