Hey guys, and engineers at EPIC, I am wondering why the latest iteration of Unreal Engine are scaling so terribly with resolution. In a tiny tiny room, with a superclocked Geforce 980ti, I go from well over 200 fps at 1080p, to 125 in 1440p down to a whopping 49 frames per second in 4K UHD. Why is it like this? I love this engine and everything about it, but I hate the resolution scaling performance.
I will also add tree comparison screenshots taken of the same little blue room at the different resolutions:
Thanks for an amazing engine none the less! Bless!
UE4 uses deferred rendering, wich means that its pixel shader usage its quite high.
Each light calculates its light formulas once per pixel(normally), so when you get to 4k, pixel shader gets hammered 4 times more than in 1080p, while cpu and vertex shader stay equal.
That x4 difference checks out. Specially in such a simple scene, the vertex shader load and cpu load its negiglible, all the load its on the pixel shader, wich cuadruples in 4k.
Exactly. The post process effects also play into your performance loss, the simple fact of life is you want to support 4k resolutions right now you have three options. Take the hit on performance and render at 4k, start disabling effects until you get the performance you want, or render the world in 1080p and render the UI at 4k. I don’t know what it would take to get UE4 to do the latter but that’s what I would do. Fact is most people aren’t going to notice you rendering at lower res as long as the UI elements are rendered at full res.
