Home Technical Talk

Question regarding UV unwrapping and Smoothing Groups

polycounter lvl 4
Offline / Send Message
DustyShinigami polycounter lvl 4


Just a quick question regarding UV uwrapping and Smoothing Groups: we were taught to add Smoothing Groups FIRST before UV unwrapping. Is it perfectly fine to do it backwards instead? Are there any negative downsides to doing that?

This is just a personal preference for me, doing it backwards, but I find it easier as I can add my cuts and make my UV islands, and then I can more easily select them in Max, and from there - add a Smoothing Group. :)



  • Ghogiel
    Offline / Send Message
    Ghogiel greentooth

    It's usually done the other way because, as a general rule, you want to set up the shading before moving onto UVs> you might need to change geometry if the shading isn't great. But you can pretty much predict if something is going to be an issue if you have a little experience.

    The only other reason I can think of would be is you have marginally more/better tools make face selections for smoothing groups than to select make seam edges. Especially if the geometry isn't quaded loops. You can just hit the explode by smoothing groups and you probably are close having the islands you need in many cases.

    I don't think most of time it's not going to make much of a difference, kinda a minor workflow prefernce.

  • DustyShinigami
    Offline / Send Message
    DustyShinigami polycounter lvl 4

    Hmm. Okay. I forgot about the explode by Smoothing Groups option. Though I usually quite enjoy unwrapping in Maya thanks to its distortion checker, even if it means having to manually add seams etc., then once I’m happy, I export the mesh back out into Max. 😁

    I have been making sure to have quadded loops with my current model, but there are some areas where face selecting is a bit of a pain, even with the Grow and Angle selections. I made sure to add the quadded loops/edges around the parameter of some areas, knowing that’s where I would add my seams/cuts.

    I think, in the case of the model I’m working on, I kinda knew beforehand how many Smoothing Groups I was going to need per mesh. Some I decided to change slightly, once I was adding cuts, and realised I’d be better having a mesh with two separate islands/UVs, but the majority have only needed a single Smoothing Group as they’ve not needed any hard edges.

  • sprunghunt
    Offline / Send Message
    sprunghunt polycounter

    I UV map first all the time. Smoothing groups cause splits in the geometry. Splits mean more vertexes and therefore more memory.

    So in order to make sure my meshes are as optimized as possible I will do this:

    1) UV model

    2) setup hard edges/smoothing groups wherever there are UV splits (I always try to reduce the number of UV splits while avoiding causing too much distortion)

    3) do a test bake in substance designer

    4) add extra smoothing groups if there are any visible artifacts

    5) bake model again

    In my experience this ensures the most efficient models.

  • Bolovorix
    Offline / Send Message
    Bolovorix sublime tool

    In order to get clean bakes in the engine I work in I pretty much have to setup smoothing groups based on UV shells. So I always UV my models first and then setup smoothing groups based on the UVs.

    I use a custom script to do it in Max and am not sure what tools it has out of the box, but, in Maya if you select all of your shells you can convert selection to shell border and in blender I just make sure all my UVs have their seams marked and I do a "select similar" by "seam" and set those edges to sharp.

  • Kanni3d
    Offline / Send Message
    Kanni3d ngon master

    Shading/smoothing groups first, then base those shading/smoothing splits onto your uv splits (which you can then split further if needed).

    I find that if you do UVs first, and run a script to gen smoothing groups from UV's, you'll come out with not optimal/desired shading.

Sign In or Register to comment.