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I'm trying to animate a PFX particle system in the UE4 sequencer, and I can't see anywhere to add an animation track for a PFX system parameter. With a regular actor, I can expose variables easily by checking the box 'Expose to Cinematics' which lets me sequence the variable with keyframes on a timeline.

I need to update the parameters of my PFX component on a UE4 timeline to match the animation, by controlling the values of the particle system parameters with keyframes.

How is this possible? Thanks!
by phong (320 points)

1 Answer

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Hi phong,

by parameters I supposed you mean effect attributes ? If so indeed it is not implemented right now in the plugin, and we'll dig into it when we have some time but as I recall in previous UE4 versions, adding custom tracks to matinee was impossible without modifying UE4 source code (by custom tracks I mean third party code to animate custom data through Matinee curves). They might have opened their API a little bit more, I'll update this thread as soon as I can get my hands on it.

What you could do however is use an intermediate blueprint variable, that you expose to sequencer. Then, in this blueprint's tick function (or other), set the effect attribute based on the newly animated value:

In the above example,

  • Emitter is a reference to the target effect to have its "UpScale" attribute animated
  • FloatAttribute is the BP exposed variable and animated in sequencer
  • OffsetAttributeIndex is the stored index value of the attribute as we do "SetAttribute" each tick, it's not a good thing to use "FindAttributeIndex" each frame
Another solution is also to use a BP timeline directly.
Those solutions are far from ideal for things like tick execution order between matinee and BP, but this can be a good fix for now.
Hope this helps while we can improve our integration with Matinee/Sequencer

by HugoPKFX (17.7k points)
Thanks Hugo, that's what I figured. I implemented something like what you suggested here, thanks for the affirmation. Very helpful to know that the extra legwork is required at this stage. Looking forward to a future version of PFX where the parameters are editable directly in the timeline! Great work on everything.
This works only in gameplay not in sequencer, at least for me....