Level Streaming FPS drop problem

I have sliced my level into 3 not that big sublevels. I have enemies , enviro lightning and nav mesh on persisting level. Sub levels has only blueprints and graphics.
The problem is that i start on sublevel 1 and when i walk onto stream volume of sublevel 2 i have a FPS drop from 30 pfs to 15 for like 2 seconds. When i walk out of it i have same FPS drop. I Have sublevel 2 config set to initialy loaded and Streaming Usage of Volumebox set to SVB Loading and Visibility.
How can i slowly load other level while walking in a tunnel from one level to another ?

Hello Dziobson,

I have a few questions for you that will help narrow down what issue it is that you are experiencing.

Quick questions:

  1. Can you reproduce this issue in a clean project?
  2. If so, could you provide a detailed list of steps to reproduce this issue on our end?
  3. Could you provide screen shots of any blueprints that may be involved in this issue?

I just have 2 sublevels on my persistent level. Both have some graphic on it, like dungeon or something. And When i walk through tunnel between one level and another (which is on persistent level) I Load level and change it visibility to be visible, and in same time I unload previous level. Then I have FPS spike.And it always appear when i do Load sublevel. But if both levels are always loaded and the only thing i do is to set visibility to true or false. There is no Spike then. That’s why i had to make a doorway in the tunnel. Black screen and Load sublevel then (Like in skyrim for example) So there wont be any spike.

( I Posted the problem :slight_smile: )

Hello Mariusss,

Thank you for the information provided, however could you please answer the questions that I asked of Dziobson?

Ok… ill do so. And then replay

Hello Mariusss,

We have not heard back from you in a few days, so we are marking this post as Resolved for tracking purposes. If you are still experiencing the issue you reported, please respond to this message with additional information and we will offer further assistance.

Thank you.

I have the same problem. When streaming load/unload (especially unload), GPU time has a spike, and the frame rate drops a lot. It significantly affects screen scroll animation on mobile devices. use Stat Unitgraph command can see the spike. This problem becomes more noticeable when a sub-level has higher complexity. My sub-levels have foliage and landscapes.

I suppose that streaming load/unload is on a different thread and should not block the main thread.

Hello Li,

Thank you for the information provided, however could you please answer the questions that I asked of Dziobson?


  1. Yes I can reproduce this in a clean project
  2. Steps to produce:
    • Use blueprint streaming to load and unload sub-levels
    • use stat unitgraph to monitor GPU performance
    • Whenever you unload a sub-level, a spike happens on the graph
    • The more complex your sub-level is, the higher the spike is
    • On mobile device, there is a noticeable lag when unload
  3. I can provide a really simple project. Since the sub-levels are really simple. the spikes are small. Can’t upload here because of the size. Please let me know when I can send it.

There are a bunch of requests from other developers here:

Thank you!

After doing a bit more digging I found that this is a know issue, I have provided a link to the public tracker. Please feel free to use the link provided for future updates. Thank you for your time and information.

Link: Unreal Engine Issues and Bug Tracker (UE-10109)

Make it a great day