What caues errors for lightmap uv overlapping with BSPs when no BSPs are overlapping?

I was fitting the second floor to the shape of the room. After rebuiling lighting I got this error:


I turned on error checking and nothing was wrong. Is this a bug? I updated the most recent for 4.4.2.

If I delete the selected grouping in the picture and rebuild then for some reason I don’t get the error anymore. I don’t know what is going on. Can someone help?

Hi ddtapia,

Is this object in your scene outliner as well? I’ve had objects in the past that the mesh has been deleted but the reference to that mesh is still present providing a similar issue. To look further can you answer the following questions?

When you click on the “None” does it take you to the asset that is causing the offending issue? If so, can you replace it with a new BSP that does not cause the issue?

If you’re able to recreate this in a blank or template project can you provide the steps to reproduce the issue? If so, this will allow me to get a repro on my end to test.

Thank you!


HI Tim,

Thank you for asking =)

All the cylinder objects appear in the Scene Outliner.

When I click on nothing happens. I know if I delete the group it will build fine. but when I put another group in the area it gives me the error.

Umm well see this is a small part of much bigger level, I am not sure you want me to recreate the whole level because that would be a very long time and list of instructions.

this error came about when I was fitting the second level floor to the room. In the picture, when I extruded the top left area is when I got the area with that group but when I deleted the group right after that, the error did not show on the next light build.

I’ve been trying to get a repro for this but am having no luck. BSP can be finicky when you are using a lot of them. If you have a lot of them in your level this can cause known issues to occur like faces going invisible and crashes that occur sometimes when editing vertices on the BSP.

Would you be willing to share the entire level via a private message on the forums? I would only need to .umap file for your level since this is BSP related and no other assets causing the issue.

Thank you!


Hey Tim,

Yes or I can email it to you, whichever is easiest.

If you want you can send attach a link in a private message on the forums.



Alrighty, Got this one figured out for you.

It’s more of a good news/bad news time because it will probably take a little bit for you to get this one sorted.

I got rid of the “None” error by removing all the static meshes. This indicates that it’s not the BSP that is the issue. You have references to static meshes in your scene outliner that are no longer in your content browser.

For instance, If you placed a mesh in your viewport and then deleted the mesh from your project through the Content Browser it will still leave a reference to the object in your viewport. It will no longer have a mesh and will only have a pivot point but it will still be there. This is where the issue is coming from.

The bad news is that since you sent me only the project map and your project potentially still has the normal meshes along with the map you’ll have to sift through the scene outliner and see which reference is still left behind.

I hope this helps and let me know if you’re still having issues.


Oh ok sweet thanks! So this just means all I have to do is go through each item listed in the scene outline and see if it is actually in my viewport and if not then delete it?

That should be it. It resolved it on my end. Give it a shot and let me know how it goes. :slight_smile:

Hey Tim, so I went through the scene outliner and didn’t find any static meshes that weren’t referenced properly as you mentioned represented as pivot points. I found a few subtractive BSPs that weren’t necessary but the problem persists.

Hey ,

It’s going to be one of the static meshes there that is causing the issue somehow. Since I was able to remove only the static meshes from the scene to get things to work right. It may be a process but If you make a copy of the map and then just go through and delete one mesh each time you build lighting (If you put it on preview it should build fairly fast. Only 20 seconds or so on my machine) and go through the 50 or so there were until you find the right one.

That’s the best solution I have for you with this case scenario unfortunately.

Let me know how this turns out and if you’re still seeing the error.



Hi Tim,

So I tried deleting all the static meshes and point lights i had but the error persisted. So I deleted 5 of the Cylinder BSPs in the stasis area and the error stopped. Here is a picture. I don’t know why that is haha. But I would like to be able to keep those BSPs there if possible.

Hi ,

I’ve just gone back through and tried this again and I’m still not seeing the same results. I’ll send you the map I’m using in a few so you can take a look and compare. Not sure why we’re seeing different results here.

Here is a screen shot as well showing no errors on my end after removing only the Static Meshes.

Okay, So I’ve been testing with the latest map version you’ve sent me and I can get the error this time but it’s not related to specifically the cylinder brush. I tried narrowing down which one it was that was causing the issue but was unable to. For instance, I deleted all the Box Brushes and the error disappeared.

This may be a little error that is happening due the amount of BSPs that are in the level. Converting over to Static meshes and setting up proper lightmap channels would resolve the issue.

If you’re plan is to convert the BSPs to static meshes this shouldn’t be an issue in the long run. I’m still going to look and see if I can reproduce this on my end without having to use your level.


oh ok yea that sounds like the best explanation. Thanks for your help so much! I know you spent more time on in than you had to. Yea I will convert BSPs to static meshes at some point. Ok thank you again for the hard work and perseverance! It really shows how much Epic cares about their users!