Smoothing issue with static meshes from Blender

I have been searching online for over a day and trying a heap of different settings and fixes to solve this issue, but unfortunately my lack of understanding/knowledge about smoothing/normals must be giving me trouble. There seems to be plenty of posts about similar issues but nothing seems to be a fix for me.

I have made a high poly sculpt of a large rock, followed by a retopo into lower poly ready for UE4. I then export the low poly from blender as an FBX with the model set to smooth shading (which looks perfect in blender and mudbox) but every time I bring the low poly mesh into UE4 many of the faces show up as hard edges clearly even when smoothed. Picture below of the faces showing up everywhere, plus an image of the wireframe. The images are examples without lightmapping. It is just as bad when lightmapped.

The mesh has a UVs for texture and lightmaps, is triangulated, I export with faces set to smooth to avoid the smoothing groups error. Is there anything I could be missing that can help me fix this issue and get true smooth shading? The mesh is quite large and is has a reasonably poly count to be large (I have based it on settings from the unreal demo projects) and I would like to be able to use it at it’s large size without these faces showing up all over it.

I have also noticed that in blender the mesh has around 3000 verts, but 20,000 when it comes into unreal. The faces don’t change though. I’m not really sure why this is?

Would really appreciate any help and suggestions as this issue is throwing me behind on a pretty tight schedule.

Hi there!

If Unreal is seeing 20K verts when the mesh only has around 3000 my guess would be that you don’t have you verts all welded in Blender. Beyond that, it sounds like you probably also have a 2 or more UV sets.

Any time a mesh has split UVs, new verts are created. Any time a mesh has a hard edge, new verts are created. It looks to me like you should just run a weld operation on your mesh in Blender, re export, and re import to Unreal. I bet you you’ll be good as gold.

Best of luck

Thanks for your response! Sorry for the delayed reply. I did see your message but had been so busy over the last week.

There was an issue with the UVs that caused the masses of verts. So thanks for the tip! Also the vertices were already welded in blender.

Each face showing up when close to the meshes is still an issue, but it actually even happens with rock meshes without materials in the unreal demo scenes too. I think it really is only an issue when you are super super close or decent materials aren’t applied. Didn’t realise that the issue is barely visible in game, I was just fussing in the editor a bit too much probably!

The rocks turned out quite well in the end: https://twitter.com/AndrewJFreeth/status/597763133889912832

Thanks again for your reply. Wasn’t expecting one really.

Looks good! Glad you got it working. Be sure to mark the answer if you are satisfied with it.

This is a very interesting issue. I tried doing this myself as well, and it turns out, Blender just seems to have issues with normals. I exported a simple sphere from maya, and it imported fine without the weird normals showing up at all. Very strange indeed! I’m also not really sure what causes it, but haven’t had the time to really dig into it either. Hope your stuff is working well!

Certainly looking forward to some better support for blender to unreal in the future. Maya has an awful hefty price tag, though the tools would be great. Thanks for your help!

Blender > Substance Painter > Unreal.