Trim Sheet Lighting Issue

HixaLupa

Hey there, I've spent days creating some Ancient Greek trim sheets for a uni project but now in UE4 they're baking super weird. It's as if UE4 is doing the lighting for 1 object then just giving that bake to all the others- it looks horrendous!

Lightmaps are green, but the UVs look like this (this is only one sheet, each object uses 2 sheets)

Perhaps its the overhanging and overlapping UVs but I don't see a way to avoid that without texturing the damn thing on it's own.

If anybody can 'enlighten' me lmao that'd be awesome. Everything looked ok until it randomly changed the previewed lighting and now it looks this way and my deadline to show the sheets in action is tomorrow (13th)

Used Maya, Painter and UE4 obvs

HixaLupa

For some reason when it's rotated the roof behaves fine, but flat it does this.

I thought perhaps it was the high Sun but it does it whatever angle it's placed at around the UE4 Z axis.

Obscura

Looks like you have 1 smoothing group over the whole object.

leleuxart

Like Obscura said, check your vertex normals/smoothing groups and make sure your normal map is also in the correct format and used properly in the material. You're not rotating the normal map in the material either, right?

Obscura

Are you maybe using a secondary uv channel for the trim normals? I'm asking because Unreal does not create tangents for the second channel by default, which can lead to wrong shading.

oraeles77

yeah, I aint an expert on Unreal, but I was actually thinking about this scenario yesterday, cause I made a lowpoly fence and after re-baking the lighting it in Unreal, the fence is now black, obviously because I repeated the same textures/trim tiled (however you want to describe it) and exported it with only 1 uv set.

I'd assume there's a tick box on the importing options box regarding 'generate lightmap uv' .

Lightmaping refers to a UV layout which will be used for light baking and stuff like that.

so if you are doing a trim tiled model while it looks nice in a rendered scene in Maya, or Sketchup or Blender or whatever, if you are exporting to a game engine you must consider the UVs.

usually the last UV in the list (I think 8 is the max) will be allocated for lightmapping. but you can also use that UV for other things if you want.

let me know if my advice makes sense or helps out.