Fifteen years ago today, Toy Story opened in U.S. theaters, the first feature-film to be made entirely with computer-generated imagery (CGI). The current issue of ACM Queue magazine features Ed Catmul, President of Pixar Animation Studios, talking with Stanford computer graphics professor Pat Hanrahan, a former Pixar employee who worked with Catmull on Pixar’s acclaimed RenderMan rendering software, for which they share a Scientific and Engineering Oscar. Similar to the way Moore’s “Law” provided microprocessor engineers with a clear objective, Catmul says that “We believed that achieving the appearance of reality was a great technical goal—not because we were trying to emulate reality, but because doing it is so hard that it would help drive us forward.”

Here’s the full exchange from which this quote is taken:

PH When I first got interested in graphics in grad school, I heard about this quest to make a full-length computer-generated picture. At the time I was very interested in artificial intelligence, which has this idea of a Turing test and emulating the mind. I thought the idea of making a computer-generated picture was a prelim to, or at least as complicated as, modeling the human mind, because you would have to model this whole virtual world, and you would have to have people in that world—and if the virtual world and the people in it didn’t seem intelligent, then that world would not pass the Turing test and therefore wouldn’t seem plausible.

I guess I was savvy enough to think we weren’t actually going to be able to model human intelligence in my lifetime. So, one of the reasons I was interested in graphics is I thought it had a good long-term career potential. I never thought when I entered the field that by the time I died we would have made a fully computer-generated picture, but I thought it would be great fun, and eventually it would happen. Did you ever have thoughts like that?

EC Oh yes, but when I graduated my goal was not as lofty as emulating all of reality; it was to make an animated film. That was more achievable, and I thought that it would take 10 years. This was 1974, so I thought by 1984, we might be able to do it. I was off by a factor of two: it took 20 years. I remember giving talks and saying at the time, “Look at the table in front of you. Nobody has been able to make a picture that comes anywhere close to capturing the complexity of even just that table in front of you.” As we started to get close to that, it stopped being a meaningful thing to say. And, of course, now we’re way past that.

We believed that achieving the appearance of reality was a great technical goal—not because we were trying to emulate reality, but because doing it is so hard that it would help drive us forward. That is, in fact, what happened. We were trying to match the physics of the real world, and in doing that we finally reached the point where we can create convincingly realistic images. Reality was a great goal for a while. Now we have non-photorealistic rendering goals and other things like that that have supplemented it. For a number of years, animation and matching reality were very useful goals, but I never thought of them as the ultimate goal.