I'm trying to texture a sphere (a planet to be precise) using a number of different tiles. Initially, the sphere is broken into 8 pieces, then each piece into 4 pieces, giving a total of 32 pieces. (The reason I'm doing this is I'm taking it into Unity, which only supports maximum texture sizes of 4096x4096, and I need it to be very hi-res, so each tile is 4096x4096).
To get each piece of the texture into place (and this is the case if I use selections on one whole sphere, or actually break the sphere into separate pieces), I have to tile each texture: 8 tiles on U, 4 tiles on V.
The problem is that this leaves seams around the edges of each piece - although the tiling and proportions should mean that what is displayed is exactly one tile, a few pixels are stretching over.
I don't understand why this is happening. I can get the extra pixels to disappear by fiddling with minuscule changes to offset and length-U and length-V, but it messes up the alignment subtly but visibly.
Does anyone know how I might get around this?
Or a better way to accomplish what I'm trying to do?!