They used separate edge, bend, twist, and altitude springs to form an implied tetrahedron of springs between points, preventing volume collapse. Similar to these methods, we use a linear spring for stretch. Our hair model differs with the usage of two additional springs, designed to give our artists the visual look described in Section 1. We add a single spring for controlling bend, using the stably generated frame discussed above for the hair orientation. We define an additional spring to control the longitudinal stretch of curls during motion, not present in prior models.