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black rips and triangles in all static meshes after lighting build

Hi there, I am having huge problems building lighting in UE4. I get artifacts all over the static meshes, they seem to be rips or black triangles. It doesn't matter whether there is a texture on the model or not, they are there regardless. The models are all photogrammetry sourced but have had their lightmaps generated in UE4 at 2048 res. I have tried almost all iterations of the rebuild settings in the static mesh editor but cannot seem to get rid of the black triangles unless I go completely dynamic lighting which I would prefer not to do. Please help, as I am going nuts trying to figure this one out! alt text

Product Version: UE 4.16
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untitled-1.jpg (118.5 kB)
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asked Oct 18 '17 at 12:09 PM in Rendering

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Medusam
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avatar image Medusam Oct 18 '17 at 07:48 PM

Here it is in the viewport after a lighting build: alt text

and here in the Static Mesh editor with dynamic lights...

alt text

untitled-1.jpg (100.4 kB)
untitled-2.jpg (104.9 kB)
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2 answers: sort voted first

Commonly, it is caused by improper UV layout for lightmapping. Make sure your UV channel 1 contains a proper unwrap,without any overlaps.

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answered Oct 18 '17 at 12:28 PM

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Deathrey
7.8k 130 30 292

avatar image Medusam Oct 18 '17 at 12:41 PM

Hey, Thanks for the quick response. I am not getting any warnings about overlapping UVs in the editor and the UVs for the second channel (lightmap channel) were created via UE4 at 2048 with high precision everything. Would I expect issues still?

avatar image Deathrey Oct 18 '17 at 05:30 PM

Quite possible that more info is needed to help you. Post wireframe of your mesh, as well as shots of both UV layouts.

avatar image Medusam Oct 18 '17 at 06:48 PM

Hey, Thanks for helping out on this. Below are some screen shotalt texts of wireframes from Maya and UE4 plus the Texture UVs from Maya and the lightmap channel from UE4. The textures are 6 UDIM tiles of 8k each.

wireframem.jpg (1.3 MB)
wireframeue4.jpg (471.1 kB)
lightmapuv.jpg (340.1 kB)
uvm.jpg (210.3 kB)
avatar image Deathrey Oct 18 '17 at 07:15 PM

Thing is.. that with such density of the mesh, certain effects might take place. The size of your triangles might actually approach limits of precision of UVs, so light mapping might regard some of them as having zero surface area. Whatever the underlying cause is, I would not expect to get any kind of correct light bake with that kind of mesh.

avatar image Medusam Oct 18 '17 at 07:20 PM

so reduce further? The original was 140M, this one is 1.8M. What size is good to keep the triangle size above UV precision?

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Normals of your Model Pointing the wrong direction?

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answered Oct 18 '17 at 01:49 PM

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Nachtmahr
6.9k 143 26 172

avatar image Medusam Oct 18 '17 at 01:51 PM

Thats interesting, I will look now. How is it best to see this? In unreal or modelling software? Also, how to change the direction if that is the answer?'

avatar image Nachtmahr Oct 18 '17 at 02:25 PM

Best way is to look at them in your 3D modeling Application (google it up how to show them for your Application). Changing them is only possible inside a 3D Application. They should all face outwards so they are recognized as front faceing and not backfacing. Here some random google image as example: http://help.autodesk.com/cloudhelp/2015/ENU/MayaLT/images/GUID-AA348888-CF07-4154-BCD2-D1CED0329B57.png

avatar image Medusam Oct 18 '17 at 03:26 PM

Hi, Thanks for the suggestions so far. I have checked normals in Maya and all seems well or at least, nothing obvious wrong. i have conformed anyway and re-imported to UE4 but to no avail. Still the same problem. Am pulling my hair out!

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Hi!

I'd say the padding is too low in your lightmap and you could get light/shadow bleeds... Also another idea: have you tried 2 sided material /if it's a problem with normals maybe.../

Good luck! :)

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answered Nov 08 '17 at 04:32 PM

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Makigirl
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avatar image Medusam Nov 08 '17 at 06:25 PM

Hey Makigirl,

Thanks for the help, both good ideas. Unfortunately it is still the same after the build. I have upped the lightmap resolution to 2048 in both the lightmass settings and the build settings as I believe that is the only way to change padding in UE4 generated lightmap UV's? I also ticked the 2-sided material option for the material but still no luck. Any other suggestions would be very welcome.

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