How realistic are you intending for this to look? This is something that, if you desire realism, would be much better to shoot practically (with a dummy or stunt person, depending on the type of balls you want).
If you’re creatinga cartoony look, it could be relatively simple. You could use your favorite particle filter (Particular is a good one) with a custom particle of a ball and have it pouring balls down. Then, on separate layers, you could create the forming pile.
What are you actually going for?
– The Great Szalam
(The ‘Great’ stands for ‘Not So Great, in fact, Extremely Humble’)
No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.