why do particle effects often keep going in the background when you pause a game while everything else is frozen in place?

Question

why do particle effects often keep going in the background when you pause a game while everything else is frozen in place?

In: 315

Answer 1

Particle systems are possible because we do a lot of performance optimizations to make those millions of particles run at a decent speed. One of those optimizations is keeping the system as simple as possible. Particles use what’s called “Delta Time,” (time since last frame) to judge how much a particle needs to move that frame, and then a simple algorithm is used on each particle to move them into their new positions.

If you pause the game, suddenly the time since the previous frame increases dramatically, meaning if done incorrectly, when unpaused the particles would go “Oh, I need to move 1,000,000 frames worth of distance **right now**,” and cause some weird effects. While possible to mitigate, it’s much simpler to just allow particle systems to keep running.