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BSP Disappear after "Build" for Level

I am having an interesting bug when "Build" my level. I am using BSP for the roof, floor, and walls. I try to use Static Mesh when possible. When I "Build" the level, all of my BSP portions in my level disappear. Only the static mesh items remain. I checked visibility and things pertaining to transparency and everything is normal. This only started when I began expanding on my small level to create a bigger one, obviously using more BSP for the walls, floors, and roofs. I am using 4.7.6 of UE4. Not sure if this matters, but I also noticed this problem after I the Epic Launcher updated. That shouldn't have any affect, but just thought I would add it in this post. Thanks and I appreciate the help.

Product Version: UE 4.7
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asked May 27 '15 at 06:07 AM in Rendering

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avatar image AndrewHurley May 27 '15 at 03:43 PM

Hey MS2013,

Have you attempted to use the "Build All" option as well to see if you get the same result?

I just tried testing this issue and was unable to reproduce what you are reporting. You mentioned occurred after updating the Launcher which is an interesting connection. You could go into your 'Vault Cache' folder within the Epic Launcher directory of your windows explorer and see if any back ups were created of previous versions. This could be causing some type of discrepancy between your versions, although as you mentioned, shouldn't have an effect on your project building.

Can you reproduce this issue in a blank project or does this only occur in your current one?

Thank you,

Andrew Hurley

avatar image MS2013 May 27 '15 at 04:15 PM

Hey Andrew thanks for the reply. I tested the "Build All" function and the build hangs with the lighting build at a constant 0%. If I build the lighting separately, the lighting builds fine. If I build all or build geometry, the BSP disappears. I haven't been able to replicate the issue on any other levels. My other levels build/compile perfectly fine. It is very strange as this only began to occur with the expansion of my level. I checked the Vault Cache as you mentioned and it is empty, probably since I didn't download anything from the marketplace yet. I am not seeing any previous backups being made. Should I be seeing this?

Thanks again for the reply. I am looking forward to hearing some more info.

avatar image MS2013 May 27 '15 at 04:30 PM

Hey Andrew. So I am working on a 1st person template level. I did a build all on the template and the build got to 18% and then hanged. Just thought I would update.


avatar image MS2013 May 27 '15 at 10:26 PM

UPDATE: I have attached some screenshots of my viewport so you can better understand whats going on. NOTE: Build All does not work, so I have to built everything independently.

First image (map after build geometry): This is a shot of what the level looks like after i did a build geometry. As you can see, everything is invisible, but still technically there. you can even see the edge of two box brushes. everything static mesh or game object is still viewable. I have highlighted the wall that use to be there as an example of a BSP that is invisible, but still exists in the world outliner.

Second image (map after dragging a copy of a bsp): I dragged a copy of the same highlighted wall BSP I talked about in the previous paragraph above it. As you can see, everything is back in the level. all the BSP and other missing items are back.

Would be great to get your thoughts on this.

[1]: /storage/temp/44355-map+after+dragging+a+copy+of+a+bsp.jpg

[2]: /storage/temp/44354-map+after+build+geometry.jpg

avatar image AndrewHurley May 28 '15 at 09:14 PM

Hey MS2013,

Thank you for the detailed updates on your troubleshooting progress. This issue does seem to be quite project specific and quite unique. My suggestion would be to convert your BSP walls into static meshes. My guess to what is causing your BSP's to disappear are the several light actors you have within your geometry.

Are they set as Static or Movable lights?

If you still cannot find a way to resolve the issue let me know and we can try to get your project transferred to me so I can test it on my end.


Andrew Hurley

avatar image AndrewHurley Jun 01 '15 at 09:17 PM

Hey MS2013,

Wanted to check-in to see how the issue was on your end?

avatar image MS2013 Jun 02 '15 at 06:22 PM

Hey Andrew. Sorry for the late reply. I have been trying different things so here are the tests/results: Converted all BSP to Static Mesh, however Build All does not work and the lighting UV settings are not giving me the same results as the lighting using BSP. Got rid of all lights in the level, however the same problems occurred. Re-installed the engine, but same problem occurred. While the issue is peculiar and I haven't been able to correct it yet, I can still progress in building the level and simply compiling things separately. Do you have any other suggestions though?

Thanks for the continuing help

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2 answers: sort voted first

Hey MS2013,

So after taking a look at your project, there is really no way of getting around the fact that you need to reduce the light usage as well as converting your BSP's to static mesh actors. The approach I am going to suggest will get you the same results, if done correctly, and reduce the overhead you are generating from using so many movable lights within your structures.

Essentially what you want to do is create a Static Mesh within an external modeling program and set it up as a multi-sub object. In other words, have your lights and wall modeled as one mesh, apply a material to the section of the wall that will represent the lights, and apply a separate material for the wall itself. This way when you import the mesh into the editor, you will be able to assign separate materials and increase the 'Emissive' intensity of the light material to simulate lights without having to use a light actor. This will save your project from a huge overhead, and allow you to create a parameter to set the intensity of all your lights with a single value change.

Light Wall Multi-Material Static Mesh

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Here is just an example of how it can look. Notice the two material slots applied to different parts of the Static Mesh. Each of the light parts are emissive so they illuminate the surrounding area.

Emissive Light Material

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Here is how you go about setting up your light material.

Light Material Instance

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After creating the parameters within your light material, you can right click the material and create an instance. Apply this instance to the light material slot and you can now change the light color and intensity.

