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My Walls have light entering the edges

Hi im having a problem with lighting. My project is an architectural visualisation and i have separated walls into different groups in order to get maximum quality out of the lightmaps.

I have an issue with the lighting as the light seems to go through my walls and bleed from the edges. My build is on production and my walls lightmap sizes are 512x512 and the floor is 1024x1024. I have let unreal engine 4.5 generate the lightmaps for me.

I have used a spotlight from the exterior to represent the sun and a plane for it to reflect on, just like the market place content "xoio Berlin Flat". Is the problem that my floor and wall are not 100% in the right place and not connecting? or my UV mapping is bad?

I have provided images of what i have explained above and also the problem, id like to thank you in advance for taking the time to reply.

alt text Image showing the light bleeds in the dark areas of the room.

alt text My lighting technique using a plane and spotlight shining on it to reflect back into the building.

alt text Showing my asset settings for the wall

alt text Lightmaps settings for the floor

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asked Dec 12 '14 at 05:04 AM in Rendering

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StefanTheArchitect
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avatar image Huppys Dec 12 '14 at 08:38 AM

I'm not quite sure if I get this right, but it looks like your mesh is not closed (saw light_bleed_lighting2.png). Did you try a mesh without holes?

avatar image StefanTheArchitect Dec 12 '14 at 08:44 AM

thanks for responding. Those are just where the other wall that is isolated belongs i dont think that is the problem. I changed my objects to movable and i changed my light to movable and it got rid of the bleeding. Any idea why? in the images above the light and the objects are both static. I have no idea why the static lighting and objects cause bleeding but the movement types dont.

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Hi Stefan,

Can you try building the lighting in Production mode if you've not already done so? Preview and any mode lower than Production can generate the light bleed you're seeing, in most cases. If that doesn't solve the issue then it may be that you need to revisit your lightmaps and set the hard edges to snap on the grid in the UV space for your hard edges. The grid will need to be set up to the lightmap resolution you're targeting.

You can find more information about lightmaps here in this forum thread. There is a lot of information being discussed that can be helpful. https://forums.unrealengine.com/showthread.php?46269-Modular-Asset-Lighting-Problem

Thank you!

Tim

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answered Dec 12 '14 at 02:21 PM

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Tim Hobson ♦♦ STAFF
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avatar image StefanTheArchitect Dec 13 '14 at 04:53 AM

thanks for replying Tom. Ill try that out and see if it gets rid of all the light shining into the bathroom from the outside

avatar image StefanTheArchitect Dec 13 '14 at 01:08 PM

Hi Tom

i tried what you shared and i still have a problem. Ive been having this problem for months and i can never seem to figure it out. I made two buildings one with manually adjusted UV's and one automatically generated by unreal engine's 4.5 new lightmap generator. Can you please take a look at what i am doing wrong i cant figure out why i my interior always seems to have light bleeding from the edges of my walls. I have provided a link

Unreal Project - https://www.dropbox.com/s/wgijj62i4z4n65n/Arch_Building.zip?dl=0

Thanks.

avatar image Tim Hobson ♦♦ STAFF Dec 15 '14 at 06:23 PM

Hi Stefan,

I'm going to go ahead and show the image of my results and then explain a little how you should be able to resolve this. It will require a little bit of rework and rethinking on some things I'll do my best to explain. if something seems a little odd or you're unsure please ask and I'll explain more clearly or with better examples. :)

alt text

In the main room there is a lot of light coming through that is carrying over and bleeding into the lightmaps for the other rooms.

1 & 2: With your Static meshes I would not leave any open faces to help block the light. Having the holes in the mesh can allow some light leakage. I don't think this is the main cause for a lot of this but having a couple of extra polygons to help block light if there is any leaking will not hurt. This may help by using a method similar to what I'll describe in steps 3 and 4.

3 & 4: With the single floor piece being used across the entirety of the building it can cause light leaking. When the lighting is baked it's allowing the light to cover a lot of the mesh and thus the bleeding. To prevent this using multiple floor pieces, which is demonstrated in 4 will all only light to be baked on the side that that mesh is part of.

Increasing LM resolution will not always get rid of this kind of light bleed. Using multiple closed meshes to control the lighting is the best method to get the results you need. There will inevitably be seams from the meshes next to each other but this can be reduced by using the World settings and adjusting the Indirect Lighting Quality (2 or higher) and Indirect Lighting Smoothness (0.6 works well) to reduce this effect.

archbuilding.png (485.1 kB)
avatar image Tim Hobson ♦♦ STAFF Dec 15 '14 at 06:23 PM

Another thing that may help, but I don't necessarily recommend it without trying the other methods would be to go into world settings and adjust the static lighting level scale to a lower value. There may be some artifacts here as well but this can probably be reduces with the lighting quality and smoothness settings. Try a value that's lower like .75 or .5. This will increase light build times though.

Tim

avatar image StefanTheArchitect Dec 16 '14 at 05:27 AM

Thank you so much for replying Tim.

Ive started a new project and it has fixed the light bleeding problem with the help you provided. I also re did the grid snapping for the UV lightmap channel using a 512x 512 lightmap resolution.

i calculated 1/512 = 0.001953125 and have snapped all the vertices to the grid in 3DS MAX. My only problem now is i get some weird shadows on parts of my walls and slabs. The look like splotches on the wall. Any idea what is causing this to happen or how i could fix it?

Thanks so much.

alt text

shadow.jpg (113.5 kB)
avatar image Tim Hobson ♦♦ STAFF Dec 16 '14 at 04:47 PM

No problem at all! :)

I may have to open the test project back up and toy around with some of the things, but if you're still using the floor template mesh for the floor this may be the issue you're seeing there with the large shadowed band. Some of the splotches are the results of using the Indirect Lighting Smoothness. Trying bumping it up a little if you changed that down to 0.6. The lower you go the more artifacts (splotches) you are likely to see.

The alternative though with all this would be to use a single mesh to prevent any light bleeding. Although you would need to use a slightly higher LM resolution to get good cast shadows I don't think you would need anything exponentially high. 512 to me seems high at the moment. It might be worth investigating exporting you mesh as a single FBX and using the auto-generated LMs (as a test) to see how well the LMs come out.

Let me know if any of that helps.

Tim

avatar image lanfranconi Apr 02 '19 at 05:34 PM

This is nearly the only useful post about light bleeding, which is a big issue for new and intermediate archviz unreal users. it took me a while to find this post, forum and google searches lead to all kinds of outdated, speculative and ill-informed guesses. this thread should be prioritised in the search/forums. This issue has plagued me for weeks now, glad I found this.

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