It's a bit of a kind of transparent material, like a raincoat. It's very soft and thin. What kind of material is this?

It's a dress, not a raincoat. It is now popular with this material. There are also made with this material sunscreen.

You said that the film can be made of polyvinyl chloride (PVC) or polyamide plastic (PA) polycarbonate plastic (PC) above which can be processed into a film, I do not know exactly what kind of raincoat

I've seen it on Taobao, it's pretty good..

Taobao has a sunscreen on sale