Question about light intensity in HDRP

In HDRP, the unit of light intensity for a directional light is "lux". According to Wikipedia, lux is defined as "one lumen per square metre". Examples measurements of lux in different circumstances:



When creating a new scene in Unity in HDRP, the directional light intensity is set to PI (3.141593), which according to this table equals something like civil twilight.

The sample scene in HDRP has a directional light with an intensity of 10, which is something between civil twilight and "public areas with dark surroundings".

The FPS sample project has a directional light source of 1,000 lux, which equals an overcast day/TV studio lighting. The entire scene is actually completely white unless a strong auto exposure is used.

None of these are even close to the true lux of sunlight. When trying to use a realistic value, the scene becomes so bright that even with maxed out auto exposure settings, it's essentially just white.

My questions is this:
Why these intensity values?

All these values (3.14, 10, 1000) are not physically accurate and seem rather arbitrary. If just taken out of thin air, why 1000 and auto exposure settings for that value rather than 10 and auto exposure settings for it? Is there any guide or best practices regarding lighting in HDRP? It all seems so confusing and arbitrary from the examples I've seen.

 

Wait for the upcoming HD Postprocessing which will implement physical camera properties. You will be able to use proper lux values with proper exposure settings.

 

Awesome! Where can I read more about this?

 

Nowhere yet, but you can download this experimental postfx branch https://github.com/Unity-Technologies/ScriptableRenderPipeline/tree/hdrp-postfx

 

They had to use workarounds for FPS sample so you're not alone in wanting this

 

Wow I didnt realise that and had been scratching my head a bit on this, thanks!

 

It's in my breakdown on the FPS sample forum and Unity explained the rationale.

 

https://forum.unity.com/threads/tho...ple-project-feedback-on-content-design.574549

 

Oops sorry forgot link (thank you).

 

Hi @seb

Hello!

Ehm... Why don't you hide this Lux drop-down then? Or show a warning or something? This feels carelessly right now...

 

This isn't a problem. Everything is setup properly now since 2019.1 and HDRP 5.x.x
Everything above was an issue late 2018

 

I see. I faced this problem using Unity 2019.1.12 and HDRP 5.x.x.

 

Quick way - Not physically accurate but works
- Set the Sky Exposure to 1
- Set the "Scene" Exposure to 1 as well
- Lights will have to be adjusted accordingly
Everything should render as you are used to in the Builtin Render Pipeline or LWRP. Note using it this way you are in charge of calculating your own light intensities instead of using physical values.


Physically Correct or In that General Space
- Open the Render Pipeline Wizzard and let it set up the defaults for you. Window -> Analysis -> Render Pipeline Wizzard in 2019.3 and HDRP 7.x.x This is in Window -> HD Render Pipeline Wizzard Select Fix All
- Create a new scene and you should get a default scene with a lighting setup (The Lighting there isn't physically accurate but it gets you setup)
- Change the values to whatever needed depending on the scene.


Useful Links
HDRP Docs on Physical Light Intensities
https://docs.unity3d.com/Packages/c...finition@6.9/manual/Physical-Light-Units.html

For the Sun/Directional light
https://en.wikipedia.org/wiki/Daylight

For the HDRI Sky or Physical Sky
https://en.wikipedia.org/wiki/Exposure_value (Scroll down to the Chart Labeled Lighting Condition)

For the Exposure/Scene Exposure
- If you set it to Fixed then use the same value as the Sky EV/Exposure Value
- If it's set to Automatic then set the Limit Max to the Sky EV and the Limit min to the brightest you want the darkest area in your scene to be. (If you aren't sure yet leave it at default)

With all that done you have fairly physically accurate lighting.

 

Hi everyone,

I am new to unity. I am an architect and I am using unity to conduct a research experiment. I need to evaluate the lighting level on a surface now that I have set up my scene. Does anyone have any idea how I can do that?
I am not using HDRP but I realize it works with physical light values, should I switch to that?