Light Wall in Scene

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Here is a rough idea of what it will look like in game with the light intensity (emissive) set to 25. This should get you on your way to creating the level you are going for, without adding too many lights and causing your project to perform poorly. This will also clear any need for BSP's which will resolve your issue at the same time. Let me know if you have any other questions or need additional advice.


Andrew Hurley

walllightsm.png (497.5 kB)
lightmaterial.png (96.9 kB)
lightinstance.png (284.7 kB)
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answered Jun 17 '15 at 04:05 PM

avatar image MS2013 Jun 22 '15 at 06:57 PM

Hey Andrew,

Thanks for all the info and help. Could you perhaps point me to a good tutorial on using an external modeling software, like blender to create static meshes? Also, how do I combine the lights and wall into one static mesh?

Thanks for all the continuing help.

Also, in your wall creation, did you do this in an external editor and then modify it in UE4?

avatar image AndrewHurley Jun 22 '15 at 08:44 PM

Hey MS2013,

Head to our Documentation for advice on how set up a multi-material mesh. As for the free external modeling software, Blender can be downloaded and used for free. If you are a student, you can acquire a student version of 3ds Max or Maya to use for non-commercial projects.

FBX Material Pipeline


Youtube has tons of free tutorial videos for all the free software modeling tools out on the market right now. Some might require a channel subscription, but the help is there. Goodluck, and let me know if you need further help.


Andrew Hurley

avatar image MS2013 Jun 26 '15 at 07:42 PM

Hey Andrew,

A quick question: As a student, I was able to acquire 3ds max 2015. So now that my level is basically modeled using bsp, do I convert these bsp into static mesh and then import them into 3ds max and modify them? or do I create them from scratch in 3ds max, using the same height and width etc and then import into ue4?

Thanks for all of your help, I really appreciate it.

avatar image AndrewHurley Jun 26 '15 at 08:54 PM

Hey MS2013,

If you would like to create custom LOD's or edit the mesh after converting your BSP's to a static mesh, you can export it from the engine and pull into into 3ds Max.

Other than making sure the faces of your BSP's have the correct scaling for the UV's, and your materials are applied correctly, you shouldn't need to do any sort of exporting to Max.

You are welcome.

Andrew Hurley

avatar image MS2013 Jul 22 '15 at 05:33 PM

Hey Andrew,

Thanks to all of your help, I was able to properly replace my use of BSP with Static Mesh and still retain the look of my level. I have expanded my level with some landscapes and the light build times are taking around 20 to 30 minutes. I have included light map importance volumes as well, and the level still takes around the same amount of time. What would be the best way to proceed in reducing that time and is there anyway I can perform level streaming even though the landscapes were all added to the same map and not as separate levels?

Thanks and looking forward to hearing back

avatar image AndrewHurley Jul 22 '15 at 05:45 PM

Hey MS2013,

Glad to hear your project is progressing. Would you mind creating a new AnswerHub post for the issue you are currently experiencing? This is done for tracking purposes so posts do not go off topic and people can easily search for a valuable answer they might need to solve their issue.

After creating the new post, you can provide me with the link in your response here, and I will be happy to take a look at it.

Thanks -

Andrew Hurley

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Hey MS2013,

Are all of the lights in your scene set to movable? Try setting them to static to see what occurs. You do have an excessive amount of lights in each wall which, I will go ahead and tell you, is going to hurt your performance.

When you convert the BSP's to static meshes you need to change the lightmap resolution of your walls and set the lightmap coordinate index correctly.

alt text

Take a look at all of these settings and be sure you are using them appropriately.

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answered Jun 02 '15 at 07:34 PM

avatar image MS2013 Jun 03 '15 at 10:56 PM

thanks Andrew. I'll take a look at these and try building the BSP as static mesh. I made the lights all static and the same error occurred.

Thanks again.

avatar image MS2013 Jun 09 '15 at 04:58 AM

Hey Andrew,

I converted all BSP to Static Mesh using the settings you provided and the UV Wrapping is all messed up and the level looks completely different than my original with BSP. I Saved a previous version which highlights what the level should look like and the current version that has the level with the converted BSP to Static Mesh. Can I please send this to you and have you take a look at it? I am completely lost and I don't want my long hours of work to go to waste due to this conversion since my level looks completely different.

Thanks and please let me know.

avatar image AndrewHurley Jun 09 '15 at 06:21 PM

Hey MS2013,

Go ahead and grab the Content, Config, and UProject folders/files and zip them into a compressed folder. Now upload it to an external file sharing like DropBox, and provide me with the link to the downloadable page.


Andrew Hurley

avatar image MS2013 Jun 17 '15 at 03:01 AM

Hey Andrew,

Here are the links to the downloads for the Content, Config, and ProjectFiles. I had to split them up since my drop box upload continued to crash when I zipped all three folders together (oddly not separately, one folder at a time). Anyways, here are the links:

Content: https://www.dropbox.com/s/bhjf9vz11pqc7qp/Content.zip?dl=0 Config: https://www.dropbox.com/s/ifyeazbavi2vomc/Config.zip?dl=0 ProjectFile: https://www.dropbox.com/s/grjbuybcaddmmas/Blueprint_LevelPract.uproject?dl=0

Thanks for the help. I really appreciate it.

*NOTE: In the Content folder you will see two maps, one labeled SciFiTest3 and SciFiOriginal. The original is the one with the converted static mesh that has the problems and the test3 is the original BSP version that has all the correct lighting that I want.

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