The intricate dance of fabric and light

A volumetric simulation can give rise to an appearance that 'looks right' not only from far away, but also in extreme close-up. As light encounters any material, it may be reflected, scattered, or absorbed. Producing accurate and believable computer graphics renderings requires algorithms that reproduce these interactions. In the simplest systems, the models for how light reflects from a surface are far from realistic, giving all surfaces the plastic appearance that has become so commonly associated with computer graphics. Curing this problem, especially for fabrics, requires a series of conceptual leaps, leading to more complex models and requiring more complex algorithms. Once one accepts that fabric will be modeled as a collection of fibers, it is necessary to actually locate all of those fibers in space. In some cases the fibers are ordered, as in a weave or knit. In others, such as felt, they are arranged randomly. For years, our only option in graphics has been to write programs that simulate these arrangements, requiring tweaks to both the algorithms and their myriad parameters for each new fabric.