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constant lag spikes when navigating scene...

I get constant lag spikes. during these lag spikes i get often.. its the game ms, draw ms and gpu ms that all spike at the same time ... same huge spike for them all.. and game ms is normally down since nothing is really going on in the scene.

Im talkn a spike from 3 ms to 40... some times 60 ms. Its only a moment.. just a spike as i float around my scene... turn the cmaera.. stuff like that. But it makes everything unplayable.. does not happen on my 4 ghz i7 with gtx 980, but happens on a 3.5ghz i7 with gtx 590.

Product Version: UE 4.9
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asked Oct 22 '15 at 09:04 PM in Rendering

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avatar image kurylo3d Oct 30 '15 at 04:44 PM

If its any help.. the lag spikes are almost completely gone when i disable texture streaming. The only minor lag spikes now are when certain areas of my level unexpectedly jump an extra 600 draw calls and then fall back down if i stand still.. any idea what i can do about that? I have had previous discussions with others over there at epic about texture streaming being bugged. Seems to be a broken feature.

avatar image Logan Bailey ♦♦ STAFF Nov 02 '15 at 04:37 PM

If you have narrowed it down to a specific issue please open another thread titled Texture Streaming. Perhaps there is a more specific issue happening using that feature. I can look into known reported issues with Texture Streaming in the meantime.

avatar image kurylo3d Nov 02 '15 at 04:52 PM

Sorry i have like 4 posts about lag issues.. so im trying to update them accurately in case anyone searches for this problem on their own. I will say the lag spikes every 10 feet of movement disappear with texture streaming gone, but the lag spikes remain for turning the camera 180 degrees... it will do it in any spot in the map.. every time... Actually it will do it the first couple of tiems.. but after rotating 360 degrees a few times that spot wont have the lag spike until i move on... Its odd because texture streaming is off now so i wouldnt know why turning the camera the first couple of times in a spot would cause a lag spike since everythign should be loaded up already..

Oh and not to be rundant since i have other posts on it. but, the other posts are cluttered so i will jsut tell u some other info here.

I tried screen percentage... and even when the screen is at 25% and running at 90 fps constnatly.. i still get the lag spikes.

Its very strange because lowering the screen percentage lowers the draw ms... to like 8 ms... and keeps gpu at like 30 ms... where as if its at 100% both gpu and draw ms are in the 30s... It really makes no sense since gpu would be the thing that is effected with screen percentage if im nto mistaken...

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2 answers: sort voted first

The reason for the lag is a hardware issue between the two graphics cards. Draw calls can influence your CPU/GPU in more ways than just the draw calls. For instance, if you had 400 trees in your scene and they were all 250 triangles, this would be less intense on your computer than 400 trees that are 1000 triangles. These of course being individual mesh's that are their own draw call as opposed to foliage.You said the geometry isn't intensive. Not intensive as in 500 tris and below or 25,000 and below?

If you are using HLOD's there is a known issue with the LOD's popping in all at once. So say you have a bunch of foliage. And then you add the HLOD system to handle the different clusters. Instead of a gradual LOD transition of your LOD's, based on culling, a number of LOD's all pop in at once when changing your FOV. This could be causing the issue where you walk every five feet and then your LOD's transition. This causing those draw calls to be called with the rest of your calculations when running UE4.

Yes, the GTX 580/590 is reasonably adequate. It will run modern games ok. However, the difference between developing a game and running a game is one is packaged. All of the development is over. Everything has been optimized to run within certain specs that is specified by the company to run their product. All of the functions, tools, calculations, that are associated with the development software are not present and the functionality of the game is all that is running on your machine.

The fact that you are able to work fine on a higher end machine is indicative that there is an issue from one machine to the next. You said "heaven forbid i attempt to use that in unreal engine 4," enforces this theory further. If you have a machine that is able to develop I would recommend using that machine for your development.

This directly correlates to the issue you previously posted : https://answers.unrealengine.com/questions/308110/profilegpu-not-accurate.html

Andrew Hurley has already given multiple links to our documentation regarding optimization and how to profile your GPU within your project. I can open the Blueprints map from learning and it doesn't dip below 80 or 90 fps on this setup.

OS Windows 7 Professional

Intel(R) Xeon(R) CPU ES-2620 0 @ 2.00 GHz 2.00GHz

32GB Ram

GeForce GTX 770 Version 347.09

Since you have already posted on this issue before, and I have looked through the thread, without a project I cannot begin to test whether the issue is project or card based. Based on all of this information I believe the issue lies either within your card or possibly your project.


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answered Oct 23 '15 at 02:19 PM

avatar image kurylo3d Oct 23 '15 at 03:45 PM

I have tried those profiler tools, but its difficult to get a grasp of the meaning behind what your reading. Some documentation would be epic.. no pun intended. Aside from that how would i record the moment of the lag spike? I mean running a command to profile would mean id be running it after the lag spike.

avatar image Logan Bailey ♦♦ STAFF Oct 23 '15 at 03:54 PM

Here is a link to our performance and profiling documentation. I believe the bottom of the page dealing with FPS will be of particular interest.


It's true the profileGPU command takes a snapshot of the current frame. However, since your issue deals directly with FPS this should help. Finding out where and when your spikes occur accurately you can then delve into what is costing your GPU/CPU so much.

This is a link to our profiler that deals with what different tabs within the profiler pertain to. Also I will link you to our CPU profiler that is dealt with in a similar fashion.




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Hlelo kurylo3D,

From your comparison and what you describe I believe this is a graphics card issue. In comparison between the 590 and the 980 the 980 has almost double the Engine and Memory Specs.


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answered Oct 22 '15 at 09:37 PM

avatar image kurylo3d Oct 22 '15 at 11:51 PM

Yes but how is it i have lag spikes even in places where i have 400 draw calls and am going 60 frames per second.. Majority of my scene is 30 - 70 fps.

Draw calls never go past 1400, 90% of the time they are below 1000 .. and im some places drop down to 400...

With high enough frame rates why would i get a lag spike every 5 feet.. (Not exagerating..) And its a big lag spike.. ... often... like second long lag spikes every 5 feet.. or sometimes just from turning the camera... This happens on everything low settings as well..

gtx 580 is a powerful enough card to do a lot.. i mean the worst thing my scene has going for it is overdraw from trees, but im getting these lag spikes indoors as well as outdoors... Its not geometry intensive... the materials are not complex... so... wtf...

Its kinda hard to beleive that a gtx 580 is something that is not powerful enough to run unreal when it runs all modern games fine. Hell my gtx 260 runs most modern games fine... heaven forbid i attempt to use that in unreal engine 4.

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