Particle System Culling Issue, please help explain this to me

Hey guys,

So I've been running into a problem. I have a large 2D scene with lots of rain particles, and the rain particles collide on the level geometry. Naturally, this has a ton of overhead.

So I figured I would take advantage of Unity's handy culling system, and simply just slice up that rain particle system into multiple pieces, like so:


My understanding was this: since Unity supposedly won't render/simulate the particle systems that the camera cannot see, I'll get to effectively cut my physics collisions etc to only which section of the rain is being shown on the camera right now.

But here's the problem: I can't get the culling to work.

Whenever I try this method, even though only Particle system A is visible on both editor and game cameras, the overhead from B and C still exists, which means that it is still being simulated. If I deactivate the game objects of B and C, the overhead goes down.

So, what's the deal? Is there a step to particle culling that I'm not getting? I already searched the net, but ironically most of threads about culling is about how to turn it off, not on. And the scale on all the systems is 1,1,1.

 

Hey Karl, thanks for the quick response! It's a relief to know that it's a known bug, at least. Hopefully it will be fixed before long, as it's a pretty big one! I'll keep the workaround in mind until then, thanks.

 

Hey Karl,

I tried one of the workarounds (instantiate them from script at start) but no dice. Does the editor view affect the culling at all, or just game view? In any case, I instantiated 5 rain systems on scene load, only 1 was visible from either camera; but the other 4 were still calculating physics/rendering.

 

Hmm, no workarounds working for me unfortunately on Unity 5.4.2f2

Tried:

- Instantiating from Script
- Instantiating from Script in Front of Camera at scene start, then moving them by script to correct locations.
- Placing Particle systems in front of Camera in scene, and then moving by script to correct locations at scene start.
- Tried wildly moving particle system in front of camera and then moving it far away.

 

Here's the settings on the parent particle system: http://i.imgur.com/sxFQjZq.png

 

@karl_jones did any settings on the particle system prevent the culling, do you think?

 

Gotcha.

I guess I'll have to do culling myself then by having triggers turn adjacent particle systems on and off; raindrops with collision over a wide area is just too expensive otherwise.

 

Sounds good! Looking forward to reading it.

 

I recently found the blog written by Karl noted in this thread.

I am curious if there is API for the ParticleSystem component that allows us to determine if the system is in procedural mode or not? This would be useful to access both at run time and in the editor.

I perused the documents, but did not find anything that seemed directly related.

 

It would allow me to do static or runtime filters of systems that may not be setup efficiently because they are not culling.

An example would be an editor script that runs through the assets and locates the ones that would not cull for evaluation. Not all developers making particle systems will be aware of the impact of their settings on the culling and many of them will miss the tiny visual warning icon.

 

Does this still apply? Im getting a huge amount of particle systems "alive" in my game, even when theyre no where near me. The little bubble message is not there on any ive tweaked them all so they should be cullable, but right now have 200+ alive particle systems, how do I stop them playing until I see them ? IE, why wont they cull?? Confused by that.

 

Thanks I have read that quite a few times today, great work. But I dont think Im using things that aren't cullable, if they are able to be culled the little message bubble vanishes right? Ive gone through made sure that does not appear on any particle system, so I assumed they would all be cullable. But yet still 250 of them exist all over my scene and dont go off even when frustrum does not contain them. Or maybe the message bubble is misleading, there are other things that stop it being culled?

 

No there appears to be no script on them. I ticked bounds they are static, "resimulate" is ticked is that an issue? also "play on awake" is ticked, any issue ? I also have set them to static, not sure if that helps. They arent huge particle systems just some from pipes etc.

Is emitter velocity - rigidbody an issue?

 

Thanks! I will try but its absolutely huge!..

edit: struggling with zipping it! Could I make a video showing everything in detail instead?

Error compressing TAR:
7-Zip (a) [64] 16.04 ZS : Copyright (c) 1999-2016 Igor Pavlov : 2017-03-20

Scanning the drive:
18320 folders, 65373 files, 26201855861 bytes (25 GiB)

Creating archive: Z:\GDV16\GD\Temp\archtemp.tar

Items to compress: 83693



System ERROR:
There is not enough space on the disk.


0x00000001411B000B (Unity) StackWalker::GetCurrentCallstack
0x00000001411B288F (Unity) StackWalker::ShowCallstack
0x000000014108CA30 (Unity) GetStacktrace
0x0000000140596DA3 (Unity) DebugStringToFile
0x0000000140597581 (Unity) DebugStringToFile
0x00000001412A6369 (Unity) CompressPackageTarGZAndDeleteFolder
0x000000014103E4D3 (Unity) ExportPackage
0x0000000141050C67 (Unity) TickPackageImport
0x00000001410C4504 (Unity) Application::TickTimer
0x00000001412CC349 (Unity) MainMessageLoop
0x00000001412CDC04 (Unity) WinMain
0x0000000141DE45A8 (Unity) __tmainCRTStartup
0x00007FFD12981FE4 (KERNEL32) BaseThreadInitThunk
0x00007FFD1307EF91 (ntdll) RtlUserThreadStart

 

I made a video where I tried to show everything, maybe this helps? Much appreciated.