I need lux values or values that I can rely on to translate them into lux.
I will be grateful if anyone could help me

 

Yes, you would have to switch. HDRP is the only renderer for Unity that uses physical light values.
- Lux (for Directional Light/Sun/Moon)
- Lux, Lumens, Candela, Ev 100 (for Point/Spot Lights)
- Lumens, Ev 100, Nits (for Area Lights)

Have a look at these guides

Docs
Physical Light Units and Intensities - https://docs.unity3d.com/Packages/c...finition@7.1/manual/Physical-Light-Units.html

Blog Post
How to set up Unity’s High Definition Render Pipeline for high-end visualizations -
https://blogs.unity3d.com/2020/01/0...-render-pipeline-for-high-end-visualizations/

 

I also recommend URP if you want to target general mobile devices such as working in the field with an ipad or something.

Both pipelines are PBR and backed up with shadergraph. HDRP is very high end presentation with raytracing support (new nvidia cards only) and URP will run on anything..

Both happily support PBR and baked lighting though.

 

Oh! Thanks a lot for your help and reply.
Does it allow measuring the lighting intensity of a combination of lights in an area as well?

 

so i recently upgraded from 2019 to 2020, and i noticed my Sun has a cool new preset slider. except anything above ALL THE WAY DOWN, is completely blown out white. im obviously assuming, for good reason, that my project has been corrupted. the only way i get good lighting previously, was just to eyeball the anything-but-lux settings myself and artistically choose what looks good.

but this super cool, new and helpful (AKA completely worthless) slider has my attention. should i just ignore this like everything else? or USE IT? i need help. i cant figure out why a cloudy overcast setting has my scene completely WHITE, unless i ruin all of my exposure settings? is that DESIGNED to happen? or is my project BORKED.

any help would be much appreciated. thank you.


EDIT:
ADDITIONAL QUESTION:

in all honesty, what is with the weird CG world attempt of realistic settings like lux and kelvin. i never understood in decades ago when 3ds max tried implementing it. real numbers never match or look good, and just waste your time. give me an easy to use SLIDER from 0 to 100 or even 1000, and get out of my way. why am i fumbling with BS lux settings which have NO weight whatsoever in the CG world, and now trying to balance it out with exposure? is this a CAMERA? nope. its a screen and a CPU.

so heres my question, is there any benefit from all of this? and i dont mean trying to cheat by copying light bulb settings, not sure why id need to do that anyway, im an artist after all. arent you? of course you are. why else would you be here.

is there any REAL benefit? does cranking everything up, just to level it back out again make the highlights look better? or normal mapping? there has to be something. if not, why bother. just a waste of time. like this post.

 

I am just so confused right now ... I have absolutely no idea how to set the values.
Using the HDRI Sky seems to change everything because the sky itself has a multiplier, meaning the "default value" or the amount of lightning it should contribute to the scene is with a multiplier of 1.
Turning up the Directional Light to ~100k lux and the exposure accordingly makes the HDRI sky just black (with a multiplier of 1)

I adjusted the value of the HDRI sky, so it is visible but noticed some problems with the additional shaders that come with HDRP example files, such as LitDistrotion - this thing is just pure white with the high value setting (sun at 100k lux).

Now reading this thread, which goes from "not possible, use wrong values" to "this works now" - I still feel like everything I set is just wrong.

Downloaded some HDRP Model Assets recently and they use a directional light value of ~20 lux, after building some levels with the asset, I noticed that all emissive spots are completely missing, the only way to make them visible again, even in areas within shadow, is to reduce the exposure-scale of the emissive texture slot (in the hdrp lit material) to 0, so it is not affected by the very high exposure.

All other lights do not match either, I googled up some light bulbs and set their values - they are just invisible with this HDRI Sky & Directional Light Setup. So something has to be really wrong here.

Because we need the distrotion shader and because everyone else seems to use just wrong values and makes their assets like this, I think I will change the Sun to 20 and the HDRI back to a multiplier of 1, with auto exposure around -2 to 2.

But if anyone has some advice on this, I'd be very happy.
And please, unity, give us some hints on how to set the values, somewhere in the docs - a full setup of HDRI Sky, Exposure, Directional Light and some indoor area with artificial light sources on one page - or a proper example with these level-areas and lights (in one scene).

