Collaborative Research: HCC: Small: Understanding Human Hair With Type 4 Simulation

了解人类头发的机制在视觉媒体中有着广泛的应用，并且对于忠实地描绘虚拟人至关重要，因为在面部之后，头发是我们在建立一个人的身份时所关注的下一个特征。 然而，几乎所有现有的研究都集中在对直发或卷发的描述上，在步行者的头发分型系统中，直发或卷发跨越了1型到3型，而4型头发，也被称为非洲纹理或扭结头发，几乎没有受到关注。 这种知识差距是不幸的，因为美国数百万人和全球10亿人的自然发生的头发类型是4型;因此，在数字媒体中表示和模拟虚拟的4型头发是困难的，因为现有的算法没有考虑到其特定的计算挑战。 更广泛地说，如果没有对4型的全面调查，就不可能全面了解人类头发。 该项目将通过为4型头发开发新的机械模型和有效的计算方法来解决这些缺陷。固体的基本力学行为由其应变能决定，并且能量通常是针对特定现实世界固体的行为定制的。 利用该团队的互补专业知识和先前为体积固体设计强大的新能量的经验，将为4型头发定义一种新的各向异性弹塑性能量，并将根据真实世界的测量结果以及广泛的大规模模拟数据对所产生的模型进行验证。 此外，对4型头发的详细了解将为跨越所有头发类型的表示指明方向;为了弥合这些类型，本研究将开发跨越股（1D），壳（2D）和体积（3D）制度的应变能的一般特征分析方法。项目成果将包括能够为人类头发产生逼真运动的有效方法，在其所有的多样性中。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Understanding the mechanics of human hair has wide applications in visual media and is critical to faithfully depicting virtual humans, because after the face, hair is the next characteristic that we look to when establishing a person's identity. However, almost all existing research has focused on the depiction of straight or curly hair, which spans Types 1 to 3 in the Walker hair typing system, whereas Type 4 hair, also known as afro-textured or kinky hair, has received almost no attention. This knowledge gap is unfortunate, because the naturally occurring hair type of millions of people in the United States, and a billion people worldwide, is Type 4; consequently, representing and simulating virtual Type 4 hair in digital media is difficult, because existing algorithms were not designed with its specific computational challenges in mind. More broadly, a comprehensive understanding of human hair is not possible without a complete investigation of Type 4. This project will address these deficiencies by developing new mechanical models and efficient computational methods for Type 4 hair. The fundamental mechanical behavior of a solid is determined by its strain energy, and energies are usually custom-tailored to the behavior of specific real-world solids. Leveraging the team's complementary expertise and prior experience designing robust new energies for volumetric solids, a new, anisotropic, elasto-plastic energy for Type 4 hair will be defined, and the resulting model will be validated against real-world measurements as well as extensive large-scale simulation data. Moreover, a detailed understanding of Type 4 hair will point the way toward representations that span all hair types; to bridge these types, this research will develop general eigenanalysis methods for strain energies that span the strand (1D), shell (2D), and volumetric (3D) regimes. Project outcomes will include efficient methods that are capable of generating realistic motion for human hair, in all of its diversity.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.