Scroll and show content by a midle circle

Hey guys, I’m trying to make a kind of hard interaction and I need some help.

The ideia is to scroll the website but when you reach the section with the bg texture the content start appearing by a circle from the middle, and when the circle is full screen, the content scrolls nomarlly.

Here is the design:
Anotação 2020-05-21 113215

Anotação 2020-05-21 113309

Any idea of how to make it?