Heh. *Mostly* confusing.
I understand the concept of seams but I really don't know when I need to *make* an edge a seam. I haven't done it.
The bit about joining textures--I can take two textures and join them in GIMP or whatever--but I suspect that's not what you're talking about there, is it?
Making a seam is easy, select an edge where you want the "cut" to appear, (it helps to think of unfolding it like paper), then CTRL+E pulls up the edge menu, select "mark seam". you can shift+click or ctrl+click to select multiple edges to mark as seams.
No, what I did was, in edit mode, select the "yellow" material, go into vertext paint, assign it a colour, switch back to edit mode, deselect the yellow, select the "tank" material, go into vertex paint, assign that a different colour. This ensures both are distinct in SP using an ID map, (which is created based on the vertex colours in Blender).
I then selected both those materials and assigned them to "yellow" and renamed that "yellow and tank". In object mode, I deleted the, now unused, "tank" material. In edit mode then, I an make better use of the UV map space, rather than having 2 textures which are mainly empty.
