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enter image description here We have a 3D model in ZBrush and we extract the UV map from it. Exporting it in SubstancePainter and trying to set the textures however , leaves white spots in some places. I have seen that depending on the size of the UV Map the white spots appear in different areas. What could the reason for this behaviour be? Computer Graphic Perspective , what is the reason for this problem and what would be a good idea to overtake , in order to fix it ? enter image description here

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  • You probably should ask on a Zbrush/GameArt forum: I don't think you'll find a lot of Zbrush users on Graphic Design Exchange. And you probably should show the UV map because it's impossible to say. My guess is islands are too close to each other? But I'm speculating – Sergey Kritskiy Dec 3 '20 at 19:22
  • I asked it in Stack overflow and they sended me here . Of course I will share some pics too ... my bad ! Pictures Added ! Everything else looks perfect , this little spot is the problem . – Ivailo Manolov Dec 3 '20 at 19:49
  • oh geez, what do they know at Stack Overflow... – Sergey Kritskiy Dec 3 '20 at 20:28
  • Thank you :) I like StackExcahnge's community far better ! – Ivailo Manolov Dec 4 '20 at 10:13
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First of all, you might use something like ShareX to easily screenshots and screencasts: it's better than taking photos of your screen;

Next, to my knowledge Zbrush UV Master doesn't provide production-quality UV maps, it's more like a starting point — and mostly for organic models. With hardsurface models generally you want for straight edges of a model to be straight on the UV. This is the first issue with this generated UV — all straight UV islands are rotated which will create weird looking artefacts on lower resolution textures.

Second issue comes from the first one: generally you want UVs to be packed as tight as possible to not waste image space and because your long straight islands are rotated, there's a lot of wasted space which means that you have to have an image of higher resolution to achieve a decent result.

And the third issue comes from the way ZBrush packed the islands. UV islands should always have a bit of space between them (called edge padding) because when the texture is downsampled, pixels around the UV island will start to bleed in these islands. Here's a good explanation of what's happening, I'm going to paste just one image from this Polygon artice:

enter image description here

A 512x512 texture with no edge padding. White pixels are the used areas (shells), black pixels are the unused parts (gutters), and the UV shapes are shown in pink. As the texture is downsampled, pixels from the gutters bleed into the shells.

To sum up. You have them like this:

enter image description here

But you need them like this:

enter image description here

What to do? Use a different tool for UVs. From a free Blender to a popular standalone RizomUV.

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  • OMG !!! This is sooooo useful !!!!! Never have I ever received such a detailed and high quality answer. Usually in StackOverflow my posts get closed , with no explanation , and when they dont , I get answers like " Check here ......... like they are thinking I havent checked and just asked blindly"... StackExchange's community is 1000 times better. Thank you for your great answer , totally logical . – Ivailo Manolov Dec 4 '20 at 10:12
  • @IvailoManolov well, StackOverflow is for coding questions, so I can see why. Anyway, if my answer answers your question please don't forget to accept it using a ✔️-mark – Sergey Kritskiy Dec 4 '20 at 20:20

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