Align UV is a simple to for aligning UV faces to XY axis and same size.

• Align quads to global X Y Axis, with same size and good orientation
• Smoothing / Relaxing the complicated quads inland or non-quads faces to same size, relaxed alignment
• Relaxing internal faces inside a fixed island boundary.
• Smooth a edges line (smooth curve or completely straight)

Align Row-Column based UV quads :

Relaxing non-quad or irregular topology UV faces :

Relaxing Internal Faces with fixed boundary

Edges smoothing

Usage

In the Blender UV Edit page,

Switch to "Face" mode.

Right click, then you will see the Blender's pop up menu.

You will see Align UV and Align UV (smoothing) at the bottom of menu.

Align UV

Very fast algorithm for aligning quad face. The tool assume that the faces are in row / column topology.

If the quads are cross-connected (eg : 3 quads connected like a ring), the result will be problematic.

Align UV (smoothing shape)

This is a slower algorithm, but it can handle any faces (quad or ngons).

Also it can be used for smoothing quads with complicated topology, and make them even size.

Align UV (Inner Area)

This tool relax the internal faces tension and keep the boundary edges fixed. You can select a UV island (move your cursor to a UV island, then press L key in blender) , then run Align UV (Inner Area) to relax its inner faces. This tool wells better then "Align UV Smoothing" for some cases.

Tips : You can press "Shift - R" key in blender to repeat the last tool. So you can run Align UV (Inner Area) once, then hold down the Shift -R to repeat it easily.

Align UV (Edge)

This tool is used for smoothing the selected edges line. It can be inner edges or boudnary edges.
You can control the degree of smooth / stragiht by adjusting the engine loop count.

Limitations

• If you use Blender "Smart UV Project", it might be problematic.
  Because "Smart UV Project" does not generate continous UV pieces. It breaks and cuts all the surface into small pieces.
  If you use Align UV for them, Align UV will just treat each pieces independently, and turn them into small square.
  Since Align UV is not a "UV packer", it does not arrange or maximize the UV coverage.

Updates

Version 2.4.1

• Fixed a bug that cause Align UV to freeze very long time on some cases.

Version 2.4.0

• Improved the consistency and quality of Align UV (Smoothing). Now you can select some of the faces and smooth them, the face will stay at the same location.

Version 2.3.0

• Added an option for aligning to global XY axis for Align UV (Edge) tool.

Version 2.2.0

• Added a Edges Smoothing function. You can select continous edges and smooth them with different degree, It works for inner edges or boundary.

Version 2.1.0

• Added a new function "Inner Area". It is a special too for relaxing tension of inner area of the selected UV island. The boundary edges will be fixed, and the inner faces will be relaxed, they will have similar amount of area. This tool use different algorithm from "Smoothing" , and it works better especially for UV island with "holes".

Version 2.0.0

• Improved the speed of "Align UV Smoothing" mode. Also improved the quality of relaxing UV quad and Alignment.
  

Version 1.1.0

• Added the "Auto size" option and enabled by default. The tool will detect the grid size for the selected mesh automatically.

It is a free addon !

Hope that you like it : )

Kushiro

https://x.com/kushirosea