I did something fairly similar to this here: https://codepen.io/thomcc/pen/vLzyPY (I need to look into why this isn't running at 60fps anymore on my laptop, it certainly used to...)

The big difference is that it prerenders a gradient for each ball (it uses html5 canvas for that, but doing it with webgl is completely doable, although a bit more work), which is used as a distance field.