to simulate particular types of materials and really get control over the appearance of the surface. That caught the attention of Lucasfilm, which was just setting up a computer-graphics division, and it hired me. What inspired you to develop RenderMan? When you look around, you notice that most things are not just made of one material such as bronze or ivory. They are more complex than that: they have multiple materials, they are beaten up, they have scratches. We needed to give artists control over those surface appearances, so I worked on something called programmable shading that uses equations to describe how a surface looks, but also builds a framework over them to allow artists to make really complex, rich surfaces. That is at the heart of what we do with RenderMan, and over the last 16 years, every film nominated for visual effects at the Academy Awards has used it. How has your training in physics helped you? Aside from my thesis work, it also helped when we were developing RenderMan. In computer graphics, you have a virtual camera looking at a virtual world, and for special effects you want to match this with live-action footage. But for it to look convincingly real, you have to get the characteristics of your virtual camera to match those of the physical camera. That turns out to be hard for a number of reasons. One is something called "motion blur": when a physical camera takes a picture, it opens the shutter and