I don't see a concrete question. There are 25 examples on the page you link to. And all of them link to Jared Tarbell's site where you can download the source code. So what's the problem?

Thanks, I didnt see there was the code. I was looking for a hint to make that. I see that Jared Tarbell dont try to simulate a pencil but grains of sand dropping. The way I was tryng that was not the correct.