For example I have a building to unwrap, i use smart uv project and in the resulting uv map the UV Island for the roof is too large and I can scale it down. after scaling it down how can I make the rest fill up the newly created space? I tried using the "pin" option on the scaled down roof uv island, then clicked smart uv project again, but that doesn't work. Is there any way to automatically make it fill up the new space? Thanks!