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，对于忠实地描绘虚拟人至关重要，因为在我们建立一个人的身份时，头发是继脸之后的下一个特征。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Walker头发分类系统中，直发或卷发的类型从1到3，而类型4的头发，也被称为非洲纹理或卷发，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10亿人自然产生的头发类型是4型；因此，在数字媒体中表示和模拟虚拟4型头发是困难的，因为现有算法在设计时没有考虑到其特定的计算挑战。更广泛地说，如果没有对4型头发的全面研究，对人类头发的全面理解是不可能的。这个项目将通过开发4型头发的新的力学模型和有效的计算方法来解决这些不足。固体的基本力学行为由其应变能决定，而应变能通常是针对特定真实固体的行为而定制的。利用团队互补的专业知识和先前为体积固体设计强大的新能源的经验，将定义用于4型头发的新的、各向异性的弹塑性能量，并将根据真实世界的测量和大量的大规模模拟数据对结果模型进行验证。此外，对4型毛发的详细理解将为跨越所有毛发类型的表示指明方向；为了连接这些类型，本研究将开发跨股(1D)、壳(2D)和体积(3D)区域的应变能的通用特征分析方法。项目成果将包括高效的方法，能够在所有的多样性中产生人类头发的真实运动。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.