Normals + UVW

[HornyRhino]

Hi i was reading up on Normal maps and i am just posting here to see if i got it straight if not then please correct me. Thanks so basically

http://poopinmymouth.com/process/tips/smoothing_groups.jpg

When ever the smoothing is like the bottom plane with the green lines coming out that means that in unwrapping it it goes separate? or can it stay all on the same UVW island? if so when should i break up the UV's? thanks sorry noob question could have found it else were but wanted to get professionals direct opinion. thanks again

[Noors]

You should break your uv's whenever you have a hard edge. An edge is hard because the vertex normals are splitted, which correspond to the next to last plane, in light blue.
On the last plane, the normals are averaged : there's only one smoothing group. You don't need to break the uv's.