Inspired by the ideas in this discussion I thought it would be challenging and fun to have a go at creating my own version.
In my sketch the interaction shape is defined by the circumference of a circle cotangent to the two blobs. It calculates the circle radius from the combined sizes of the blobs and a tweak factor. With a known radius it is a simple matter to calculate the centre of the cotangent cicle and use these details to define the clipping regions used to draw the blob interactions.
This algorithm is similar to the one suggested by @solub in the linked discussion.
Enjoy 