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Tag static parallel meshes to reduce baking seams

Hello, I'm facing the common problem where 2 static meshes with planar faces produce a seam in lightmass. I'm aware of the workaround (hiding behind another mesh, baking with crazy high setting, snapping UV isle to the pixel grid etc.) and SurfacedNormal has found the solution (exporting 2 meshes and importing as one, actually fixes the problem without using any workaround). So my question is: is there a way to tell lightmass to consider two meshes as part of the same object so it won't produce any nasty seams and I don't have to generate new unique meshes? Since it works with the exporting/importing method it's not a physical limitation of lightmass and I'm sure a solution could be easily found. Thank you.

Product Version: UE 4.11
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asked May 04 '16 at 05:19 PM in Using UE4

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2 answers: sort voted first

... You need to have a proper workflow when working with static meshes and lighting which includes proper Lightmaps, snapping to grid, etc. There is no "easy button" at this time in UE4. But as far as I know, you cannot tell lightmass to consider two different meshes the same.

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answered May 04 '16 at 05:36 PM

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avatar image JohnDoe0 May 04 '16 at 05:42 PM

I'm not asking for an "easy button" the baker is clearly broken, nothing like this would happen in Vray for example, and actually it doesn't happen even in UE if you merge the two meshes. So do you know someone who could be able to have al look into this. From what I've heard the problem is that each mesh ends up in a different thread while is being processed by lightmass.

avatar image VictorBurgos May 04 '16 at 05:49 PM

Would be easier if you had pics of what your exact issue is.

avatar image JohnDoe0 May 04 '16 at 05:50 PM

Please follow the link in the first post and go to the second page

avatar image VictorBurgos May 04 '16 at 05:56 PM

I did...what am I looking for? I don't a post from you.

avatar image JohnDoe0 May 04 '16 at 05:58 PM

That's odd, post 43#

avatar image VictorBurgos May 04 '16 at 06:00 PM

Heh, I think I may have hit next thread instead of next page. Because I definitely got to the first page, just didn't get to the right 2nd page though. Or maybe I did do it right but hit a bug. Anyway, got it.

avatar image VictorBurgos May 04 '16 at 06:03 PM

Wait a minute... are you using the exact "mesh" for different sizes in the editor? And using 2048 Lightmaps seems pretty darn silly tbh. Have you been using Lightmap Density to make sure things are good?

avatar image JohnDoe0 May 04 '16 at 06:22 PM

Yes. That is just an example where I merged all the walls together and the whole room has a 2048 LM. Ideally you would merge for example the "wall window" mesh and a standard "wall" to close the gaps. 2048 was on the high side for that specific scenario but is not the point, even a 512 comes out perfect when you merge the meshes. The point is that if a put side by side a "wall" with a "wall_window", especially if lit by indirect bounces, a seam will show up unless I export them as a single mesh and then reimport them.

avatar image JohnDoe0 May 05 '16 at 10:21 AM

Any news? Btw all scenes were in the ideal to greater than ideal texel density state.

avatar image VictorBurgos May 05 '16 at 03:30 PM

I need you to send me your project as well as the FBX you used in your scene so I can be of further help. PM me a link on the forums when you get a chance.

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After further review of the project. Meshes were not original meshes, but were StarterContent meshes. In the future, I would suggest using your own meshes, with proper lightmaps and UV texture density.

Even so seams were able to become much less visible after using the following settings under World Settings:

  • IndirectLightingSmoothness: .6 (play with this)

  • IndirectLightingQuality to 2 (play with this)

Here is more information on the current limitations of the engine in regards to this issue.

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answered May 05 '16 at 06:12 PM

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avatar image JohnDoe0 May 05 '16 at 06:20 PM

Thank you for the reply. Actually I've update the Second UV channel to snap to the pixel grid for some of those meshes and the density is on green or higher for all of them. As I posted on the forum (one of the links you posted) bumping the lightmass setting only reduces the issue. But the only way to fix it seems to merge different meshes. Thank you anyway for your time Victor!

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