Lightmass generates seam

Hi all, so I am having yet another problem with lightmass. I have unwrapped my mesh to the best of my knowledge, textured it in Substance, then brought everything into UE4 and baked my lighting (static). The mesh then displays a nasty black seam along its side (where it was cut in Blender) and I cannot seem to get rid of it no matter what I do (tweaking lightmass or setting up higher lightmap res). Any idea how to get rid of the seam? Or have I done a poor job with unwrapping the mesh? (The checkboard texture seems ok.) Desperation is setting in.

try to increase lightmap resolution in the mesh settings, if not helped - decrease Static Lightining Level in the World Settings

Tried that and while increasing the lightmap res helped a bit, 512 res for a mesh in a bigger environment is just crazy. I think it has something to do with my UV map / lightmap, but don´t know where exactly the problem lies… Thanks anyway!

in that case - increase distance between UV islands on the lightmap channel, because 64 pixels may be not enough to separate them on texture

Do you mean increase the res? Because I did try going even up to 512 and the seam was still there (a bit less visible). Or do you mean manually shifting the islands on the UV map? Then I would have to make a lightmap in my external DCC I guess. It is weird though, because my other pillar doesn´t have this problem.

I mean manually. do you have one pillar, and on the scene one instance is ok, but another with the seam? if so - decrease Static Lightining Level in the World Settings (from 1 to 0.5 for example and bake light again in the production mode)

Since you are in blender. Can you go into face mode, hover over the pillar, hit L to select just those faces, and share a screenshot of the blender UV map (for the light map, should be the second channel)?
I just want to make sure the unwrap of the pillar has just the one seam along the length and not 2
You really can’t tell from the screenshots, since we don’t know if the rectangle actually corresponds to the column portion / items arent unwrapped proportionally (which is probably fine. Except I would make the UV map for the Column the tallest/biggest part of the map and shrink the rest for a slightly better result)

Also, holy vertex count. Isn’t it a bit much for a single pillar that probably won’t even need vertex painting?

Hi there and thanks for taking the time with my problem.

Yep, the pillar has only the one seam along its length and according to the checkeboard pattern it should line up nicely. As for the proportions, I wanted to keep the texel density exactly the same throughout the whole map - as I understand it, proportional TD is key when making game assets?

As for the vertex count, I tried to keep it safe to keep as much silhoutte from my high poly sculpt so that I wouldn´t get issues when baking normals later down the line - does that make sense? I am still new to this, so I guess this comes with experience.

The two screenshots you asked for are attached.alt text

Hi, thanks for that, I will definitely try it again although I did try it early on and it didn´t work.

Wouldn’t call texel density key. Normally a good material will overlay a few textures to break texturing - that said, it can be helpful.

The uv map looks alright.
The next issue could be the export type/smoothing.
Because the red seam you May have a sharp edge marked under that seam. Check that by removing all seams.
Make sure you export either seams or faces
When you import make sure to select import nortmals/mikkt
See if that makes a difference or not.

Last thing you can try is to move the Uv map off the edge. It should really not matter, but maybe it’s too close to the edge for the size you are baking.

No dice. No matter how I export it out from Blender (face smoothing, tangents and different permutations) and import it into UE4 (mikkT always, importing or computing tangents/normals), the seam is just always there when I bake the lighting. You can see from the picture that when the mesh is duplicated, the seam is invisible (with the white default mat) and barely visible with some basic material on it (the checker texture hides the seam perfectly). I just don´t know what more I can do here. I even stripped the mesh down to its basic form and rearranged the UV space so that each island has plenty of space between each other and the main island has sufficient space from the edges. Nothing helps.

Why not take a screen shot of the light build debug?
viewmode lightingonly
Or alt 6

You should do a manual step through with these to make sure you actually aren’t applying the line via something in the material

Only other thing would be to share the asset for people to verify.

It is a sole problem of the static build. As you can see from the light debug view, when in stationary mode, the seam is not there. The mesh (and the texture) looks better under stationary light too.