We present a method for efficient synthesis of photorealistic freeform knitwear. Our approach is motivated by the observation that a single cross-section of yam can serve as the basic primitive for modeling entire articles of knitwear. This primitive, called the lumislice, describes radiance from a yarn cross-section based on fine-level interactions - such as occlusion, shadowing, and multiple scattering - among yam fibers. By representing yam as a sequence of identical but rotated cross-sections, the lumislice can effectively propagate local microstructure over arbitrary stitch patterns and knitwear shapes. This framework accommodates varying levels of detail and capitalizes on hardware-assisted transparency blending. To further enhance realism, a technique for generating soft shadows from yam is also introduced.