Change particle Color with animation

🎤 General Discussion Swift
1

Hi,

I want to change the color of my particles in SCNParticleSystem from Color A to Color B using CABasicAnimation
I am retrieving color A via

let currentColor: UIColor = (targetColorSphereEmitterNode.particleSystems?[0].particleColor)!

and assign the animation by using

let targetColorAnimation = CABasicAnimation(keyPath: "particleColor")  
  targetColorAnimation.fromValue = currentColor  
  targetColorAnimation.toValue = UIColor.magenta  
  targetColorAnimation.duration = 1.0  
  targetColorAnimation.isRemovedOnCompletion = true  
  targetColorSphereEmitterNode.particleSystems?[0].addAnimation(targetColorAnimation, forKey: nil)

Problem is now that the app crashes when executing line 6 with

2017-07-27 18:22:32.039 ColorCube[14484:1136078] -[SCNParticleSystem copyAnimationChannelForKeyPath:animation:]: unrecognized selector sent to instance 0x7fc7916126f0  
2017-07-27 18:22:32.042 ColorCube[14484:1136078] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[SCNParticleSystem copyAnimationChannelForKeyPath:animation:]: unrecognized selector sent to instance 0x7fc7916126f0'  
*** First throw call stack:  
(  
  0   CoreFoundation                      0x000000011267db0b __exceptionPreprocess + 171  
  1   libobjc.A.dylib                     0x000000010f175141 objc_exception_throw + 48  
  2   CoreFoundation                      0x00000001126ed134 -[NSObject(NSObject) doesNotRecognizeSelector:] + 132  
  3   CoreFoundation                      0x0000000112604840 ___forwarding___ + 1024  
  4   CoreFoundation                      0x00000001126043b8 _CF_forwarding_prep_0 + 120  
  5   SceneKit                            0x000000010f9b31d8 SCNAddPropertyAnimation + 133  
  6   SceneKit                            0x000000010f9b3009 SCNAddAnimation + 431  
  7   SceneKit                            0x000000010f97f7d7 __41-[SCNParticleSystem addAnimation:forKey:]_block_invoke + 31  
  8   SceneKit                            0x000000010fa30aa4 C3DTransactionFlush + 2989  
  9   CoreFoundation                      0x0000000112623717 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 23  
  10  CoreFoundation                      0x0000000112623687 __CFRunLoopDoObservers + 391  
  11  CoreFoundation                      0x0000000112608720 __CFRunLoopRun + 1200  
  12  CoreFoundation                      0x0000000112608016 CFRunLoopRunSpecific + 406  
  13  GraphicsServices                    0x0000000115b35a24 GSEventRunModal + 62  
  14  UIKit                               0x000000010fd8d134 UIApplicationMain + 159  
  15  ColorCube                           0x000000010eb909e7 main + 55  
  16  libdyld.dylib                       0x00000001136a965d start + 1  
  17  ???                                 0x0000000000000001 0x0 + 1  
)  
libc++abi.dylib: terminating with uncaught exception of type NSException

Not sure what I did wrong here or is this simply the false approach to change the color of the particles?

Max

2

Hi @mattresstopper! Hmm that’s strange… I’m not too familiar with SceneKit but this should be working ok :thinking:

Maybe its due to the way that your emitter node is configured? Could you maybe share the code for that?

Also maybe take a look at the SCNParticleSystem docs as they describe a few ways that allow you to animate this class.

Hope it helps!