A practical model for hair mutual interactions

Abstract

Hair exhibits strong anisotropic dynamic properties which demand distinct dynamic models for single strands and hair-hair interactions. While a single strand can be modeled as a multibody open chain expressed in generalized coordinates, modeling hair-hair interactions is a more difficult problem. A dynamic model for this purpose is proposed based on a sparse set of guide strands. Long range connections among the strands are modeled as breakable static links formulated as nonreversible positional springs. Dynamic hair-to-hair collision is solved with the help of auxiliary triangle strips among nearby strands. Adaptive guide strands can be generated and removed on the fly to dynamically control the accuracy of a simulation. A high-quality dense hair model can be obtained at the end by transforming and interpolating the sparse guide strands. Fine imagery of the final dense model is rendered by considering both primary scattering and self-shadowing inside the hair volume which is modeled as being partially translucent.