NEW: Join my free 100 Days of SwiftUI challenge today! >>

How to advance time in an SKEmitterNode using advanceSimulationTime()

Swift version: 5.1

Paul Hudson    @twostraws   

When you create a particle system in SpriteKit, the particles start at their creation point and move outwards from there. That’s fine for things like explosions and fire, but if you’re using the particles to simulate something that has no real start or end – space dust, for example – then having your particles start from a particular location looks wrong.

To fix this, you should use the advanceSimulationTime() method of SKEmitterNode: give it a number of seconds, and it effectively fast forwards the particle system by that amount. For a space dust particle system, this would fill the screen with particles, so the game screen doesn’t start empty.

Here’s some code:

if let starfield = SKEmitterNode(fileNamed: "Starfield") {
    starfield.position = CGPoint(x: 1024, y: 384)
    starfield.advanceSimulationTime(10)
    addChild(starfield)
}

LEARN SWIFTUI FOR FREE I have a massive, free SwiftUI video collection on YouTube teaching you how to build complete apps with SwiftUI – check it out!

Available from iOS 7.0

Similar solutions…

About the Swift Knowledge Base

This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.

BUY OUR BOOKS
Buy Pro Swift Buy Swift Design Patterns Buy Testing Swift Buy Hacking with iOS Buy Swift Coding Challenges Buy Swift on Sundays Volume One Buy Server-Side Swift (Vapor Edition) Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Advanced iOS Volume Three Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with macOS Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Server-Side Swift (Kitura Edition) Buy Beyond Code

Was this page useful? Let us know!