I’d appreciate it if we get a reply here what’s the plan regarding implementing physically based units for lights.
Is it being considered at all?
Property system does not support units, so if anything it needs to be done via functions. There possibility that light properties is already based on those units (same as 1 position unit = 1cm supposly), but i’m not sure. Changing units used in specific properties now would create massive backward compatibility problems preventing people from upgradeing there projects to new UE4 versions. So conversion functions if property not already based on those units is only option here .
Well in nature making improvements causes some troubles along the way but it’s like saying making the rendering system physically based causes the traditional texturing workflow to don’t work anymore. It’s necessary change. Any change towards achieving more physically based elements is really necessary in my opinion than worrying about causing compatibility issues.
Lights already use lumens as the unit. Though the ones that don’t I’m not sure what it’s based off of. Internally I’m sure all lighting is based off physical units.
Point lights and spot lights only support Lumens.
Directional light doesn’t have a unit, meaning the Sun (the most important light source in every project) is not physically accurate which is a big deal.
Personally I think there should be a drop down at least to allow use Lux or other things while others who don’t want to change their lighting can keep it the way it is.
Would like a feature request ticket for this since it’s not on the new roadmap anymore. 
I’d like to see this too. It is still possible to get good results, but it would be nice to be confident in the values we choose. 
please do it.
I created this thread back in 2015 asking for physical units for directional light.
Just saw <this>right now which is awesome.
But still, it’s been 2 years of wait and this engine is probably the only one that still relies on artistic guesses for making environments look realistic instead of relying on real world values. And guesses are never correct.
The point of PBR was to replicate both real world material properties and real world light intensities and achieve true realism by mixing the two. But without real world light values we’re still far from “correct” and we still haven’t achieved the true meaning of “PBR materials looking correct under all lighting conditions” because our light isn’t based on real world values.
Can we please finally have a physical value for directional light? this was in fact removed from the roadmap months ago when the roadmap go redesigned. But well, this is pretty important and needed feature.
Looks like it’s already on the roadmap for 4.19…
Nope it’s not. Read the card description. Nothing about directional light.
And casting random amount of light on game world is really bad practice.
Well well well, what do we have here?
That’s only for Point and Spot lights. Directional Light has the most effect on game world and should be physically based. That’s basically what I’ve been asking for.
Hi, 4.19 will have physically based units for point lights, spot lights and camera exposure. For directional lights, their intensities was already exposed in lux, so they are unchanged.
Hi, It’s not in Lux. It’s just a brightness multiplier without any units. Said RyanB.
Lux values are actually quite huge numbers i.e Sunny day: 100,000 Lux. If you enter that number as directional light intensity… that’s not going to work as it should.
Hallelujah! I’ve been waiting for this for a long time. I’m going to second the request that we get proper units for directional lights though. That’s arguably the most important one to get right.
Hello.
I’m waiting also for the same thing… Unit for the Directional light. For a PBR workflow, it will be more accurate than just tweaking with eyes… So please, add unit (real) for directional light!