Illuminating Global Illumination
AL: The breakthrough was making it usable for large scale movies. Global illumination has been around for a long time, but, again, the big thing here was making it faster and faster and saving time. We did at least one or two order of magnitudes to make it workable in the pipeline. Otherwise, it would've been too costly and only usable for one or two shots. And the big thing we did to improve the speed was we tweaked the computation of specular. We computed the average value of specular in all directions. We identified which direction the most important light was coming from and considered only one vector of direction for the specular instead of sampling and computing the material hundreds or thousands of times in all directions. And that did the trick in most cases.
BD: So after the initial step of baking in the point clouds for global illumination, you were able to switch to textures and simplify the specular.
AL: Correct. By moving to textures, we got excited about the possibilities.
BD: And what has been the impact on DreamWorks and the rest of the industry?
AL: The image looks less CG and much closer to real life where objects become the source of light that bounce all over the place. As far as the rest of the industry, I wouldn't know, but the Academy investigated that. But the paper that Eric and I wrote, "An Approximate Global Illumination System for Computer-Generated Films," has been widely circulated.
AL: And now lighters can do it like a real live studio where you put bounce cards around the actors to make some nice smooth lights with gradients. But the big thing as far as DreamWorks was concerned was: "Yes, we're getting a better image, but at what cost?" It was an additional cost to the production, but what we demonstrated many times was that, even though one computation was, say, 30% slower overall, the number of iterations to get an approved image, artistically-speaking, was reached much faster. That's what sold it to management. But I have to say that DreamWorks took a risk.
BD: Tell us about your role as CTO of The Bakery, where you are partnered with Erwan Maigret.
AL: As far as I'm concerned, my goal is to provide interactive tools for lighters, which will be the first time that they will have such a tool dedicated to lighting. Today you can manipulate lights and render them in an engine but separately there is no actual lighting tool, so that is where I'm very excited. And we are also developing other software solutions for the 3-D/CG industry.
Bill Desowitz is senior editor of AWN & VFXWorld.