if it isn’t lightmaps, you might need to check your normals in blender. Maya has the option to unify all normals/set them to the same as the face normal, perhaps Blender can do something similar…Otherwise you should probably post your FBX file so that either one of us or somebody from Epic can try to repro.
Sounds good! But did the UDK version just generate your UV maps for you?
I don’t think you can do that in blender. Is it possible to do that in UE4?
Well when using the UDK one, the shadow is really blocky…
I don’t think you can copy duplicate UVs in Blender
I tried that and then re-imported it into UE4 but still the lighting was messed up. Thanks for your suggestions though!
Thank you for your help and I’ll continue to try this with Blender. It might be I’m doing something wrong. Thanks!
Increase the lightmap resolution
This problem looks like a combination of a lot of issues caused by a lack of holistic knowledge about the UE4 editor and Blender. Let’s start with Blender.
In Blender:
(Assuming you have your model unwrapped and textured, and have not yet made a second UV channel for your lightmaps)
In order to create a new UV channel, select your object and go into edit mode. Under the Object Data tab (the icon that looks like a three-vert triangle) scroll down until you see the ‘UV maps’ section. You should see one line there called ‘UVMap’, and a plus/minus sign off to the right of that box.
Hit the plus sign, this will duplicate your current UV unwrap and assign it to the second UV channel. In order to edit your different UV maps you must select the UV channel in this box.
If you have used seams to unwrap your model then you can simply re-unwrap your mesh (with your second UV channel selected) and blender will place all your islands with no overlap into your lightmap UV channel. As everyone has been saying, it’s important that there are NO overlaps in this UV channel, and it is also important that you allow a bit of padding (setting the ‘margin’ in the unwrap settings helps with that).
In UE4:
When you import your mesh into UE4 you may still need to tell the editor to use your second UV channel. Import your mesh and double click it to open the mesh editor. Find the Lightmap co-ordinate index in the mesh properties and set it to ‘1’ (your texture UV channel is the first channel - channel 0, and your lightmap is the second channel - channel 1).
If you still get some seams, try increasing the resolution of your lightmap, also found in the mesh settings.
for more reading check this out: Understanding Lightmapping in Unreal Engine | Unreal Engine 5.2 Documentation
this worked for me !
EDIT: just kidding, as soon as i rebuild the problem reappears…
This totally worked! Thank you!