Rendering Millions of Dynamic Lights in Real-Time

[OCASM]

Here’s another example of ReSTIR in action:

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

@Murgilod

So what we’re circling back to is you having no idea what you’re talking about. The reason it’s inferior is because of several reasons, again, none of them technical.

• Poor lighting setup. Generally speaking, three-point lighting in games is set far too wide while also far too close, this leads to poor contrast on facial features that makes them look often washed out and flat
• Games have to account for lighting in a variety of different conditions. Three-point lighting suffers if you use the same configuration without regard for natural light levels. This manifests heavily in the Horizon games where often the three-point config is trying to work against the natural light direction like from the sun
• Surface and subsurface shaders are only ever an approximation and need to be lit with care to account for that

You’ll notice that none of these problems are technical limitations and are, instead, limitations that come from applying the setup incorrectly or not knowing when the setup should be disregarded in the first place. These are also things I covered when I pointed out how your Star Wars comparison was utterly meaningless.

Can current games have three point light setups (or any other setup) with area lighting/shadows? No. It’s that simple.

@Murgilod

Having loads of shadow casters is another one of these things where it’s pretty clear you’ve not spent a lot of time studying how light behaves in film or reality. When you have enough lights in a scene, shadows start to become muddied, indistinct. You can see this in films that are set in places like exteriors in Las Vegas or downtown New York and you can also see this for yourself in those places. The more shadow casters you have, the less distinct shadows are, but also you’ll find that you rarely have more than two dominant shadow casters to begin with.

This is true in real life too! You’ll either have shadows cast by the sun or the brightest light/lights in a room. Light fixtures with multiple lights (to the surprise of nobody) will generally cast a single dominant shadow. If you need that to be more accurate, there are ways around that that don’t rely on this tech.

Having millions of dynamic shadow casters is, again, not something that has much practical benefit for even the AAA space.

You assume, wrongly, again, that millions of shadow casting lights = millions of shadow casting discreete point lights. Area/emissive lights are approximated by using thousands/millions of lights.

@Murgilod

You mean extremely low intensity lights that any deferred renderer could handle with ease but you’d be better off just using emissives and maybe GI anyway because the shadow casting range is maybe only a handful of inches? And, in the case of lights with a diffuse coating to them, don’t even do that much?

You’re falling in to a common issue that a lot of people in tech do: they see something neat, maybe an algorithm or a new implementation of something, or a new piece of kit, and then they spend the next while trying to apply that as a solution to problems that don’t really exist, often blowing things out of proportion in an attempt to make it seem like there’s a problem in the first place.

The problem here is that you’re attacking tech that you don’t even understand what it does. Allow me to help you with that:

https://www.youtube.com/watch?v=QWsfohf0Bqk

(This one includes shadowed christmas lights)

https://www.youtube.com/watch?v=56tkm95gfFI

@neoshaman

Imma gonna said Murgilod is spot on, you ought to listen to her!

While we have some technical limitation that make some rendering hard and I’m not as pessimistic, the gist is that Murgilod is right nonetheless on the challenge.

The first thing people don’t understand about cinematic lighting is the heavy logistic behind it! Even for lighting a simple dinner scene, and then you have heavy post production to make it good.

Look at how the light is heavily motivated artistically with all sorts of angle that doesn’t come from the diegetic lamp in the supposed scene. Basically all these set up LIMIT where the camera can be, and that’s like a hard technical limit of reality.

So? Nobody is arguing against that.

@neoshaman

You actually don’t want, because that’s literally not necessary.

There is a lot real lighting rig does to mitigate natural effect of light, all these effects aren’t needed in game where we have absolute control on lighting.

For example if you want soft lighting, in game you can just wrap the lambert and be done, in movie you will need a ballon lamp and choreograph around it because using it has a serious spatial commitment.

Wrap lambert is only fine when you’re dealing with PS2-level graphics and you don’t care about shadows. In ray tracing renderers you can just add emissive lights wherever you want to and make them invisible to the camera. No need to break your BRDF. This tech allows for this.

