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Why are my Static Meshes black even though lit?

I've been having this difficulty in my main projects, so I decided to make a small project in which to test the lighting for quicker turnover with light builds.

As you can see ( in the bottom picture ), the static meshes are all normal under preview settings, but, when the lighting is built ( in the top picture ), it turns most of the meshes black, and some, like the bookcase behind, become very splotchy.

I've seen other threads asking about this and have tried the fixes they mentioned - I generated other UV layers to make sure there was a UV layer 1 and 2, and I also reimported these meshes with the normals calculated by UE. I also tried changing the lightmap resolution, to no avail.

I'm at a loss. What am I missing?

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asked Jul 24 '14 at 07:01 PM in Rendering

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Jeul
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avatar image Jeul Jul 24 '14 at 08:21 PM

I generated the second ( and even a third ) UV channel within UE4. I get an error about the .fbx missing smoothing information on one of the items, but, seeming as it's not on all the items, I figured it was unrelated to whatever is causing this.

avatar image fighter5347 Jul 24 '14 at 08:23 PM

Create the lightmap in a 3d program and then test out if the meshes will be still black

avatar image Jeul Jul 24 '14 at 08:27 PM

I have no idea how to do that. What would the other program do that UE4 isn't capable of?

I get the distinct feeling that this is an issue with some setting with the lighting or the UV within UE4.

avatar image fighter5347 Jul 24 '14 at 08:32 PM

When you send me the file I can test it out for you -> it does the same as the UE4, but I think just in a better way (out of experience the generating in the ue4 fails most of the time)

When you like you can send it to me as a pm in the forum: https://forums.unrealengine.com/member.php?95-fighter5347

avatar image Jeul Jul 25 '14 at 03:03 AM

Sent you a PM. Thanks for helping with this.

avatar image fighter5347 Jul 25 '14 at 10:31 AM

Another thing could be that you use roughness and metallic in your material -> add a sphere reflection capture node

avatar image Jeul Jul 27 '14 at 07:41 PM

I checked the roughness and metallic settings for each material and tweaked them in a bunch of ways and it had no effect. I hadn't tried it with the sphere reflect capture node, but would that even matter if the metallic was set to 0 ( or 1, I forget which means it's not reflective )?

avatar image fighter5347 Jul 27 '14 at 08:07 PM

1 roughness -> no reflection. I would try out the way with the reflection capture actor, because I think there are just two ways why your mesh is black. Either the reflection or because of the 2nd uv channel :)

avatar image Jeul Jul 27 '14 at 08:09 PM

Alright. I see what you're saying. I tried it like you mentioned and it didn't seem to do the trick. I shot you a link to one of the models in a PM, if you still were willing to take a look at it. :)

avatar image fighter5347 Jul 27 '14 at 10:25 PM

Ok, I tried out various stuff, but somehow I can't find out what is wrong, because in my case it works -> so it must be the material or your light setup. Could you probably post a screenshot of your mat + information about the light setup? Here is a modified version of your mesh (you haven't unwrapped your model) https://drive.google.com/file/d/0Bx4rUIObSdNYbnpnNFNmMVZsanc/edit?usp=sharing alt text

table.jpg (49.7 kB)
avatar image Jeul Jul 27 '14 at 10:58 PM

Alright, I grabbed that model and looked at it, and the one glaring difference between the model I sent to you and the model you sent back is that the original had 3 materials assigned to different parts of the mesh ( one for the desktop, one for the body, and one for the legs ). The one you sent to me is comprised of only one material ( one solid UV, whatever ).

avatar image fighter5347 Jul 27 '14 at 10:59 PM

Yep, I know ^^ + it has a 2nd uv channel -> but is it still black?

avatar image Jeul Jul 27 '14 at 11:02 PM

I'm building the lighting as I type this. Will post results in one moment.

avatar image Fenrix Jul 27 '14 at 11:13 PM

so why do you have to make a second UV channel anyway? is that something you do if you didn't unwrap it without overlaps? or is this like a blender specific thing that happens? because you could always try exporting your models from blender to another program and unwrapping them in that then exporting to fbx from there.

