Warm up time does nothing with GPU Particles in UE4.4.3

Development Asset Creation FX
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1

Hello everyone.

Just as the title says. With the previous version I used, 4.2.1, I could enable warm up time to GPU particles and it worked fine. But in the current version, 4.4.3, that doesn’t work anymore. When I hit play or simulate, particles start playing again from the beginning. With normal particles it works fine.

Does anyone know the reason of this? Thanks.

2

Hey PacoChan -

Can you share your Particle Setup? I am not able to reproduce this issue in house.

Thank You

Eric Ketchum

3

Thanks for your answer.

It happens even with the most basic setup:

  • I create a new blank project with no starter content.
  • I create a new Particle System.
  • I drag it to the scene.
  • I open cascade and set Type Data to GPU Sprites.
  • I set Lifetime to a Constant 10.
  • I set Warmup time to 5.
  • And I set fixed bounds.
  • When I hit Simulate or Play, particles start from the beginning, like if I had zero Warmup time.
  • If I remove the GPU Sprites module, it all works ok.

I’ve done some more testing:

  • If I package the project, it works as expected, both in Development and Release configurations, so it seems that it happens only in the editor.
  • Sometimes it’s happening in UE4.2.1 version too.
  • I recently changed of OS. Before I used Windows 7 x64 and now I use Windows 8.1 x64.
  • In Windows 7 I never had this problem with UE4.2.1. I’m not sure with UE4.4.3.
  • Since I upgraded to Windows 8.1, I had some graphic issues due to nVidia graphics drivers (reflections flickering all over the place). I updated the drivers from version 340 to the last version, 344, and it solved the problem.
  • Maybe this GPU particle issue is related with my OS, drivers or something like that?

This is all the info I can think of. Thanks for yout attention :slight_smile:

4

Hey PacoChan -

I created a quick test that is working correctly on my CPU and I want to make sure that it is working for you. Unzip this project to a new folder and double click the *.Uproject file. PIE and let me know how many times the particles cycle before disappearing.link text

Thank You

Eric Ketchum

5

Hi again, Eric.

The particle system cycles two times and then disappears.

6

So Warm Up Times are working. If you go into the Particles emitter and change the warm up time to 0 it will cycle 3 times. How are you trying to use the warm up timer specifically, there is probably a setup issue that is causing you problems.

Let me know -

Eric Ketchum

7

Hi again.

I’ve modified your scene. I added to the right of your particle system a basic GPU Particle system like the one I mentioned before. And to the left, the exact same particle system but with no gpu particles.

I also send you two screenshots of how the particles behave in my PC:

This is in the editor, just after hitting Play. GPU Particles are not working as expected:

16912-ue.jpg
16912-ue.jpg1920×1049 362 KB

This is in a packaged build, just after executing AH_GPUTest.exe. GPU Particles are working as expected, just like the ones in the left:

16914-ue_2.jpg
16914-ue_2.jpg1616×938 343 KB

As you see, there’s something wrong here.

I send you back the modified scene:[link text][3]

Greetings!

8

Sky lives by it’s own life as well.
But warmup working inside Cascade (reset by ‘space’) and release, so it’s fine at least.

9

Hey PacoChan -

Thank You for the clarification it was the looping that got me. I have good news, the fix is already in place and should be pushed out with the next release version of the engine, 4.5.

Again Thank You

Eric Ketchum