Particle System preview scrubbing by script

I want to reproduce the behaviour of the Particle System where one can change the time of the ParticleSystem and see it at particular playback positions.

This can be done with the "Playback Time" but I need to do it by script.



I only need this to work in editor mode and not in playmode.
I tried using ParticleSystem.Simulate and ParticleSystem.time to no avail.
How can I set the Playback Time value of that popup window by script?

Code (CSharp):

1. // my failed attempts
2. if (Ps != null)
3. {
4.     // Ps.Simulate(adjustedTime, true, false);
5.     Ps.Pause(true);
6.     Ps.time = adjustedTime;
7. }

 

Ah yes, the restart parameter I had forgotten about that.

I thought the script would allow to preview properly but something's amiss.
An issue I found was due to the particles having a different seed @ every simulation. But there still are deeper problems and I really hope you can take a look at this: I provided a package of the example I show in the video.

Here's a video of the difference between clicking on the Particle System's Restart button and the ParticleSystem.Simulate by script.
As you can see the 1st particle isn't disappearing and the blue one can't even be seen going up.

Why is it behaving like that?

Code (CSharp):

1. using UnityEngine;
2.  
3. [RequireComponent(typeof(ParticleSystem))]
4. [ExecuteInEditMode]
5. public class TestAnimate : MonoBehaviour
6. {
7.     [Range(0,3f)] public float Timeline;
8.     private ParticleSystem Ps;
9.  
10.     void OnValidate()
11.     {
12.         Ps = GetComponent<ParticleSystem>();
13.         Ps.Simulate(Timeline, true, true);
14.         Ps.Pause(true);
15.         Ps.time = Timeline;
16.     }
17. }

 

When I'm moving the playback time when the particle system is paused, it works perfectly.
It means that the Editor is calling something that allows to preview without bugs, I just need to call the same thing then.

What is the editor calling when modifying this value?
Or how can I set that value to something I want through script?
I only need this to work in the editor and not in playmode.

 

Thanks a lot for answering all this Richard, it's much appreciated!

I will have to use the reflection temporarily until you find out how to fix that bug because my vfx artist needs that previewer asap. However, I haven't used reflection yet so do you know why it's not finding the PsUtils in the SetPlaybackTime() method here?

Code (CSharp):

1. using System.Reflection;
2. using UnityEngine;
3.  
4. [RequireComponent(typeof(ParticleSystem))]
5. [ExecuteInEditMode]
6. public class TestAnimate : MonoBehaviour
7. {
8.     [Range(0,3f)] public float Timeline;
9.     private ParticleSystem Ps;
10.  
11.     protected static MethodInfo Resimulation;
12.     protected static FieldInfo PlaybackTimeField;
13.  
14.     void SetPlaybackTime(float _time)
15.     {
16.         if (PlaybackTimeField == null || Resimulation == null)
17.         {
18.             var PsUtils = typeof(UnityEditor.EditorUtility).Assembly.GetType("ParticleSystemEditorUtils", true);
19.             PlaybackTimeField = PsUtils.GetField("playbackTime", BindingFlags.Static | BindingFlags.NonPublic);
20.             Resimulation = PsUtils.GetMethod("PerformCompleteResimulation", (BindingFlags.Static | BindingFlags.NonPublic));
21.         }
22.         PlaybackTimeField.SetValue(null, _time);
23.         Resimulation.Invoke(null, null);
24.     }
25.  
26.     void OnValidate()
27.     {
28.         Ps = GetComponent<ParticleSystem>();
29.  
30.         SetPlaybackTime(Timeline);
31.     }
32. }

 

Are there any plans to fix the long standing simulate bug in the unity 2019 cycle? My project is totally dependent on this working, been waiting a while, it'd be nice to know if I should just scrap it and move on.
https://issuetracker.unity3d.com/issues/particle-system-simulate-issues

 

Also an annoyance for us. It ate quite a few hours and I was beginning to suspect I was going insane for a bit.
I used a pile of hacks to get it somewhat working, but would appreciate a lot if it was officially fixed.

 

Thanks for the reply, I'm quite sad this isn't at least in the pipeline since it's over 3 years now. Would really appreciate anything you can do.

 

I only need play mode bug fixed. I do not need editor mode fixed. Sorry, I posted on this thread because it seemed most active and relevant. Many thanks for looking into it.

 

First, thanks Richard for looking deeper into this issue.
I never managed to use the trick with UnityEditor.ParticleSystemEditorUtils you had once mentioned.

Could it be that the play and editor mode bugs are one and the same?
There shouldn't be a doubt as to whether there is a bug in the editor mode with what I showed in the video above by the way. I could make a project with the scripts and post them as a bug if they are indeed different bugs.

Can we expect a bugfix for Unity 2018?

 

I'll leave it to you then . Good luck with the bugs, squash em good.

 

Thanks Richard, you're the best! Fingers crossed it passes testing...

 

Code (CSharp):

1. void SetPlaybacktime(float _time)
2.     {
3.         if(PlaybackTime == null || Resimulation == null)
4.         {
5.             var PsUtils = typeof(UnityEditor.EditorUtility).Assembly.GetType("UnityEditor.ParticleSystemEditorUtils");
6.  
7.             PlaybackTime = PsUtils.GetProperty("playbackTime", BindingFlags.Static | BindingFlags.NonPublic);
8.             Resimulation = PsUtils.GetProperty("resimulation", BindingFlags.Static | BindingFlags.NonPublic);
9.  
10.             getPlaybackTime = (Func<float>)Delegate.CreateDelegate(typeof(Func<float>), PlaybackTime.GetGetMethod(true));
11.         }
12.         PlaybackTime.SetValue(null, _time, null);
13.     }

There is no change when you change the playback Time by calling PropertyInfo.SetValue in the above way. is there any other way?

 

Understandable it wouldn't be fixed so soon, it does seem like a fundamental change. 2019 cycle would be great, thanks for the hard work on it!

 

If so, can not you use Simulate perfectly with the current Unity version?

 

That's awesome! Can we expect a backport in the 2019.1 cycle as well?

 

Good job man

 

Pitty. But stoked to see this fixed anyway. It is a really annoying thing that cost us many hours.
We'll finally be able to have proper edit-time particle sequence editing with our cutscene and time rewind stuff.

Thanks for getting it done!

 

Heck yeah! Can't wait to try it out. Sooo appreciated.

 

Looks like it is fixed on 2019.2 any chance fix for 2018.4 LTS cycle ?

 

For those passing by who get randomized results every time they use Simulate, please verify your children particle systems all have the "random seed" box unchecked ^^'