 

My $.02: Well, if you want to follow Unity's recommendation, just open up the new default scene. They have set up a complete scene where they showcase an open "room", a semi-open room and a completely closed room. You can study the lighting setup right in the editor and you can bring in your assets and you can test them how they look in an officially lit scene.
https://blogs.unity3d.com/2021/01/07/explore-learn-and-create-with-the-new-hdrp-scene-template/

 

If you have a lighting in video/photography background already then lighting in HDRP already comes pretty naturally.

But for those who are transitioning or honestly new to how lights work then this unity in-depth has a great segment on exposure plus other quality fundamentals that are worth studying up on if it's not your particular field.

It's worth noting too that it's perfectly fine to rely on another's skills and knowledge, Swiss army people in this industry are extremely rare.

Keep it up all.

 

I've watched the whole thing twice, first time when I installed HDRP and we got strange results.
Second time after a few months, where I tried to do some lightmapping.
Still have no idea, as the Shader "Shader Graphs/ParticleUnlitDistortion" (which comes as an additional package to HDRP, right in the PackageManager and was not modified by me) is just pure white.
We need the effect for some cool heat & shockwave effects, so I tweaked the lightning, so the shader works.

Also why would I use a HDRI Sky Multiplier of something else than 1 ? "One" seems like a default value for a multiplier?
And if I set it to "One", the directional light to something around 10, the shader works perfectly, exposure is around 0 (which to someone not knowing anything about photography seems like the default value too - I know already it should be something like 12-14 or so) and it works.

Personally, I don't care if real values are used, I just want to make a game, not any kind of real life simulation, so I'll stay with these low, unrealistic values. I can't even see any difference in the scene itself, to me, it looks exactly the same. oO

 

Then you don't need HDRP.

 

URP has quite a limited feature set - is SSAO even added at this point? What about contact shadows, micro shadows, Decals, SSR, ...
Standard Pipeline has no shader graph and is missing a lot of other features too - when working on a game with an realistic artstyle, HDRP seems like the correct choice, even if it's not an architecture visualization or a car-advertisement demo.

"Need" is subjective, no one really "needs" good graphics

Also it was stated nowhere that HDRP can't or shouldn't be used for games - I'd just like to know if the shader ("Shader Graphs/ParticleUnlitDistortion") has issues or if these are actually the values that should be set, when using the HDRP for a game project.
The shader itself is pretty basic, it just takes the scene color and moves the pixels around but when the scene color is pure white to a shader, idk ... it seems wrong to me.

 

Your choice of HDRP or URP has *nothing* to with realism. Both are capable of near-ground truth physically based shading.

Instead your choice of pipeline is 100% only and ever only, to do with your target hardware if it is applicable. The fact is nobody is deploying HDRP games to switch or mobile or even VR if they have any sense, and a large amount will still pick URP for console games, purely because they want to PORT it without any issues.

So you pick your pipeline based on where your product is intended to go, not based on the final pixel quality, since the fact is HDRP simply isn't going to go to a lot of places, while URP will.

 

Simple: the target hardware you intend to deploy on can handle HDRP AND you want to use the features HDRP offers: you use HDRP, if any or both of these aren't satisfied, you go back to the available choices and choose a more suitable one.
I got the impression that you don't really care about HDRP feature set, so I advised you don't need it. You can create arbitrary good looking stuff in URP or in built-in renderers too. HDRP's most strength comes from the nature of the values you can set in them: they can be physically accurate initially (then you can make the artistic choice to change them, but that's another question). Up until the point of my answer you haven't mentioned a single HDRP feature you care about, you only told us that you don't care about physically based setup.

There is no "correct choice" if you don't know what you're doing and what you're choosing and what you're choosing from.

 

Right now it's far too late to think about this decision, the project started almost one year ago, somewhere end of April 2020, we have a big beautiful world with lots of details that shine thanks to micro shadows and other features.

Yes, I didn't talk a lot about the feature set at all because, this post is not about choosing a render pipeline for a project but rather understanding why a shader that comes with the pipeline itself, simply doesn't work when using real life values. And why every asset developer seems to use low values too. And why the HDRI Sky multiplier of "1" is not a default value (when using exposure of ~13).

