I'm trying to make an effect where some objects get inflated along the normals until they fill another container object.

When there is only one object, it can be easily done with Ray SOP:



However, when it comes to multiple objects, I have no idea how to achieve the effect:



I guess I need to get some solver involved? But I don't even know where to start...

You could try something like this vellum set up.
https://hdbp.io/ztbfmcjG [hdbp.io]

Enivob
You could try something like this vellum set up.
https://hdbp.io/ztbfmcjG [hdbp.io]

Using Vellum seems to be a possible solution. I found this one:



However I feel there must be a more performant way... since I just want the points to move along the normals, do I really need a physical simulation for this?

- may be this tutorial can guide you

Analytical Foam

https://entagma.com/analytical-foam/ [entagma.com]

As position based simulation techniques ...

You could also solve this with signed distance fields, I remember an introduction by entagma on this topic, but I don't remember exactly which tutorial. Using two spheres growing in a sop solver taking collisions into account.