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Dynamic Parameter Expression doesn't seem to work with Beam Particles

I'm trying to make use of a Dynamic Parameter Expression in a particle system, in order to pass data to its material. I have set it up in pretty much the same way as the example here:


Everything seems to work fine while using standard particle sprites, but if I try to use a Beam type, the data just doesn't seem to get sent to the particle system.

I have tried various things but have drawn a blank. Does anyone know if this is a bug or if there is a way around it? I am running from source so I can make changes to the code if necessary, but I just need to get this working.



Product Version: UE 4.12
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asked Aug 17 '16 at 03:40 PM in Bug Reports

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avatar image Davision Oct 01 '16 at 12:15 PM

Did you found a workaround for it?

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2 answers: sort voted first

Hi Michael,

This is actually a known issue that you can track here: https://issues.unrealengine.com/issue/UE-13679 It looks like the issue is backlogged but you can draw attention to it by voting. We gauge community interest by number of votes on an issue!

Thank you for submitting this report,

Ed Burgess

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answered Aug 18 '16 at 02:09 PM

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Just found a workaround for this. You have to do this: https://answers.unrealengine.com/questions/356404/parameter-material-module-in-cascade.html and then you can change material parameters of the particle material like you would do with any dynamic material.

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answered Oct 01 '16 at 12:55 PM

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avatar image MichaelBibby Oct 03 '16 at 08:19 AM

Thanks for the suggestion, however in my case this isn't actually what I need.

Your solution will work well if the material needs to be updated by some logic in a blueprint or code tick function, however in my case I want the particle itself to send the data via a curve over the life of the particle.

If you see the example linked in my original post you can see that the system is designed so that an emitted can define an output parameter (using a curve or uniform distribution for example) and that output is sent directly to the material. This way there is no additional tick function required to update the value (so is more efficient) and the particle has no need of any additional logic to function correctly, making the whole thing much less complex and error prone.

In my case I ended up using the particle colour parameter to send the data (which is really not ideal because it meant I couldn't use it for colour changes, but in my case it worked because I didn't need to change the colour of the effect over time).

If anyone else comes accross this same issue, I suggest you vote for it to be prioritised as Ed suggested above https://issues.unrealengine.com/issue/UE-13679


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