Does Ue4 support Area Lights?

melviso · May 2018

In offline renderers, we have area lights like this:

Image: https://us.v-cdn.net/5021068/uploads/editor/c6/g5p9twln8irt.jpg

I have tried looking this up on ue4 documentation but all I can find is directional lights, point, sky, and spot. Is there a way to fake it for dynamic lighting in ue4?

JordanN · May 2018

Area lights are available with the VXGI 2.0 extension for UE4.

To be honest, I thought they were already added in a previous update but I guess not.

https://www.youtube.com/watch?v=g3kLO-4fZRc 

Joopson · May 2018

Sort of. Point lights have an option called "source radius" that can give the light an "area" effect. But, as far as I know, not as a rectangle.

https://docs.unrealengine.com/en-us/Resources/ContentExamples/Lighting/5_1

And, you have to bake it for the shadows to look right.

Obscura · May 2018

Yep. Source radius can be used to make the specular highlights look like how they would look when they are created by an area light. Also, when mesh distance field generation is enabled in the project settings, ray traced distance field soft shadows are used on the lights, and source radius determines the shadow softness - plus the distance from the shadow caster etc, as its expected.

Distance field resolution on the meshes needs to be pumped up quite high to get good looking shadows though.

Obscura · May 2018

^ That is for dynamic lighting though. There is a better quality way for static lighting, through emissive materials on meshes. To do that, make an emissive material with some intensity, apply it on the mesh, and enable "Use emissive for area lighting" - its called something like that - on the mesh properties.

More here:
https://docs.unrealengine.com/en-us/Engine/Rendering/Materials/HowTo/EmissiveGlow

With this, you could have plane lights, or any light shape

melviso · May 2018

Thanks guys for the info, will look into them asap : - )

What about emissive lights with ue4 lpv. Does that work?
Also can I get a light to only cast shadows and not light a scene or objects?

leleuxart · May 2018

Like others have said, yes for spherical and cylindrical, but no for rectangular or any other source. Although, texture-based area lights are coming in 4.20, with some limitations of course.

You can use emissives with LPVs, but the last time I used them it was horribly broken and really sensitive to intensities. LPVs have had minor improvements since then, and they seem to work okay now, but I can't say for sure about the emissive part. It did work though.

melviso · Jun 2018

@leleuxart Thanks.
About DFAO, I did some research about this issue:

Image: https://us.v-cdn.net/5021068/uploads/editor/2f/az8ljsbr1qdt.jpg

Seems this is caused by dfao having issues with large meshes. What is the least smallest size that can work with dfao without this artifacts and splotches using dynamic skylight? The above is visualize distance field ao.

Obscura · Jun 2018

Large meshes shouldn't cause errors unless the distance field resolution is too low.

melviso · Jun 2018

Obscura said:

Large meshes shouldn't cause errors unless the distance field resolution is too low.

I tried increasing the resolution, it's still very unsightly. These are threads I have looked into and non uniform scaling seems to be any issue. I think they mean not using rectangle shaped meshes that are too long in one direction.
https://forums.unrealengine.com/unreal-engine/feedback-for-epic/49632-4-9-horrible-dfao-artifacts
https://forums.unrealengine.com/development-discussion/rendering/101613-combining-a-movable-skylight-and-directional-light-causing-unpleasant-shadow-bleeding
From this vid, they use modular meshes that are roughly squares in shape to avoid artifacts issues. I wonder how the interiors are that clean or did they turn of df shadows for those interior walls?

https://www.youtube.com/watch?v=vef_ZPLhjt8

Obscura · Jun 2018

You could use long thin meshes, but they should be modeled like that, instead of making them long by applying non uniform scale.

melviso · Jun 2018

Testing different scenes using LPV and dfao. Can dfgi and lpv be used together? How does DFGI compare to LPV?

Image: https://us.v-cdn.net/5021068/uploads/editor/ic/8bvzqhby54x5.png

Original scene above by Koola. No baked reflections with screen actor capture yet.

Image: https://us.v-cdn.net/5021068/uploads/editor/8c/o65f339rexl1.png

Image: https://us.v-cdn.net/5021068/uploads/editor/5a/payy4vcssq7l.png

Obscura · Jun 2018

They can probably be used together, but I haven't tried. I would say dfgi should give you somewhat better quality. Personally I find lpv the lowest quality out of all of these bad "gi" solutions.

Have you seen this?
http://timhobsonue4.snappages.com/distance-field-global-illumination

Whats the problem with lightmass by the way? Your scene isn't moving so you don't need a dynamic solution, and lightmass gives you waaay better quality than these anyways.

melviso · Jun 2018

This are simple scenes. Lightmass can take up to 24 hrs to maybe more for very complex scenes. The worst are the light leaks, it's been frustrating especially dealing with it when the focus should be creating art. Some games are switching to dynamic because of this issue. Even this guy uses dynamic.
https://www.youtube.com/channel/UCgmX4icpN3HnOOwYtmyYz2w
EDIT: Seems dfgi has been removed from ue4 since
https://forums.unrealengine.com/unreal-engine/feedback-for-epic/1469233-please-bring-back-dfgi-in-4-19-4-20
I entered the code in the consolesvariables.ini but it doesn't show up when ue4 editor is opened. Distance field Gi is missing if u check the visualise tab.
So DFGI is no longer in ue4.