avatar image Jeul Jul 27 '14 at 11:18 PM

I'm not sure, but it's something to do with UE4 using UV layer 2 ( or 1, as it would be ) for lighting. The problem, as far as I can tell, is that even though I used UE4's auto UV generation to make a copy of layer 0 into layer 1 ( or 2 ), it still didn't correct this issue. Not sure why.

avatar image fighter5347 Jul 27 '14 at 11:19 PM

Normally the UE4 takes the first uv channel as the lightmap layout, but sometimes those uv's are overlapping. This will cause some problems (black spots on your mesh, entire black mesh,..). Sometimes you dont have to create the lightmap, but just when the first channel follows the rules of a lightmap (no overlapping uvs). This happens with all programs, not just blender ^^ Here you can get more information about lightmaps: http://www.worldofleveldesign.com/categories/udk/udk-lightmaps-01-basics-and-important-principles-for-creating-using-lightmaps.php

avatar image Fenrix Jul 28 '14 at 12:16 AM

could be your uv's are reversed then. I use Maya and have not had this particular issue except when my normals were facing funny directions. FBX is an odd format, with all kinds of silliness happening.

avatar image fighter5347 Jul 28 '14 at 12:21 AM

I dont think that my uv's are reveresed, but I also dont have to create a 2nd uv channel for every mesh :)

avatar image Fenrix Jul 28 '14 at 07:00 AM

god, I knew I shouldnt have posted here now its happening to meeee >.<

avatar image fighter5347 Jul 28 '14 at 09:54 AM

;) But now you know the solution

avatar image Jeul Jul 27 '14 at 11:05 PM

Here ya go. Looks like it gathered the light just fine, so it's not the lighting in the scene, then, right?

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avatar image fighter5347 Jul 27 '14 at 11:07 PM

Then it's the 2nd uv channel that I created in blender ^^ -> https://www.youtube.com/watch?v=z5yc-bKbHyc (I did it the same way as in this video)

avatar image Jeul Jul 27 '14 at 11:12 PM

Alright, I kinda understand what you're saying, but not fully. I will attempt to try the steps laid out in the tutorial you linked, but can you explain to me why this problem is happening and why I can't just use the UV generator in UE4?

Again, if I haven't said so enough - thank you so much for all of this help. :)

avatar image fighter5347 Jul 27 '14 at 11:17 PM

You can use the generator in the UE4, but mostly you dont get a good result ^^ So it's recommended to do it in a 3d program (my way which is shown in the video isn't the best way, but you will have a good result in the end + it's really easy) Here is the theory behind 2nd uv channels + lightmap: http://www.worldofleveldesign.com/categories/udk/udk-lightmaps-01-basics-and-important-principles-for-creating-using-lightmaps.php

avatar image TorQueMoD Nov 04 '14 at 06:06 AM

So I had this issue for ages and couldn't figure out what was wrong because my meshes weren't lighting correctly even though I had created a secondary UV. Tim Hobson from Epic told me how to fix it. Here's what he said:

In the Mesh Viewer in UE4 make sure that you're got the lightmap coordinate set to 1 instead of 0. This will be located in the details panel to the right.

Hopefully that's your issue.

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Have you generated the 2nd uv channel in the UE4 or outside in a 3d program? + do you get any errors when you build the light?

Because normally this should be solved with a 2nd uv channel + proper lightmap :)

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answered Jul 24 '14 at 07:34 PM

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fighter5347
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Have you tried changing the Light Map Resolution AND changing Light Map Coordinate Index? That's what works for me when this happens. Change the Light Map Resolution to 512 and set Light Map Coordinate Index to 1. https://learnunrealengine.com/fix-mesh-turning-black-issue-ue4-geometry-brush-converted-static-mesh-turns-black-building-lighting/

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answered Mar 26 '17 at 01:47 AM

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godmachine33
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