Random FPS issues with a specific part of map?

We’ve got an ongoing issue on one of our maps (MOBA-style) where the camera stutters and there’s huge FPS drops when hovering over a certain part of that map. My programmer has written up a description of what he’s found but we’re unable to make sense of it. Hoping that someone else has had some experience with it and may know the fix. Here’s his write-up:

"I did find something. I belive it might be related to the camera jitteriness too. I tried recording, but Bandicam drops my frames to the point you can’t even notice the difference. However, try Stat FPS and then move your camera north and south. If you stay anywhere past the center of the Circuitball, for me at least, frames are consistent at around 120. If you move south of the center, the frames start dropping. From the center to the edge of the map, my FPS dropped by 30 frames. I removed everything from the map, and it happens even when the map has absolutely nothing but the landscape.

I don’t think its the landscape itself though, because the landscape is about the same north and south, if anything, the north has more bumps and stuff that would cause a drop but don’t. After some more investigation, everything south of the center is in the negative world X value. So I tried to move everything north of that, but the problem still happens at exactly south of the center of the map. So, not entirely sure what causes that, but I think it might be something with the landscape itself perhaps. The issue doesn’t happen in Standoff. It might also be the starting the position of the camera, because the camera does in the center of the map, so perhaps moving south of its original position causes an issue. I feel if its not the landscape, maybe its connected to our camera itself, and maybe even the camera stuttering. Like our camera has issues moving into a negative X from its starting position. Not the Y though, left and right did nothing, only south."

Any ideas on something like this?


Look into the Profiler: Profiler Tool Reference | Unreal Engine Documentation

It can tell you what is taking up the render time

Test one, flip the map and see if hovering in the same direction has the same FPS drop.
If it doesn’t then issue is not the map but something else.

Test 2, Disable the landscape material (copy the map to a copy, then create new layer blend files for the copy and apply them to the landscape paint layers. Or just use a new black material with literally just 1 base color as if you were restarting the map from scratch).
If the issue persists something is up with the material layers (or combination thereof) utilized within the section that drops FPS.

Test 3, remove every part in the map/lrvel copy until you find the culprit. Actually delete it since you have the original one to go back to you dont have to disable from view…

Other possible issues: size of the map? If you are dealing with 20k plus you may have some drops in FPS while calculations are being performed (any material that uses world coordinates for instance might have a longer time to compute because of the floating point precision issues). It wouldn’t really justify the drop from 120 to 30 you are nothing though. At least I have never had it that bad.

Like Viper said the profiler would help figure out what to disable / what the bottleneck is.