Rant: The Problems with CGI
io9 recently ran an article entitled, "Does CGI Ruin Movies?" that really got me "grinding my gears", as Peter Griffin would say. I wouldn't say that CGI necessarily ruins movies, but even 16 years after Jurassic Park, there are still some serious flaws in the technology that movie makers either don't realize or don't address.
The above article claims that CGI has a tendency to turn movies into nothing more than special effects spectacles, more so than movies from the old days with practical effects. I disagree; there were plenty of crappy visual effects spectacles back then, and the ratio of truly great special effecty movies to crappy special effecty movies is probably very much the same as it is today. It's difficult to say that a movie like Big Trouble in Little China, despite the fact that it's entertaining, is anything more than a shallow visual spectacle.
io9 also says that CGI movies lack an element of chaos. In other words, reality has a certain degree of randomness that is either difficult or impossible to create in the computer. I agree with that; CGI grass can't move like real grass because each blade of real grass is an individual with variations in size, color, flexibility, etc. that would be impossible for CGI to replicate. While this is an inherent flaw, I believe the primary problems with CGI are as follows:
Since filmmakers don't have to worry about physically building anything with CGI, they can go hog wild with character and environment designs. But because of this, the designs are often inherently unrealistic. How many movies have those spindly aliens/robots that can't possibly exist in reality without snapping like twigs? The Star Wars prequels are lousy with them, and it looks like the Avatar Thundersmurfs follow suit. And the robots in the Transformers movies are so insanely complicated that, no matter how cool they look, they have a feel of impossibility to them.
That goes for environment designs, too. The floating islands in Avatar are perfect examples of something that probably looked cool on paper but is so totally unrealistic that when you see it on screen it takes you out of the moment.
Since the animators can control everything about a CGI element, they tend to animate in a manner inconsistent with reality. This was true back in the days of the Star Wars prequels as every inch of Boss Nass' face moves when he talks, and it's still true today with movies like Transformers. When Bumblebee transforms, it's like every little part folds into itself and back again. And if you compare a shot of Bumblebee as a robot with the car he's supposed to transform into, you can see that the parts of the robot and the parts of the car can't possibly reconcile each other. There's no way for that robot to turn into that car, so the animators flub the transformation process... further removing reality from the special effect.
Blu-rays have the most resolution of any form of home entertainment at 1080p, but since the resolution of real 35mm film exceeds even that, some quality is lost in the transition. Something similar might happen with creating CGI effects for a movie. Since you're taking film elements and transferring them into the computer, I think there's a image resolution bottleneck in which the film elements are compressed. Digital film cameras might have a lower resolution than 35mm film cameras too, which might explain why a movie shot entirely with digital cameras like Revenge of the Sith looks cartoony compared with a movie shot on "real" film, like Wrath of Khan.
I'm not entirely sure about that because I can't find reliable numbers on the different resolutions. But it looks like a plausible explanation to me.
Overall, CGI effects aren't inherently bad and the technology does open up a lot of possibilities for storytelling that movie makers never had in the old days. But it's not a catch-all, and those movie makers who rely too much on CGI are missing out on the possibilities for creating a truly engaging and engrossing special effects experience.
Update 12/11/2009: If you're having trouble seeing the grotesquely over-designed Optimus Prime in the above image, here's a copy of the pic with some explanatory labels.