Flatten Mapping

You’re going about it the completely wrong way. There’s a lot of things that need to be done. First, you need to break up the mesh into multiple objects, you shouldn’t have it all as a single mesh. Especially if something is used more than once you only need one of them. Also, for lightmapping you would need to make sure that the meshes are split enough so that you have enough lightmap detail, so if you can’t get enough detail with a high resolution lightmap then you need to split it up further. It also looks like your scale is too small. 1 unit in UE4 equals 1cm.

Yup what Darth wrote, above.

I just want to add that for such buildings, split it all into sections/modules.
Then make blueprint that creates buildings out of those meshes in construction script.
This will save you time later.

Guys, i see what you saying. I started dividing splitting my building now. Is there a way to increase UV base size guys?(so UVs will be more detailed)

My second question is what is “Overridden Lighting” ? When we check this option on UR4 , some of the objects suddenly looks all right.

When you check that option it’s reverting to dynamic lighting until you build lighting again.

The override allows you to set the lightmap resolution you would like if you need it to be an instance specific thing. Otherwise you can set it via the static mesh editor > Lightmap resolution. The default resolution is set to 32 which is quite low if you have a large object.

Breaking the mesh into pieces as suggested and using a LM resolution of 512, 1024 could possibly help. I tend not to go higher than these unless it’s absolutely needed. Which is very rarely and typically only when I’m testing something.

Having a good UV layout will help more than anything else at getting the most out of your Lightmap UV and having your asset broken up so that the pieces can occupy more of that UV space is key to getting decent resolutions with your mesh.

Thanks Tim. I get what you saying. Will using Blender make unwrapping any easier?

I have a new problem. When i import a house with all different component(railings, windows and walls) . UV’s of all the objects will be stored in only 1 UV base. So all they are overlapping. You can see railing’s UV’s over Windows’ and walls’ UV’s . That is probably one of the issues troubling me.

Personally, I’ve not used Blender so I can’t attest to their Unwrapping ability and ease of use. I use 3Ds Max with all my modeling and unwrapping. I’ve tried some of the add-ons to make Unwrapping easier like Unwrella and the standalone program for Headus UVLayout. They all have their goods and bads I’m sure, I just didn’t need them beyond the trial to continue my work.

For the overlapping UVs. If you’re using multi-sub object textures so that you can have all these pieces occupy UV 1 and use different materials that should be fine. I use this method a lot. As long as each material is assigned to it’s own object the material ids will be OK and now show metal railing on the windows where they overlap. In this type of case the UVs overlapping is not a major concern.

In my opinion it’s nearly the same as in other 3d programs (3ds max, maya, C4D) -> you can either use the existing features or download a plugin :slight_smile:

Tim, it’s so weird. When i import only 1 object, UV’s are fine and when i build it , it look OK. But when i import a couple objects at the same time what i told before happens. And non of them are assigned multi-sub object.

Fighter, thanks :slight_smile: . I thought so.

When you’re importing are these all individual objects in a single FBX that have the “combine meshes” option disabled on the import window or are these separate FBXs that all have mult-sub-object materials?

Also, just to confirm, you’re on Version 4.6.1?

Timmm, dang it! I didn’t know such an option existed. Wow! Thanks. Let me keep working on the project for a while. I am sure i will come across with more and more problems soon. Thanks :slight_smile: .

haha no problem. :slight_smile:

I check the forums often, so if you have any issues feel free to post. If I’ve not checked in a couple of days feel free to shoot me a private message if none of our awesome community members have offered any help as well.


I’ve just added a new Wiki page to my forum posts here: [TUTORIALS] Photons Be Free: Mini-tutorials and other curiosities - Community Content, Tools and Tutorials - Unreal Engine Forums

This is listing all the troubleshooting and lighting tips that Eric and I are working through to get listed.

The page is already active on the Wiki with some issues. One that is on our list to get to is unwrapping large objects with a comparison of Flatmapping vs breaking into smaller pieces. This is really a common issue that comes up and it could be helpful for others like yourself that run into theses issues and don’t know exactly what to do. Feel free to add to the post if you’d like to see anything added that’s not listed or have any suggestions for anything else. :slight_smile:

Tim, thanks so much. Great to know having someone like you ready to help any time. I loved your little tutorials. Thank you.

Guys, isn’t there a plugin on unreal engine that works like “UVW Map” on 3ds Max? Do i have to do unwrapping for everyyyyy single object on Max? Even for the objects that doesn’t have any texture on it? For the ones that only have a white color material on it? There gotta be something to handle this operation easier way.

Another question is , even for the objects which wasn’t unwrapped in Max, Unreal generates an additional UV map which is very similar to flattened maps of Max. What is this?

UVs cannot be edited via UE4. There is no plugin that has been created yet by anyone. UE4 can generate lightmaps though for your second UV channel. This will only repack the UV used for the texture though. So, it will not break any seams or flatten any things out that is using a projection UV method, which can lead to overlapping UV errors. It’s best to do the UVs in Max or whatever program that may be used to handle UV Editing.

The objects that need a lightmap really need need to be unwrapped. Flatmapping can work OK for smaller objects or ones that you may not need to worry about as much, but for your “Hero” objects that need the attention really need to be unwrapped in ways that get the best results.

This will walk you through the process:

Essentially this is a RE-PACKING of your texture UV. It will take the UV shells that have been placed and repack them to have proper padding/spacing between other UV shells based on the minimum LM resolution you select. To reiterate again form earlier, if you have a lot of UV shells this will mean that the smaller the UV shell has to be in this space will be the less amount of resolution applied to that shell. A resolution of 32 or 64 would be really low for a large object broken up in pieces. Each one of those pieces would only be getting a minuscule portion of the LM texture space.

Tim, thanks so much for all the detailed explanations and links. Here some new questions:

1- Is that “Generate Lighmap UVs” option necessary** only** if i didn’t unwrap a lightmap in Max? Should i enable this option when i already unwrapped my own second channel UV in Max?
2- When you use the modifier “UVW Map” in Max and select “Box” mode, it works for most of the objects. But why doesn’t it work in Unreal. Or does it ?

  1. Yes if you want to have a lightmap with your static lighting. The answer is also, No. If you have a well laid out texture UV with no overlapping faces and enough padding you can use the Texture UV as well. This option was added in 4.5 to make it easier for those who didn’t know about 2nd UVs and didn’t understand what Lightmaps were when just starting out with the editor. The generated UVs has been there in some form since UE3/UDK. It was just refined a bit.

  2. There are some caveats to using UVW Map. It can be used in Max to get your UV the way you like. This method will still produce overlapping UVs if you just apply a UV Map modifier. When you import just make sure the checkbox for “Generate Lightmap UVs” is set. This will take those projected faces that have been split apart and repack them. I tested this using a Cylinder, Box, and Sphere with good results. If you do not import with the option to generate lightmap UVs the mesh will have the “Invalid Lightmapping settings” material on the mesh.

Tim, thanks , thanks , thanks. Completely understood. I won’t be disturbing you for a while now :slight_smile: .

No worries. :slight_smile:

I enjoy helping and it helps me keep up with it all and learn new techniques as well.

Got this fortune cookie message today and it is absolutely true.


Guys, how to change UV resolution on Max?

I have same problem. Overlapping wake up when use wrong export options. Setup your fbx exporter like show in doc.