 

Thanks I guess I should add the check for automaticCullingEnabled to my script (once I upgrade to 2018, still on 2017.2 since upgrading broke some assets) that may eliminate things I think are alive, but its very weird particle numbers change. So I should not have particle systems looping ? but wont they only play once and then stop ? Im fast starting to think I should use the same optimisation I do on my npcs using some form of onBecomeVisible/inVisible and maybe a cube somewhere in the particle system to trigger it.

Also im not actually changing anything during runtime, in that demo I may have ticked or unticked somethign that broke culling on one, but not all the others. And if you watch later on in video the water in the fountain is not changing boundaries, and still isnt culled (I dont think). My debug script simply gets an array of them and lists them out.

I will try deep profiler again but most of the time it simply points to an object called "NA" which leaves me guessing again. Much of the optimisation I need to do is plagued by this very issue, and I never understood why. No one does But unity keeps you guessing until lunchtime the next day before you find it.

Thanks for all the help, this week I have optimised absolutely everything, just need to finish off particle systems to get full speed benefit. Some weird unrelated things I noticed were: character controllers are heavy on physics/cpu, even sleeping and or kinematic rigidbodies are also heavy on the physics (now trying to turn these things on just in time with a trigger), never use physics in particle systems and this one, particle systems are tough to cull lol... Cheers!

PS. A great service from unity would be you pay to spend a week with some of the devs who help you fix all the niggles you cannot do, and spot optimisations etc, even as an indie Id prob put down £1000 to fix all my issues and have someone help me optimise. Or they could just do it for love lol.

 

Im now using 2018.1 but I dont see "automaticCullingEnabled " ?

 

oh yes it does compile sorry just VS putting red line under. The funny thing is im not sure how much this helps, I was hoping for a variable more like isCurrentlyCulled. In my script which shows all particle systems which are alive, playing and have automaticCullingEnabled it still lists 250. Now am I misunderstanding or does this mean the particle systems are going all the time even when im not looking at them ? Maybe I got too far into trying to optimise/cull particle systems and im misleading myself, I just want to know which particle systems are actually wasting time in the background when I cannot see them, and to do something about them. I dont mind doing the custom culling thing if it needs to be done but I assumed unity would do this for us.

 

Thanks! Ok great so now all my particle systems seem to have automaticCullingEnabled as true now, so I assume when they're not in my frustrum they are now being culled. It's still misleading to know for sure though because they still all appear on my list which checks: if (p != null && p.isEmitting && p.IsAlive() && p.isPlaying), if it gets past that then it will show up in my list red if !p.automaticCullingEnabled, and none of mine are red. But, why then do they still appear in the list claiming to be emitting (and I see particleCount changes on some of them, not many but seems to go up and down by 1 or2 still) even when out of the frustrum ? I expected that as I move around and my list updates, that the list of particle systems would grow and shrink depending on which ones are in my frustrum. Very sorry to keep labouring this point but it seems to contradict itself, ie if auto culling is working (and theyre not in frustrum) why do they claim to be alive, emitting, and playing, unless all of these methods are bugged somehow? I think I read even when they're culled they will still report being alive and playing, but I assume they should not be reporting isEmitting as true. Thanks again for all the help.

EDIT: im assuming now even when culled isEmitting wrongly returns true, and I am just trusting they are culled, since after closer inspection their particle count does pretty much stop still when they're not in the frustrum, so I will change my script to only keep them in the list if particleCount keeps changing. If that is correct then I have what I want, they're culled, and my list will show only alive ones, which will change depending on where I go in my level. Thanks.

 

Hi @karl_jones,

I'm using your custom culling component for particles and I have to comment automaticCullingEnabled code to fix an error. How I can solve it correctly? I have some systems I want to use yours instead of the default Shuriken procedural system.



Thanks in advance!

 

Hi @karl_jones and thanks for your fast reply,

I'm using 2018.4.23 version. The main reason to still use the script is to customize the bounding box. In some group of particles I can see a bigger one than what I see: Because I'm using a geometry with a dissolve, stretches billboard or things like that. For this reason, I want to adjust the BB to cull as many particles I can.




If I'm using the script, what performs better? Set the culling mode to Automatic or Always Simulate?

Seems everything goes fine now! Thanks!