Seams between modular pieces - how to avoid?

I exported my chunked terrain from Blender to UE4. Without static lighting built it has no seams (doesn’t have seams in Blender either, as I transferred vertex normals from original mesh to the chunks).

However, after building lightmaps, I get seams :confused:

ue4_terrain_seams.png
Full: https://s32.postimg.org/avviql46b/ue4_terrain_seams.png

When I export into FBX, I use Tangent Space and Normals only options in the FBX exporter.

When I import FBX into UE4, I use Import Tangents and Normals option.

Normal map was baked before cutting terrain mesh in Blender (high poly to low poly bake, then I chopped up low poly mesh).

How can I make sure there are no seams after building lighting in UE4 ?

Thanks

Did you create a lightmap for the model too?

Did you delete the history (not sure what its called in blender) of your model before importing it in?

are you rotate the normal of the vertex in blender to follow the plane??

Try bumping up the light map resolution a bit or moving the seam to a better place.

No, lightmap is baked in UE4.

Modifiers (of that’s what you mean by history) are applied on export (FBX exporter has such option - Blender applies Modifiers, then exports)

Can’t rotate individual vertex normals (plus that would be nut job - there are thousands vertices bordering each other).

That’s why I transfer normals from non-split mesh to chopped mesh using modifier. Without it I can see seams in Blender clearly.

Can’t move seams - mesh chopped using 4x4 grid to split it into chunks roughly same in size.

I was thinking about bumping up resolution, but initially I had 1024x1024 for uncut terrain mesh. So I figured that divided by 16 pieces yields 64x64 lightmap per chunk. Perhaps I got it all wrong with such calculations? :o

256x256 is 1/16 of 1024x1024.

1024x1024=1,048,576 pixels
/16= 65,536 The square root of that is 256.

or

256x256 x16= 1,048,576 pixels

Duh, silly me… I simply divided 1024 by 16 and called it a day :o (I should have just divide it by 4 instead). Thanks.

I’ll try re-building it with 256x256 resolution. I wish there was a way to transfer lightmap from continuous terrain model to the chopped one. I guess I can bake it in Blender and multiply in the material, if baking in UE4 with higher res fails to remove seams.