GPU Emitter Not Working Properly


So I realized something wrong was going on with my GPU emitters. They are not spamming as much as they use to, and the spam is inconsistent.

Let me show with pics;

Here is a GPU Particle Emitter of 4.10 . Its nothing but the standard one. Only things I included is an “initial velocity of 150-X” and “size by life going from 1 to 0 in one second” nodes. I am spamming the particle for 5000 times aswell.

Here is 4.10, all smooth;


Here is 4.11, with hiccups;


When you do it with a circle texture, its more obvious;

Here is 4.10;


And 4.11, obvious hiccups;


I will gladly help with any questions. It’s easy to produce so. Thanks!

Hi Achilleon,

I’ve entered UE-29009 for this to be investigated.

Thank you!


Same thing here. I’m going nuts!

Mr Tim,

Thank you for your time. I just want to let you know that the same problem is happening with ribbon data emitters too, and to a worse degree if I might add.

Just wanted to point out.

Got that one and reported it a few days ago with UE-29078. :wink:

We’re going to try and get these pushed out in a HotFix for 4.11 since they can impact more users, but unfortunately I can’t guarantee that will happen just yet. If they are in the HotFix they will be listed on the Update notes from the forums.

This was a deliberate change from what the ticket says.

Here are the notes from the ticket.

"If the user wants to target higher framerates while not supporting “low” framerates, he can disable the feature with:
“r.GPUParticle.FixDeltaSeconds 0”

If he puts a too small value like “r.GPUParticle.FixDeltaSeconds .005”, then low framerate systems will suffer extra cost because the simulation will be done several times (to the extent of “r.GPUParticle.MaxNumIterations”)
This is definitely a new behavior compared with the previous version, but to some extent the system must be designed to look acceptable at framerates around 30-60 fps. This special case binding the frame rate to the particle system look is what was intented to be fixed by the FixDeltaSeconds feature (it goes for high framerates as well a “slomo” replay)."

Thank you!


This seems to be a very hideous “fix” Mr Tim. It’s not that I will judge, but is it okay if I use that exec command on level blueprint with Begin Play Event?

Will that fix it? I am asking this as I am no longer using the GPU particle. Or won’t be for long. I just want to know if its possible that way or not. Thanks!

The problem with the original repro case, and the one I submitted the bug for was a very specific way to reproduce the issue. Using the methods mentioned above are going to be best practice for particle systems in this manner.