How are backgrounds animated? I'm curious about how they are animated:


Flower petals in the air
Water effects (e.g the intro of The Garden of Words)


Water droplets in pond (00:17 and 1:35)
Reflection of a person walking (01:54)
Sun reflecting off water

Time-lapse (e.g Your Name)


Are backgrounds done frame by frame? Or do they use something like AE?
Technically, everything you list isn't a background in the sense used in traditional hand-drawn animation. A background is a static image, and anything moving is on a separate layer. One shot may have several layers. Flower petals are animated just like characters, for example, on their own layer(s).

I think what you mean are environment shots.

However, this gets more complicated with CGI. The examples you cite of water droplets are made with CGI; they're not hand-drawn (that's partly how the camera can tilt so effectively). Similarly, the reflection is made by taking the hand-drawn animation and placing it on the CGI-based water surface.

The time lapse you show is a trick of reversing the traditional layering. The foreground layer is made up of environmental objects like trees, while the sky is a fully animated layer. Someone's drawing those clouds and that sun, every frame, and it's just being placed on a layer behind the one containing the trees.

If by "AE" you mean After Effects, the Japanese animation industry generally uses software that's been built for specifically for the anime industry, like RETAS Pro. Some are integrated into the workflow, while others are standalone. But if an effect is being generated on the computer, it's generally classified as CGI, like the water droplets, regardless of the tool being used.