Scene Capture Cube & Deferred Lighting performance:
Ultra bad performance in the Reflections 24-30FPS demo map from the Content Examples.
24-30FPS with:
GPU 780GTX 3G VRam DX11
16G Ram
CPU i7 4770K 3.5Ghz
1.6 - Scene Capture Cube (Dynamic) - in killing the performance (eat all FPS)
*Without Dynamic shadows + Deferred Light this give 90-100FPS
The deferred lighting over here have super bad optimization.
Deferred Lighting Off = ~95 FPS
Deferred Lighting On = ~26 FPS
~70 FPS of difference with 5 lights in the scene…
I am uncertain exactly what you mean by Deferred Lighting, but I am assuming that you are referring to changing the lighting mobility from the Stationary to Static which again would be expected to yield the same performance cost you mention above. Since Stationary lights in the immediate area of the camera frustum function as dynamic lights and with such a small map the stationary light cost would be nearly equal to having fully dynamic lights in the level, so moving to Static I would expect a large increase in performance, https://docs.unrealengine.com/latest/INT/Engine/Rendering/LightingAndShadows/LightMobility/index.html
Ah, the Show Flags, I always forget about those options. This behavior is actually expected as well though. You are removing the dynamic lighting elements from the Cubemap generation process (essentially removing an entire render pass) so I would expect a large performance increase. This would be a great setting if you were using a Dynamic SceneCapture to get reflections on water or large glass surfaces and don’t want to add to the Specular nature of the surface.
Select the camera of the scene capture, then in the properties → Scene Capture → Advanced Show flags → Deferred Lighting turn on/off
*And the shadows is a other flag.
The cost is expected, but if you turn all on except the Deferred Lighting you get 95-100 FPS and with Deferred Lighting 24-30 and that don’t is expected, you can’t use this in a game then, with only 5 light on a small cube scene you get 25 FPS.
We in part some of this FPS information is completely Hardware based as on my CPU I am looking at an average 30 to 40 FPS with the average being around 31 when looking directly at the Sphere object in the Reflection Map. As the documentation linked earlier says, this dynamic generation is incredible performance intensive and should be used in limited settings where the effect cannot be achieved any other way or as an option for individuals running very powerful GPUs and even then in confined areas.
As you have noted, the correct way to use this feature for better performance is to remove the deferred light pass which removes an entire rendering pass and will give you a significant performance increase.