This network utilizes a Stream POP to birth new particles based on the particle density per unit division of space where to particle streams flow and collide. Thelower the threshold, the less particles needed to trigger new particle birthing by the Stream POP.
Some particles are birthed from a grid and are then subjected to a vortex force.The drag is needed to prevent the blue particles from continually expanding while keeping them moving in a circle.
After about 140 frames, the ring should be fully formed and now a spray of red particles start shooting off from the center of the ring (birthed by a circle source geometry).
These two streams are fed into the Stream POP. The Stream POP will birth particles where the two streams intersect. It does this by spatially subdividing the area where the particles flow, and then measuring the particle number within the.