https://techcrunch.com/2018/07/13/disney-tech-smooths-out-bad-cg-hair-days/

Disney is unequivocally the world’s leader in 3D simulations of hair — something of a niche talent in a way, but useful if you make movies like Tangled, where hair is basically the main character. A new bit of research from the company makes it easier for animators to have hair follow their artistic intent while also moving realistically.

The problem Disney Research aimed to solve was a compromise that animators have had to make when making the hair on characters do what the scene requires. While the hair will ultimately be rendered in glorious high definition and with detailed physics, it’s too computationally expensive to do that while composing the scene.