As said, the shader works with a setup where the HDRI Sky multiplier is set to 1 and the light is tweaked accordingly (somewhere around 10).
Thats quite strange and to me, it seems like this is the setup for anyone who wants to use these kind of particle shaders = to anyone who wants to make a game.

Sorry if I was quite defensive or offensive? idk, wasn't ment to offend anyone ^^ I am grateful for every answer I get as theres always some valuable information. ^^

 

I actually think HDRP's strength is the fact it's all realtime and raytracing only adds to that.

While on URP you can get an identical looking scene but it's all going to be baked right down.

 

Hey thanks for getting back.

Sorry that i dont have an answer to all of this, but the fundementals you mention at the end real value vs fake values = same results, it's just mostly to do with a baseline achor point for you and teams.

it's not that you HAVE to use real values, it just makes it easier if you use more complex lights or decoupled systems ( like clouds for example).

if you do set a baseline for realistic values then put your systems with lighting involved ( other lights clouds, FX, Bloom, volumetrics) you can use measured values to aid getting the look you're aiming for and actually know what those values are in many cases.
When it comes to rendering and baking you'll know what to expect in return also and wont be surprised by something crazy going on.


If you have an lighting art or film director ask you to drop a scene by 1 ev to match their reference ideas you wouldnt really know how at this point if you didnt already set a baseline.

You could arguably also consider this very similar to how 'Units' are set in game. unity units are agnostic so its completely up to you how you set your units and then send you art team then info for Uvs texals and modling scalem unit = mm cm m km etc etc.

This lighting concept would be the same. set your lighting baseline accordingly and send the " baseline unit" to your lighting team so they know the measurements they're working with. and if they have to convert said measurements, they can.


In any instance as you're defining your project outlines and framework these are some good guidposts to help to decide and unify end render goals for you and your team.

Hope that helps some

 

I chose HDRP because I needed volumetric light, and also I did not want to be surprised that I'm not able to have some feature later in production.
I'm aiming at desktop/console.

 

I see, what you are saying, however it is still super-weird to me that you're ready to throw away your entire reference-system for one shader. Instead of finding out what's wrong with it. Not to mention that distortion is an effect, which can be recreated even in VFX Graph.

I'm not big on shaders, especially not with particles, so probably won't be able to help too much. My advice is to try to get help here. @richardkettlewell is a great guy, friendly and helps forum-people very often. And if I'm not mistaken he wrote these shaders too, he may be able to find out what's wrong in your case.

 

Well, I am confused, thats the issue xD

Lets define what I mean when I say "real world lightning". This basically means a directional light set to a value of around 100.000 and the exposure set to ~13

And unrealistic / low values / fake lightning means the directional light set to ~10, exposure around 0.

1) HDRI Sky can be set to "multiplier" and I would assume that "1" is a default value for such a multiplier. Well, "1" as value makes the sky basically black when setting the scene to real world lightning.

2) When I set the light to real world lightning values, the shader is pure white.

3) Assets from AssetDevelopers on the store come with example scenes using unrealistic light values. Taking those assets and putting them in a scene, set to realistic lightning values, a lot of readjustment is needed. Adjusting Emissive Intensity in every material and adjusting every light thats inside a prefab of the asset.

And all three of them work fine with low, unrealistic values for the lightning. Therefor my assumption: low unrealistic values are the go-to for GAME Projects, while real world lightning is meant for OTHER Projects, such as Film, ArchVis, Static Renderings, Car Advertisements, Render Demos, ...

BUT this is not mentioned in the docs.
Actually when reading the UnityBlog and some Threads on the forum - there are posts where Unity Devs say, that realistic values just don't work and some where they say that realistic values should be used because thats how the HDRP works and was designed for.

And by the way, your shader is awesome! (when used with unrealistic lightning values) ^^

 

Hey its not that bad
It only took us around 6 months to be 70% sure about being correct on our light setup

 

So what is your secret ?
Recently I again reached the lighting problem.
To be more precise I wanted to dim the scene in linear fashion from lit to complete darkness.
My directional light is 100000 lux it affects ambient light, but the ambient starts to get dimmer around 0.5 lux.

 

Does anyone know if there's a way to read these values at runtime?