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Black Corners and Light Leak after fixing black corners


I'm new to UE but I'm not a new to 3D and app development.

Lately I did a small ArchViz project and when everything was done I said lets make Production build (UE 4.18.3).

And I got this error in many places:

alt text

So Light map resolution is there and it have space do do those places smooth. And also there is a 45 deg angle between the walls. But why do I need to have everything on 90 deg angles ?? There must be a way for this.

When I started to going through all posts and what everybody got to say about this I found a solution. My problem was lightning smooth. I made it sharper so that’s why I got that pixelated edge. So I set it up to 1. And my problem disappeared.

alt text

But the I went out of that room I saw a massive light leak in the corridor outside of that room with error on the sealing. And again I started to messing around with the settings and mesh configuration and its just staying there.

alt text

I also started to mess around with lightmass.ini file which didn’t sort out my problem but extended render times to infinity.

I do have all my UVs pixel perfect with gaps. I do not have any lightning errors based on this issue.

My mesh is solid and got 10cm thickness.

My set up is just 1 directional light standard settings.

My questions are:

1) My initial problem with black edges was a surprise for my. But I was doing a texture backing in the past and every time there was a setting of color bleed (overflow) out side of UV island to avoid any problems with black corners (in pixels). Why in UE this is not available ?? That will sort out everybody’s problem. Cause islands in UVs must be separated with a margin to work properly. Why not use this margin for color overflow.

2) How to remove those light leaks. Can this be a problem that my outer walls and sealing and floor of that level is one mesh and the inner walls are another mesh??

3) Should the walls touch or intersect sealing?? Cause it did not work for me any of those scenarios.

4) Should you remove top walls polygons that are touching sealing and floor?

5) Why when so many people have a problem with light leaks UE team did not fix this yet. Light in a baking process cant go thru static mesh. That's it. There is no more to that. And a lot of people got problem with that and they start to messing with lightmass.ini file with is totally not documented.

6) Why the lightmass.ini settings are not documented?? Or are they?? And why there is no advanced lightning settings tab so I can set them up for the specific project / level?? This is to much to ask for ??

7) When I create a walls of a floor lets say ground floor and level 1 floor on the edge between them there is visible indirect lightning difference. I understand that this is made cause of the modular approach. All my kitchen shelf’s got problem like this as well. Solution to this is to put 0.1 sample size. But that creates artifacts of the skylight HDRI and you can prevent this with Hemisfere samples in lightning ini. But Jesus Christ its the same problem. Why did you not fix this. Buy having a setting or grouping. “This group of modular mesh must be treated as one object for static lightning build”. Done problem solved. I just told you which meshes should be aware of each other. Cause forum says this is the problem for those calculations. And this is a game engine everybody wants this modular structure of levels to work perfectly. And in my case it turned out that I must join in a bigger mesh smaller reusable elements as I go.

8) Why your automatic generating UVs process is not pixel perfect?? You got the setting for minimal mesh and what the mesh should be in the time of baking. Can you not generate the UVs before the build process to be for the size and pixel perfect so the will be no light errors??

9) I think a lot of people will also be interested in this cause there was a post about that functionality: “Save all and turn of pc after build is done”. Cause I left my pc running for the night couple of times and its just buzzing next door for no reason.

10) Dynamic lightning with LPV is terrible. In my scenario I was having black sealing or just one big squire on sealing color gradient simulating window light bounced from floor. A lot of those setting ware a nightmare to set up and find what they do. And in the end result was terrible. And buying a third party plug-in for lightning is really something strange. VXGI – when I saw the set up process I gave up eminently. I do not have a day of just to set this up.

Don’t get me wrong. The engine is superb in my opinion. But its version 4.19 (that BTW is still doing all of those problems) and I as new user have those problems still. There are even videos telling do not use UE4 if you are not ready to do this crazy s...t. And its true. You must be prepared for a nonsense work just because there is no simple settings for that.

I can tell wright now which ArchViz was done with UE4 and which was not. Cause most of them will have black lines in the corner and this is a giveaway out of the box for me. And this is not a good reference. Or you have good light and short times of render but black lines in the corner. Or you wait forever and will have massive light leaks because your mesh/uvs/setting was wrong.

