Modern URP Lighting Tutorial

[quiet dock]

I've tried baked lighting like a million times in Unity, whether URP, BIRP, HDRP, etc, and it just seems unusable. Even on small scenes it takes hours to render, and then after all that it basically looks the same.

Are there any modern lighting tutorials for URP? Preferably not a video but I guess I'll take what I can get. Most videos skip over a LOT of detail, and it's not clear if it's supposed to take hours to bake lighting on a high end PC in 2025. Things like "Enlighten Realtime GI" being enabled, how does that impact the lighting? I notice no difference with it on or off. Do you have to bake for that to work? What makes it realtime then? Should my lights be set to mixed, realtime, baked? What exactly is the impact of each of those? How do they interact with adaptive probe volumes? How do you get a directional light that you can rotate at runtime, and shadows with nice GI? Static vs nonstatic objects, adaptive probe volumes, there's so much complexity and it's just not clear what's the current "best" approach or modern approach in Unity to get good natural soft lighting in URP these days.

[true garden]

Baked lightmapping is perfectly adequate, and as a system separate from the render pipeline your project is using
Most of these questions would be answered by the documentation, even if it's sparse with little examples

Unity's official tutorials on youtube and Learn have more examples, but aren't quite so comprehensive or modern
Still, it's hasn't changed that much over the years so they are still very useful together with the docs

[quiet dock]

Things like adaptive probe volumes the render pipeline appears to matter, and I'd say that's part of the baked lighting system, though I guess it's independent, but it's unclear to me how exactly it fits in

[true garden]

Do you know what light probes are for?

[long tulip]

It heavily depends on your gpu and complexity of scene

if you don't have higher end hardware baking is just going to take a long time or if you have a very large scene

so long as you set stuff to static and then bake it shouldn't take much more than that to start learning how it works

[true garden]

Assuming they're baking using the GPU

[long tulip]

probably not lol

unless they know about that setting somehow I doubt they changed it

[quiet dock]

GPU baking is default in Unity 6, still takes hours for simple scenes, at least on default settings

I know the general concept of light probes, yes, but not exactly how it fits in with Unity. Tiny thing for example, if you click on the APV object, the component has a button "bake adaptive probes", which actually does impact the lighting. But the lighting window "APV" tab does not have such a button, it seems very odd to me. Why is baking the probes separate? What exactly does baking the APV do, is it positioning the probes, baking the actual light data, both? seems like both. But then what will baking separately do?

there's just SO many settings and concepts re: lighting, and they all appear disjoint but sometimes integrate with each other and sometimes don't. Just want someone to give "here's the best way to set up your lighting in 2025 on URP" sort of guide

FWIW I have a 4070 super, card is fine

[true garden]

You are right about that there are so many settings and concepts, which sometimes relate and sometimes don't

Too many for any one of us to explain really

But if you can show something specific from what you're working with we may be able to give opinions

Like what kind of meshes does your "simple scene" actually have and how big is it

What are your lightmapper settings exactly

What kind of bake performance and lightmap sizes does the summary section at the bottom of the lighting window report

Any errors in console when you baked, etc

[long tulip]

Lighting doesn't really need "set-up" it's built into unity and only requires you mark objects as static, turn on baked lighting, and hit bake. Changing settings is definentally better than the default ones but generally the default should work. Showing your lighting settings would definitely help.

[true garden]

This can produce usable results in some very simple scenarios, but in practice you do need more steps
Forgetting to set lightmap UV generation with sufficient minimum resolution probably trips up the most

[long tulip]

The results you get from default aren't the ones you want obviously but for testing purposes it's more often than not going to produce some sort of visible results you can use as a baseline to figure out where to go and what to change to get the results you want

[true garden]

Setting everything to just "static" is often overkill and because it sets everything to receive GI from lightmaps, produces pretty bad results and long bake times if the meshes aren't suited for it
Setting them to receive GI from probes instead is required in most cases, or excluding them from GI entirely
But the hitch there is that you do need to place light probes and have some idea what they are

And reflection probes by extension, if you want the lighting to be correct

[long tulip]

Again, for testing purposes it's fine and the other options that are included under static won't cause any overt issues

[long tulip]

yeah but reflection probes are for finer lighting adjustments than baking if we're trying to just get lightmapping to work properly and diagnose an issue thats not the concern imo

Obviously these aren't the settings you'd ship with but thats a bit later down the development line you want things to just work first

[true garden]

It's not that uncommon to see someone do the minimum steps and get a bake result with UV overlaps, texel invalidity, light leaking, "fireflies", denoising artifacts, environment noise and maybe even NaN errors all at once
Even if you know what each of those looks like, it may be impossible to decipher visually when the issues overlap

I think light baking is a more tricky subject than most due to this
Issues conflate, and the causes are typically disconnected from the symptoms
Like backfaces in one spot cause invalid texels to appear in a different spot

It's also a burden that debugging those issues requires going through many different parts of the editor, like lightmap view, scene debug views, mesh import settings, environment lighting settings all separate from lighting settings

And that knowing what to do requires a lot of knowledge about the lighting system

If you observe low resolution shadows as an issue, you might think that you'll increase bake resolution or even more cleverly object size in lightmap
But instead of actually solving the issue you would likely blow out the lightmap texture sizes and hit the max atlas size causing potentially comepletely different problems
When the real solution would've been to use and know about Mixed lighting modes

But because mixed lighting is situational and expensive, there's no tutorial or person who can directly tell you to use it unless they know your project also

[quiet dock]

yeah I just can't get it to work well - basically just end up playing with settings, waiting forever for bakes, end up with ugly result, give up. I've shipped multiple games in Unity lol but never can get baked lighting to work well

[true garden]

You have to study the systems involved to be familiar with them, and practice in a scene that's so simple it doesn't take long to bake and which won't give you multiple issues all at once

[quiet dock]

https://youtu.be/K3-wPnhmDi4?si=PnJHmImtdRwh-DSX&t=2590 this is actually pretty much what I was looking for, though not quite as in depth as I was hoping

glad they covered it