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ZBrush - Normal Map Generation - Clarify if this is usual behaviour please

Ricky
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Ricky polycounter lvl 12
Are these exports working as they should? And if so, how on earth do I get around this issue??

Each map has another checkbox in ZBrush's normal map export box, checked. The best result is the 1st image (top left). It has perfect shading, but has one huge flaw: the normals don't go to the UV island borders because 'smooth Uvs' is checked in the options.
Turn this off, and everything goes to sh*t. Just turning it off corrects the issue, but causes another one. The next image along shows that there is a faceted effect happening on parts of the mesh, which show up very well on the model. No idea why this is happening, and it seems to make no sense....
The bottom image shows without Smooth low-poly normals, and is obviously all faceted as you'd expect I guess, though not sure why this is an option someone would want to uncheck?


I need the map to take up the entire UV island space, but look perfectly smooth as the 1st image shows. How do I do this, because it seems no amount and messing around is working. I even tried with 'Suv' in the geometry tab turned off (Smooth UVs), thinking maybe if the UVs there aren't smooth, and I then don't have the UVs on export smoothed, it would fix the horrible, random facets. - Wrong.

It seems in the past I just accepted this, and corrected the issue in Photoshop, but surely this isn't how you're supposed to do it, right?

I know I can download the lowest sub-div mesh from ZBrush too, and that will have the 'correct' UVs, this eliminating the problem, but then the UVs are messed up, especially when it comes to long, thin bits of geometry. 

Please help!
Thanks
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  • FourtyNights
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    FourtyNights polycounter
    First of all, you should never "bake" a normal map in Zbrush for your low poly model. Zbrush doesn't understand smoothing groups or a mikktspace tangent basis. You'll be better off exporting the low poly head with one (1) smoothing group and UVs from a proper 3D software such as Max, Maya, Modo or Blender - and bake it in another 3rd party baker such as xNormal, Marmoset Toolbag 3, Substance Painter 2 etc.
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  • Ricky
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    Ricky polycounter lvl 12
    FourtyNights said:
    First of all, you should never "bake" a normal map in Zbrush for your low poly model. Zbrush doesn't understand smoothing groups or a mikktspace tangent basis. You'll be better off exporting the low poly head with one (1) smoothing group and UVs from a proper 3D software such as Max, Maya, Modo or Blender - and bake it in another 3rd party baker such as xNormal, Marmoset Toolbag 3, Substance Painter 2 etc.
    The model was originally made in Maya and is all soft normals, so ZBrush doesn't seem to need to worry about that so much for this project. I've seen plenty of artists export normal maps from ZBrush for objects and characters. I do also have xNormal on my PC, so would using that fix this issue instead then? I'm still not fully sure why people use xNormal over ZBrush when all the tools are right there to do the same thing for most cases to me. I understand hard-surface models its better to have an application that understands normals from your low poly and such though.

    All I want to do is get smooth results on the normal map, but with a map that covers the UV island entirely. It seems if I turn of 'Smooth UVs' in the normal map panel, it works as it should, but then gets artefact on the map in random areas. This is what I'm trying to get past.
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  • battlecow
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    battlecow polycounter lvl 12
    If I recall correctly you have to activate smooth lowres normals(Snormals) and  smoothUVs in the normal map tab in Tools.
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  • Ricky
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    Ricky polycounter lvl 12
    battlecow said:
    If I recall correctly you have to activate smooth lowres normals(Snormals) and  smoothUVs in the normal map tab in Tools.
    Yes, this produces the result I get in the top left of the image. It has the best quality, but does not reach the edges of my UV islands. Surely this isn't correct because it essentially means I have to Photoshop the normal map afterwards to make it fit properly. It also seems that exporting the level 0 mesh from ZBrush with its new 'destroyed' UVs from being smoothed, still doesn't solve the issue as I thought it would, because the UVs used to bake the textures seem to be smoothed even more than those UVs of the model. I guess this is from 'Suv' being checked in the Geometry tab before sculpting, and then the 'Smooth UVs' being checked in the normal map generation, so the UVs are being smoothed twice?
    It says on Pixologic's site that the 'Smooth UVs' option in the normal map palette only smooths the interior of the UVs, leaving the borders where they are, but this is definitely not the case.
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  • Ricky
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    Ricky polycounter lvl 12
    Ok so simply exporting high res meshes and low res then using xNormal has fixed like 90% of the problem. Why? The maps now all go right to the UV edges like they should, apart from in a few areas but I understand why in those cases, which is down the way I modelled some things. Still not sure why ZBrush had an issue with this though and it irritates me not knowing what was going wrong -.-
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