https://twitter.com/seijikanoh/status/761533112257957888
https://twitter.com/seijikanoh/status/761533325135581185

the loop

These cuts are amazing. I have heard it took them 1 year and 7 months to just animate the scenes with the Tatarigami (wild boar). I thought it was CG but its hand drawn

This is insane. It must've taken a crazy amount of work to complete these cuts.

mikasa said:
I thought it was CG but its hand drawn

Didn't they originally intend to do this in 3D but the quality wasn't good enough so they combined 2D and 3D in some way. Perhaps the animators animated the eels on top of a 3D model to help maintain forms. I can't remember.

alleksi said:
Perhaps the animators animated the eels on top of a 3D model to help maintain forms

The boar is hand-drawn, and then they used CGI to animate the "eels".
The process is documented in もののけ姫はこうして生まれた documentary.

Habarudo said:
The boar is hand-drawn, and then they used CGI to animate the "eels".
The process is documented in もののけ姫はこうして生まれた documentary.

there are only a very few select shots that have cgi worms, almost all of the shots are completely hand drawn. They did use some minor digitally composited shading on the boar creature but that's it