If I understand correctly, you ask how you change the texture or material information like in the gif?
It is a big sphere mask, that is uses lerp or step to hides another texture.
The base effect is described in this mini tutorial: https://www.patreon.com/posts/19355776
I have used this technique in a challenge sketch some time ago: Mathew Varkki: Sketch #18 WIP
You will need a script or Blueprint, that drives the value and provides world location information for the material.
There are many layers to the effect In the Kena reference.
- Initial burst with particles and refractive distortion
- Grass spawning
- Flowers grow
- Part of trees dissolve.
All of these materials have to be driven by the same parameters. But some of these have an offset, that they start later.
I hope this helps you.