okay so...those of us who create alot of uvs generally output the map at the usual resolutions of 1024, 2048 and 4096 from the uv snapshot menu, but how many of you think about the resolution of the map in the first place in accordance to the uv grid?? I know I didnt.
Well since I was introduced to this little nugget a little while ago Ive since really considered the way I output my uv's from maya before heading into painting them.
What you want to achieve or for a better word is avoid bleeding between the uv shells.
So here in Image 1 we have the standard and default settings of the editor prior to output of a uv map. I've use two cubes as an example.
Okay so heres the cool bit. Lets say you want to output a 2048 map of your uvs and you need to make sure you have a good amount of room between the shells. Simply adjust the Subdivision slider to two pixels less than the output, in this case it will be 2046. This number allows for cut off of 2 pixels that are actually your grids edges. Also check the subdivisons line radio box and put the other two sliders to 1 for now just to keep it simple as we are not creating multiple uv maps.
So then by zooming into the shells you can see how many pixels are going to be between each shell once in PS or Zbrush. and if you feel they are too close then you can move them. from a map of 2048 I would suggest judging the distance you feel comfortable and is adequate enough as in Image 2 to give you ample enough room for any occuring bleed that may happen.
try putting in 1022 on the subdivisions for a 1024 map and watch how the grid spacing differs, again you can then judge the distance again before outputing to a 1024 map.
and also a 4k map. Note how the pixel spacing increases and decreases on both the new settings, so its time to move those shells in either direction to avoid the bleeding areas.
hope this helps