faceting in lightmaps

I’ve run into this a couple times, and never figured it out: the problem is, I’m getting some faceting artifacts in the lightmaps of certain meshes. I’ve triple-checked the meshes, and they have all of their UV’s stitched, edges softened, their lightmaps are reeeally high-res, and I’ve been careful to import with their normals intact. In fact, as you can see in the last image, they even display correctly in the asset editor, but when I bake they get all this junk in there. I’ve tried turning up a the “Indirect Lighting Smoothness” a little, in world settings, but it didn’t seem to do anything. Anyone have any ideas what I’m looking at?

Is your tangent basis correct, too?

i tried importing with the third option “normals and tangents,” instead of just “import with normals,” but it didn’t seem to make a difference - not clear on what the difference is; I thought your tangents were always perpendicular to your normals, and oriented via the UVs (or something)? so theoretically, it shouldn’t make a difference if i let Maya or Unreal calculate them, right; at least, it didn’t seem to.

UPDATE: after talking to a couple people, it looks like this could actually be described as a by-product of having my lightmaps TOO high…? Which confuses me. Lower lightmaps certainly obscure the problem areas here, but what if you need more resolution in order to resolve light bleeding, or pixelated light cuts…? As I mentioned, I’d really expect the “indirect lighting smoothness” setting to have an effect here, but it didn’t seem to. Are there other settings I could be missing that would help with this interpolation?

Well what I see is a typical smoothing group problem of objects that do not have any smoothing groups assigned or the object was not welded in the host app.

In UE4 you should have at least 1 smoothing group so in what ever app your using make sure that included smoothing groups is checked

Hi Frankie, thanks: am I right in thinking that “smoothing groups” is simply how Max users and the like refer to what we in the Maya world would call hard/soft edges? If so, like I said, all edges are softened (and locked/unlocked, transferred, hardened and re-smoothed and re-smoothed to make sure, and then to make TRIPLE sure it’s not the mesh…) and sewn in both the texture UV’s and the lightmaps. It was exported with smoothing groups checked in the FBX exporter, and lights normally in other circumstances. Actually, it was pointed out to me that similar problems show up in the GI of even the starter content’s example assets, when you crank their lightmap resolution really high. Curious.

As in this?

Then yes hard/soft edges in Maya can be though of as being a form of smoothing but is not a smoothing group in the way 3ds Max does it and as expected by Unreal 4.

It should also be noted that smoothing groups can become rather fragile where it becomes next to impossible for the object to even accept and maintain the grouping as expected.

A some what know cause is extensive editing of an object can can do nasty things to geometry surfacing in 3ds Max that you can not see in the view port so at some point you might have to rebuild the object from scratch.

As I mentioned though you could test by flipping switch’s in the export/import process but it’s been my experience that once the SG’s are bonked you might as well rebuild.

P.S. It should also be noted that re-importing a object that you think has been fixed does not import the edits and it “seems” to me that a re-import does not always included changes to the SG’s so best practice always delete the current object and import a clean from scratch version.

Do you have any dynamic shadows in your scene? I’ve ran into a similar problem before but it was with a dynamic lighting setup. I had to either reduce the number of dynamic shadow cascades or increase the shadow casting distance on the directional light. Also changing the shadow bias helped too.