Is lumen really optimized for games?

salimmatta

Hey guys,

I have been working on my game since a year ago, as I have started to do the lighting in the scene, I have noticed that whenever I select the lights to be static and bake, they simply disappear from the scene. So I guess the lumen does not support bake lighting. This leaves me to assign all lights (mainly rect lights)  to "Stationary".

But the question remains, is it really optimized for games?

Thank you,

Fabi_G

The Lumen documentation states it's a "fully dynamic global illumination and reflections system that is designed for next-generation (current gen now) consoles" - so no baked lighting with Lumen. If you want to use baked lighting you would have to setup your project accordingly.

The question whether Lumen is optimized for games is one too general. What type of game on what platform? As far I know Fortnite can be played with Nanite and Lumen enabled - if one has the hardware.

rexo12

Using entirely stationary/dynamic lights is not that unusual for a game, and hasn't been for a while. Open-world games practically require it.

I think lumen is probably a bit immature at the moment, Fortnite notwithstanding with first-party support from Epic. However given the typical development cycle time I absolutely do expect games in the next few years to employ the technology, or other studios to develop their own implementations (EA was playing around with surfels, for example). Epics vision for it probably also relies on wider use of technologies like TSR.

 All things considered getting fully dynamic GI for 2-4ms on modern hardware is a pretty sweet deal and totally workable.

salimmatta

Fabi_G said:

The Lumen documentation states it's a "fully dynamic global illumination and reflections system that is designed for next-generation (current gen now) consoles" - so no baked lighting with Lumen. If you want to use baked lighting you would have to setup your project accordingly.

The question whether Lumen is optimized for games is one too general. What type of game on what platform? As far I know Fortnite can be played with Nanite and Lumen enabled - if one has the hardware.

Thanks for the reply, well I have completely forgotten than fortnite can run fully on nanite and lumen, however my game is a metroidvania (3D assets with a 2.5D camera setup) so i suppose I'm safe, if fornite is doing it.

Alex_J

well fortnite has the epic team behind it so they have a bit more firepower than a solo-developer. but it looks like you can include lumen in quality settings for your game:

https://docs.unrealengine.com/5.2/en-US/lumen-performance-guide-for-unreal-engine/

the game user settings has a benchmark node that you can run to detect user hardware, I dunno if it is updated for lumen or not though. I haven't read through that guide carefully but it looks like if lumen can be tied to quality tiers then it should get automatically adjusted by the benchmark nodes recommended settings.

https://www.youtube.com/watch?v=Czp4g3AFP_k

rexo12

@Alex_J I wonder how well this works in practice. Losing GI in a scene originally designed and lit for it would have a very significant impact visually, I feel like you'd need 2 different lighting scenarios for lumen on and lumen off. I almost feel that I wouldn't even bother with trying to support both.

Unreals current default scalability setup does disable lumen at Medium settings I believe.

Alex_J

yeah I have thought about maybe if i wanted to target low end, perhaps just design without lumen from the beginning. but havent done any real performance testing for it.

poopipe

if it's any help 

i just took an in-editor capture  at high settings, approx 2560x1440 resolution with lumen, UDS and a load of trees
this was done on a 3080



0.36 ms is more than acceptable on a 12.8ms frame - I'm pretty sure  SSGI would be higher (tbf that's a fixed cost, I expect this to get worse with more content)

this isn't particularly scientific:
I can't remember what I've done with lumen settings, I only have the UDS sun and moon directional lights and I only have about 2x2km of my level loaded