UE5 PBR Lightning

AlexandrDm

Hi! I've started working on a new environment for my portfolio and encountered a problem with the lighting. Lighting has always been a weak spot in my projects, and I've often heard that it's important to set it physically accurately if the environment is realistic. So, I consulted the Unity cheat sheet and decided to use 10,000 lux and EV10; however, the scene is too dark, and I can barely see the HDRI. Am I missing something?

Celosia

The first thing to do if you didn't already is turn off auto exposure as it makes it extremely hard to judge the lighting intensity. It's so absurdly strong out of the box something lit by a 0.1 cd light can be bright as if lit by sunlight, then you look away and it disappears.

AlexandrDm

Celosia said:

The first thing to do if you didn't already is turn off auto exposure as it makes it extremely hard to judge the lighting intensity. It's so absurdly strong out of the box something lit by a 0.1 cd light can be bright as if lit by sunlight, then you look away and it disappears.

Thanks for the reply! I fixed auto exposure; however, it was still too dark. I looked through the HDRIBackdrop properties and found the Intensity parameter. By default it sat at 1, but increasing it to 1000 gave me the result that I wanted, but I'm not sure if it's the right way to do it. 

ZacD

Yeah the skylight/HDRI strength needs to be relative to the skylight strength, I've heard a ~4:1 ratio is normally suggested, but probably depends a lot on the particular HDRI being used.

Using real world values can sometimes cause artifacts with other features like Lumen having black spots or a grid artifact, I think this is fixed in newer versions, but something to be aware of and look out for. 

Personally I wouldn't suggest going too far outside of the defaults unless you are willing to have to adjust settings for anything that touches lighting and the final image (post processing, sky/volumetric clouds, fog, etc)

gnoop

i am not an Unreal user  but the sun is 100000-130000 lux   as much as I remember.  10k is not enough even for environment  light.    

poopipe

The sun 'is' 120k lux before clouds/atmosphere get involved iirc  - don't quote me but i think the 75k that the sun position plugin provided by Unreal uses  is probably in the right ballpark for actual light hitting earth (i will immediately concede to anyone who has done actual research into this - im doing the sums in my head and im bad at remembering).  

you need to enable "extend luminance range.....  something'  in project settings > render to handle exposure when you start throwing realistic values around or it'll go wrong - badly

It's sort of viable to work with a sun in the 70-120k lux range and a moon at 0.25 lux with lumen but you're going to struggle if you have a day/night cycle that runs relatively quickly and you'll absolutely have to implement some sort of control on your exposure regardless (you might get away with just curve modifications but i wouldnt' count on it, especially if you're running in and out of buildings).   
There's a lot of instability in lumen around sunset/sunrise - particularly in scenes where you have a lot of foliage/grass wobbling in the wind and it seems to worsen when you use very large (realistic) values for your sun. 
None of this is a real issue when rendering stills but it looks like shit in motion. 


personally - i disable lumen for large worlds.  it's not worth the cost / artefacting for large, dynamic environments