Every Pixar film tackles a different technical problem.

1. "Toy Story" (1995): realistic lighting surfaces like plastic and metal toys
2. "Finding Nemo" (2003): underwater scenes
3. "The Incredibles" (2004): realistic human characters and fabric simulation.
4. "Cars" (2006): large-scale environments.
5. "Wall-E" (2008): realistic dust
6. "Brave" (2012): hair and fur simulation
   …

It’s super interesting that for this movie the challenge was to animate the fire characters realistically (as fire) but also recognizable (as characters). Using AI is a very neat approach.