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FPS drop on camera rotation


I'm having a strange issue where some players are experiencing an FPS drop when rotating the in-game camera.

  • The FPS Drops only when moving the mouse

  • Lowering graphics have no effect and the issue remains as before

  • when the camera is stationary, everything works correctly.

View of issue: https://youtu.be/-1UjdBo5c24

The camera setup is simple and outlined below:

alt text

I cannot replicate this issue on my end and its specific to a handful of players. After some research, I was able to improve the FPS drop by turning off V-Sync but the FPS still wasn't optimal.

Has anyone experiences this issue or have an idea on how I can solve this?

Thank you :)

Product Version: UE 4.21
image-1055.png (90.3 kB)
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asked Feb 21 '19 at 02:46 PM in Blueprint Scripting

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2 answers: sort voted first

I think that the problem is coming from the fact that you are not multiplying your input values by the World Delta Time at all. That would explain the jittery-ness of the video, and why you can't replicate it on your machine.

The node you are looking for would be "Get World Delta Seconds", and then you probably want to add a "Rotation Speed" variable or something and multiply by that.

Here is a snip from the FPS Blueprint template:


fps-bp.png (158.5 kB)
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answered Feb 21 '19 at 04:13 PM

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avatar image krishcrush_ Feb 21 '19 at 05:28 PM

Thank you :)

avatar image krishcrush_ Mar 08 '19 at 11:50 AM

Hello - looks like this didn't solve the problem :(

The frame drop still exists when moving the mouse. Dropping the graphics settings seem to have no effect.

Any idea what else could be causing this issue?

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The FPS may depend on what is in your viewport... what you are rendering...

For example, in my current project scene, if I point my camera at the ground the framerate increases. If I point it at an area with a lot of transparency (causing overdraw I think) the framerate drops. You can use the console command "Stat UnitGraph" to see whether your GPU or CPU is causing the framerate drop. Whether you are GPU or CPU bound. Zak Parrish of Epic did a great introductory performance profiling video on the official Epic channel about two years ago.

Also, make sure Google Chrome and other apps aren't running in the background... Netflix causes a heartbeat like flutter in FPS (you'll see this if it happens by using "Stat Unitgraph"... the heartbeat pattern of interference from another app is blatantly obvious)

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answered Mar 09 '19 at 01:36 PM

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avatar image krishcrush_ Mar 09 '19 at 02:44 PM

Thanks aNorthStar - maybe I should have clarified. This issue is limited to a handful of players and they are running high-end machines. The FPS does not drop if the mouse is stationary (on any part of the screen). It it only when the view is rotated / mouse is moved that the FPS drops.

avatar image aNorthStar Mar 10 '19 at 06:19 AM

honestly, I'm not sure... a few things I might try:

  • turn on/off VSync

  • turn on/off mouse smoothing

  • ensure the machines are only running your build and no other apps (yes it matters sometimes, even google chrome as I mentioned above)

  • use performance profiling on the specific machines to see where the stuttering is coming from

  • check that controllers are consistent (all using mouse, joystick, etc)

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