Sorry, try do better next time you press that build button.

Sorry UE Team but you need to fix this. This process must be better.

Or give me a setting “Super production – you can leave your pc frozen for 24H but its going to be legendary (100% no light issues)”

Product Version: UE 4.18
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asked Feb 28 '18 at 11:26 AM in Rendering

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avatar image Gnorkie Jun 04 '18 at 01:08 PM

Following this, I'm having the same problem (as many others).

AO is OFF, in project settings, lightmass world settings and in post process volume.

All lightmaps UV have been created is Max and setted properly, and lightmass density is green or higher everywhere.

avatar image Makigirl Jun 05 '18 at 02:36 PM


I think you should start your own post with your own pictures and settings... /as you can see he wasn't really cooperative just frustrated.../

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3 answers: sort voted first


Hugh! :) So IMO:

2) Dark edges are kind of a bug but I'd say it's "always" solvable. And most of the time it's lightmap uv related or "over tweaked" light/post process settings... If you're after archviz quality I would keep all your walls separate and sometimes even break them up to smaller/modular pieces to get better resolution.

3) They shouldn't touch nor intersect: they should be snapped at corners!

4) That's another solution: you can uv map just those non touching/visible parts for lightmap the same way as they appear. But I'd never "open" mesh up but leave it solid.

5) There is no need to mess with the baselighmass.ini! Before portals yes but since then not really (extreme cases). Yes many people have problems with it any many don't... Don't forget that Unreal wasn't made to render archviz scenes but making games... We are forcing the engine hard to get those incredible renders! And Unreal team gives us a lot of support and development towards that direction!

6) You can set everything in the editor for beautiful archviz renders you don't have to touch baselightmass.ini (although there is a really nice summarized documentation somewhere on the forum!!

7) Before getting angry or frustrated you should read more about the subject... HDRI creates artifacts: why to be surprised if your scene is related on it and you keep it on 1 bounce?

Good luck! :)

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answered Mar 01 '18 at 01:00 AM

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avatar image none_none_2000 Mar 01 '18 at 01:06 PM


2) That is a bug. My Uvs are 4096 minimum 2048. and as the image shows overlay there are pixels available to smooth that black edge but are not used for that. I do not have post process on this one at all yet. And setting are default or tweaked just like the screen shows. Not to much. I will try to split in to smaller meshes but what to do with the sealing?? its big flat surface.

3) I got this they are snapped.

4) My mesh is not opened but to much mesh creates artifacts on outer walls based on modular module. And setting smaller Static Lightning Level Scale (to avoid different lightning on modular flat surfaces) creates more artifacts and more dark corners.

5) for those renders I do not mess up ini file. But I did some tests and the didn't work. I also think this should be working on default settings Just by changing render quality to production should solve the quality totally.

6) I read all the documentation and forums. I try so many solutions now (even now one render is finished just 2 minutes a go and still black corners). I really read a lot about that topic.

7) I do now that they do that's why I do not have it. I just have 1 directional light. But I do know how to sort out HDRI quality issues with .ini file and this works. But leak I got with just 1 directional light. HDRI is not creating the leak at all even with more bounces then 1. I tested this already.

Anything else ?? Somebody from UE Team is reading this ??

Another person says its a bug. Please fix it.

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You say different settings every time... :S It seems to me you're just angry and don't really want solutions... Believe me you get these results becuse your setup is wrong!! ...and I don't think that with this behaviour you'll achieve anything here... if you're unsatisfied with this free software and it's beyond your capabilities to use it why don't you change to another one? Oh yeah you're right and know everything just angry I forgot! :S

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answered Mar 01 '18 at 02:00 PM

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avatar image none_none_2000 Mar 01 '18 at 03:45 PM

OK not helping.

I got my experience with 3d software and I do think is great (I mentioned this in my post). I do get its porous games and I know it can be stretched to photo real.

I try different solutions every day for last 2 months and I need new solutions and not telling me am I angry or not.

I restarted my scene like 5 times now starting from the scratch and I got the same results.

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I would really like to help to solve your problem!! Could you upload your scene please somewhere that I/we could take a look? ...I'll have time tomorrow evening...

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answered Mar 01 '18 at 04:05 PM

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