Foam will sample custom bubbles from its state of creation – the first frame. From then on, each new custome bubble created in Foam will be based on the current timeline indicator of the Foam composition. In short, Foam samples without any control over the start time of the custome bubble.
Particle Playground does that. CHeck out my COW tutorial on particle Playground entitled, Fun inParticle Playland.
Youmay also want to have a look at Cell Pattern for the effect you want and bypass Particle Playground altogether. The only problem here is that you won’t be able to have the cells multiply themselves to eventually fill up the screen. Well, perhaps with some major masking work you may be able to do it but it’s going to be a monstrous job.
Particle Playground is still your best bet.
You’ll want to use a small amount of repel to ensure that the particles do not overlap. It’s going to be tricky if you want to pull this off in a perfect manner.
HTH
Roland Kahlenberg
broadcastGEMs
customizable animated backdrops with Adobe After Effects project files