Straightening

You can straighten UV islands extremely quickly in UV Flow, in both the 3D View (Cut UV tool settings) and the UV Editor (UV menu). It’s context sensetive and which operation it performs is based on what you select. You can even straighten multiple islands at the same time!

If you select a single edge, straightening will rotate the island so that the edge is aligned to the nearest axis.

If you select a quad or patch of quads, straightening will align the quads to the grid and unwrap the remainer of the island around the straightened section. If the quads form a continuous ring, straightening will automatically add a split so that it can be unwrapped as a straight line.

If you your selection contains a triangle or an n-gon, straightening will align the bounds of the selection to the grid and unwrap the remainder of the island around the aligned section.