@neoshaman

Other thing you can do in game, that aren’t technical limitation, people making movie would love to have:

• selecting which object cast shadow/light and which receive shadow/light, and at which intensity.
• add selective texture to shadow/light.
• have arbitrary fall off curve.
• have actually thousand of invisible light in frame, instead of having to build jinga tower and electric nightmare to host a few lights that cannot be in frame (and not having to deal with fire hazard or teh intern tripping on the cable).
• selectively have bounce lighting when needed where you need, and the ability to selectively block it.
• Straight up paint light if possible.
• decouple shadow from objects.
• arbitrary and evolving material reaction.

All of that is done in CGI films.

@neoshaman

So to come back to the horizon light issue, it’s artistical through and through not a limitation, and more importantly this specific technique won’t help, you would need to demonstrate that zillion shadow actually help, which nobody has demonstrated except invoking magic resolution.

The horizon lighting is more of deadline/big organization problem. You have limited time to try new thing and refine them because you have to ship. There is probably way to mitigate it that already exist, like placing lightprobe and using the directional value to modulate the 3 point lighting intensity to make it more plausible, BUT that mean spending time figuring out the in and out of the method. AND the SWTOR talk I shared earlier kind of did that in some way, where in dialogue, it use the real light direction and modify it to keep it in plausible range while having cinematic quality, so that’s not a technical constrain as this game is old AF.
https://www.gdcvault.com/play/1014362/Cinematic-Character-Lighting-in-STAR

ANYWAY this discussion has reached locktown level, There is nothing new to explore or say.

No, the hard shadows in Horizon are a technical limitation through and through. Zillions of shadow casting lights = natural looking area/emissive/indirect shadows.

@Murgilod

Oh my god you’re worse than OCASM.

Those shadows are nothing and we already have plenty of things to replicate what you’re confusing with shadows there: caustics. You aren’t just missing the forest for the trees, but actively ignoring it. Do you need millions of dynamic shadow casting Christmas lights? No, you don’t! In fact, you probably only want a select handful of them to cast shadows and only at a certain distance!

Why?

Because, once again, we have to consider the artistic side of things here. Players will not be looking at every part of the screen all at once and, instead, will be looking where their eye is guided by the design part of games. Textures designed to catch the eye, to concentrate detail, to make the scene look readable so the player knows what they can do and where. You can do all this with a small handful of shadow casting lights, and it does not require special tech that can render millions of them.

Again, you have not presented a practical example, but rather presented an edge case that still isn’t representative of how we deal with light.

This is not the 90’s. PBR is the law of the land and realistic lighting is a must to make the best of it. Game assets and materials are up to the quality of CGI films but rasterized lighting holds them back, massively.

[AcidArrow]

So I just skimmed the thread, but regardless let me add that if you need million lights to make your scene look good you’re doing it wrong.

[UhOhItsMoving]

[blueivy]

And now Unreal has RTXDI for all GPU’s. I hope Unity will look into implementing this into their engine since one of their researchers has already worked on this tech SIX years ago.

Unreal Engine 5.5 Megalights - Tech Demo | Unreal Fest 2024

Combining Analytic Direct Illumination and Stochastic Shadows

[GoGoGadget]

Please, please no.

That is objectively bad tech. It is purely reliant on TAA and according to those who have dipped into the source code, relies on 12 history frames worth of data to get something that’s ‘just’ usable. That’s why in the demo they didn’t move fast at any point, it would turn into a smear-fest. We don’t need to suddenly add noisy shadows into our games because artists don’t want to learn simple shadow/light optimisation.

[blueivy]

It’s called having options, that’s the whole point of HDRP, enabling options for people who want higher graphical features. Lol who say’s please no to someone asking for an option feature that would benefit developers, no matter if it requires TAA or not.

[Murgilod]

Then implement it yourself.

[DragonCoder]

Even if it were to be only useful for slow cam movement, there are games like that and especially for cutscenes that’s typical.

Of course it’s a valid question whether that should be where Unity should focus on first.