My question is about seams. As of my underestanding if you are going to texture in a 3d program then you just need unwraped UVs even if they are divided in 1000 islands it doesn't matter. Is it true? I see some people still care about seams even if they are texturing in a 3d program. Because i want to split a human's body…
Seams will not matter at all in Arnold. You should look into using layered shaders with multiple UV's and projected textures. You can also use 3D textures like the solidfractal node. But that's a completely different style of creating textures to games. You should probably ask these questions on forums like CGtalk or…
What are you rendering in? For offline rendering there's a bunch of texturing and UV techniques that you can use that have nothing to do with realtime rendering.
"divided in 1000 islands it doesn't matter." It does matter because you are creating extra vertices. Seams can also appear along UV cuts from mip mapping the textures.
You can choose auto unwrap in most programs. That creates uvs only your computer can read and edit. Its general practice to put island seams in the least noticeable place on a model. Painting in a 3d app should be seamless. No idea what you want to do to increase the texture resolution of your model.