耶鲁研究如何为《玩具总动员5》打造计算机动画毛发
Computer animated hair in Toy Story 5
耶鲁大学 Kim 实验室的论文在 Symposium on Computer Animation 发表，研究模拟毛发所需的拉伸、弯曲和扭转三种能量物理机制，其弯曲能量数学模型被 Pixar 用于《玩具总动员5》角色 Blaze。论文共同第一作者为 Kim 实验室博士生 Alvin Shi 和 Haomiao Wu，团队还提出了一种与过去十余年做法不同的扭转运动模拟方法。
Kim’s research is working to change that. The paper, published at the Symposium on Computer Animation, delves into the physics of three types of energy needed to simulate a strand: stretching, bending, and torsion. For the character of Blaze, Pixar borrowed Kim’s mathematical model specifically for bending.
“If you want to take two ends of a piece of wire and bend it into a circle, this is the part of the material that will resist you,” said Kim. “It's called the bending energy, and we derived its eigenvalues, which is a key quantity that is needed to simulate it.”
Alvin Shi and Haomiao Wu, Ph.D. students in Kim’s lab, were the co-lead authors of the paper.
The Toy Story 5 creators also drew inspiration from the research to depict a twisting, or torsion, movement.
“You can think of it as the force that resists you when you grab two ends of a piece of string and try twirling one end so that the whole thing spins into a corkscrew,” he said. “We came up with a way of doing this that was very different from the way that others had been doing it for over a decade.”
Back when Kim was a research scientist at Pixar before coming to Yale, he worked with David Eberle, one of the Pixar animators who made use of this research for Toy Story 5.
来源：Hacker News · engineering.yale.edu