In the cases of Brave and Moana at Pixar and Disney Animation respectively, the story definitely came before the tech was developed. I was an intern at Pixar during the production of Brave, and I worked on Moana, and I can say that in both cases, there was a mad scramble to develop the tech to catch up with the story. We didn't really have the water on Moana working completely correctly until like 6 months before the movie came out.
Parent comment was edited after this post, so now this reply seems out-of-context. The parent comment originally made a comparison to Pixar and Disney Animation coming up with hair and water tech first and then coming up with stories for Brave and Moana respectively to wrap around the tech.
That's so interesting! I think the fact that they nail the tech so well makes it intuitively surprising that it didn't come first. Not pixar but similarly, when I saw the siggraph talk where Disney Animation showed off how they do snow rendering in Frozen I wondered whether the tech came first
That's also a case where the tech came a while after the story. Our early snow tests on Frozen looked pretty terrible until the MPM simulator [1] came online later.
Did the MPM simulator get used in practice for Frozen? I talked to a few sim TDs (or whatever the equivalent Disney title is) and they said it was too slow at the start for practical use!
Same for Nemo 2. One of the first scenes (Octopus in the Zoo) was only finalized after 2 years because the puppetry and shading of the Octopus took a lot of R&D to implement
I have to imagine the Pixar shorts are, however, a way to do this kind of technical experimentation to better render mediums between stories? Some examples for me include the sand / features rendering in Piper, and the water rendering in Lava? I guess that's more of a question - are those used as tech platforms, or story platforms to test teams? (Either way, a good way to do it!)