Problems painting textures in ZBrush and importing back

[Bangari]

I am trying to use ZBrush to paint texture on to models that have been exported out of Lightwave and then re-importing them back into Lightwave. The test object is simple table that is made of only rectangles.

I am using masking to conceal parts of the table in edit mode previous to "dropping" them onto the canvas in ZBrush, and Projection Master has the "FADE" option turned off, and normally turned off "double-sided" option as well, when I try to paint only one side of an object. I usually put the texture size to 1024 x 1024, I have also tried 2048X2048. For painting I usually use single layer brush with a solid square Alpha, and a drag rectangle stroke with the RGB intensity set to a hundred.

The problem I face is that after painting textures in ZBrush, by the time I import the model in Lightwave and then apply the texture to what I can see the colors "bleed" to other parts of the model that I have saved at the time of the painting, and also fading of colors can also be seen around the edges of the rectangle, even though I turned off FADE function from the projection master. I am having problem in painting textures for ZBrush and importing back

[Eric B]

Try to create UV maps first in Lightwave before exporting them as the part of .OBJ file or try to create them in ZBrush through AUVTiles or GUVTiles. Try to use ZBrush for texturing, but had to give up because ZBrush's UV mapping was not accurate enough. Try to use these solution I hope this may help you. If you are facing any further problem then give a detail information about it.

[Bangari]

Thanks for the suggestion; I have tried it but absolutely no effect. I think that there is a problem with the way Lightwave interpolates its UV coordinates compare to the way ZBrush does, may be it is due to some kind of “rounding” errors. The thing you have said about the ZBrush's UV mapping not being accurate is correct. If you have any other solutions then please reply.

[Glenny]

According to ZBrush coordinates are perfect and accurate. In most of the cases, it looks and bleeds because of the differences in the way that a variety of programs interpolate UV coordinates.

In such cases UV coordinates may need to be shifted by 0.5 pixels to the different position such as left/right/up/down for achieving the perfect registration.

[JonathanD]

Follow these simple steps for getting rid of your problem:
1. First import the mesh in to ZBrush
2. After that import the texture or it will be better to create a new texture with the same dimensions that you will use in your other application.
3. This will allow ZBrush to calculate the perfect value for which it will result in an 0.5 pixel offset.
4. After that adjust the AdjU and AdjV in the Tool > Texture menu and then press Apply UV Offset.
5. Until you get the correct offset repeat the steps 2, 3, and 4.
This will surely resolve your problem.

[Bangari]

I was able to get rid of bleeding and changed surface structures. But the only way I could do was to educate UV Edit Pro and scale down UV tiles after object was imported back into Lightwave. I just could not get ZBrush to completely do the job, although I tweaked down to one tenth (0.1) of a pixel adjustment using AdjU and AdjV.

Not sure if is worth your ZBrush if I have to edit every single UV tile every time I import a model back to "Lightwave".

[Christina 80]

I think the problem is your UV map is not a high enough resolution to get the hard edges you need! The only way you could probably achieve this with a 'low-res' bitmap is to space the polygons in the UV map, so there is a gap between them. In this way, the point where you go from one color to the next on bitmap is not where you go from one polygon to another. Actually, if I were you, I would do the above, but then instead of bringing the model in ZBrush, I would just take your UV layout in Photoshop and paint it in there!