Obscura · Jun 2018

Professional game developers will prefer performance and quality over workflow speed so I'm not sure what kind of game developers switched to dynamic lighting for such reason

Leaks are annoying for sure, but they can definitely be solved.

If the baking takes long, you can distribute render with lightmass. You can bake using multiple computers. Also, for previewing, you can use lower settings, and pump them up when you are done tweaking and you want your final lighting.

melviso · Jun 2018

Obscura said:

Professional game developers will prefer performance and quality over workflow speed so I'm not sure what kind of game developers switched to dynamic lighting for such reason

These devs did because of lightmap issues

https://www.youtube.com/watch?v=c2YL9L-OZg4

Leaks are annoying for sure, but they can definitely be solved.

If the baking takes long, you can distribute render with lightmass. You can bake using multiple computers. Also, for previewing, you can use lower settings, and pump them up when you are done tweaking and you want your final lighting.

I know

Just that these light leaks can really get frustrating especially for certain interior types.

Obscura · Jun 2018

Personally I think that was a bad decision from them. It doesn't look good, but thats just my opinion. Its flat, game-ish, kinda previous gen looking. Its also more expensive for no real reason. Not to mention the issue with reflections. But well. Everybody can have their opinion and preferences.

JordanN · Jun 2018

IMO, it's high time we start getting some next gen announcements. It's been 5 years since PS4/XB1 came out, which is usually the same time developers start asking for new tech.

Maybe not this year, but hopefully in the next, we'll see new hardware to help progress dynamic lighting. Especially with everything moving to PC, it's a matter of just scaling these solutions down instead of worrying about crazy architecture.

radiancef0rge · Jun 2018

realtime gi does not look better and it generally costs over 2ms to just get one bounce. devs will prioritize 16ms scenes over dynamic gi.

Joopson · Jun 2018

JordanN said:

IMO, it's high time we start getting some next gen announcements.

I'm sure I'm not alone when I say: it's way too soon for another gen of consoles. The 360 lasted 8 years, but I feel like devs got a really solid grip on what it could do, and really pushed it to the limit, by the time the next gen came along. To some extent, I still feel like this gen hasn't reached its maturity yet. And until it does, I don't think throwing tech on top will help games look much better.

As for Sunken City's dynamic lighting. I think it looks good. But it definitely looks flat-ish and game-like. Like some early UE4 games.

JordanN · Jun 2018

Joopson said:
I'm sure I'm not alone when I say: it's way too soon for another gen of consoles. The 360 lasted 8 years, but I feel like devs got a really solid grip on what it could do, and really pushed it to the limit, by the time the next gen came along. To some extent, I still feel like this gen hasn't reached its maturity yet. And until it does, I don't think throwing tech on top will help games look much better.

As for Sunken City's dynamic lighting. I think it looks good. But it definitely looks flat-ish and game-like. Like some early UE4 games.

Keep in mind, PS3/360 lasted as long as they did because they used crazy architecture. 360 had unified shaders that wasn't possible on PC until the Radeon 2900 came out in 2007. And PS3 had the Cell CPU which was notoriously difficult to work with that it scared a lot of Japanese Studios into releasing their games late.

But the PS4/XB1 didn't launch with such groundbreaking technology. Both consoles are using off the shelf hardware with specs equal to low to mid end PC's when they first came out.

With technology getting cheaper over the years but the gap between console & PC has gotten far bigger, a new hardware announcement would at least inspire developers to take greater risks in outdoing the competition now that the baseline has been raised.

melviso · Jun 2018

I found this. Ue4 might be having some serious competition:

https://www.youtube.com/watch?v=tEtWzaq4D4I
But the engine isn't free though.

Can some one pls tell me how to launch building lighting through the command line? The command line is it in the output log or it's done without opening ue4? Sorry noob question.

musashidan · Jun 2018

Unigine is voxel-based GI. And you might be very happy to know that it doesn't require lightmap UVs at all.

Pity about that horrible 'washing powder advert' voiceover.....

The engine is more aimed at Arch-vis/simulations/engineering/etc, so I don't think UE has anything to worry about from the games industry. Although for your work it might be perfect.

It is expensive, though, especially in comparison to the zero cost of UE.

melviso · Jun 2018

I know. The price is very high. At some point they might go ue4 route. Some game companies are already using it I think.
Would u know anything about starting building lighting using a command line? Is it done using the output log?

Does Ue4 support Area Lights?

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