UE4 performance - viewport drain


Attempting to output a double-wide 1920x1080 (so 3840x1080) render target from UE4 and split it between two projectors in LA – got it working, but it dropped our fps from ~90+ to ~10fps.

One thing I noticed was because our player controller is still outputting to the UE4 viewport, it’s functionally rendering a 1920x1080 and the 3840x1080 views at the same time… is there any way to turn off the main UE4 viewport render for the player?? With the Scenecapture2D output going to LA, we don’t need to have UE4 outputting a separate view of the player camera to the viewport…

I assume there’s no way to send the player camera to LA from UE since render targets are exclusively mentioned in the tutorials? Also was beginning to attempt two 1920x1080 SceneCapture2D’s to output to each projector, but figured that was likely even less performant…




Hmm, that sounds like a very big FPS drop indeed. It makes me think the reason might be somewhere else, but I’m not sure obviously. Does the performance drop happen also if you are not actually sending Spout out? Just using Scene Capture with render target? Also, what’s your VRAM usage?

Just as a comparison, we ran this scene on NVidia P6000, 32GB, Intel Xeon Gold 6126. I don’t remember the exact framerate, but it definitely didn’t drop that much. We used Scene capture component with a Render target with 4K resolution (3184x2160).

To your questions: I wouldn’t consider myself a UE4 expert and you might be better off asking this in UE4 forums, but afaik there is no way to ‘disable rendering’ as such. You might be able to do the same thing to play with the settings of the active camera. Alternatively, if you are using a packaged or standalone game, you will decrease the performance cost of viewport rendering by decreasing its resolution. There is a console command for that (I think it’s something like r.SetRes 640x480, but you should check that).

Lastly, UE4 has very good profiling tools that might help you pinpoint the biggest load.

Let me know what you find out.

Good luck!