More Pivot Center options in Unwrap UVW Editor

[dswahn]

An often overseen feature of the UVW Unwrap Editor is the ability to scale from a specific point using the Set Pivot options, example:

However, there are only five options to choose from - center and the four corners. It would be highly useful to be able to set the center of each side as well, such as center top, center right, etc.

Using MAXScript such options already exist (https://help.autodesk.com/view/MAXDEV/2023/ENU/?guid=GUID-496CE46A-EBD3-40C2-9637-3F21E0F0B0FB )
<void><Unwrap_UVW>.snapPivot <integer>pos
1 is the center
2 is the lower left of the selection
3 is the lower center of the selection
4 is the lower right of the selection
5 is the right center of the selection
6 is the upper right of the selection
7 is the upper center of the selection
8 is the upper left of the selection
9 is the left center of the selection

So why not expose this to the user interface?

Manipulating the pivot manually is also very difficult, if you work in UV Polygon sub-level it is impossible to move the Pivot to a manual place since Polygons will always overlap any interaction with the Pivot. Switching to UV Vertex sub-level will not overlap the Pivot, but any switching of the sub-level instantly resets the Pivot position, which forces you to work in Vertex if you even feel like manual placement. But the risk of loosing whatever manual placement is extremely high. Therefore I suggest the following:

• Expose all 9 Pivot snap options directly in the UVW Unwrap Editor interface.
• Provide an option to stop the pivot from resetting, meaning the Pivot position will stay the same between selection changes.
• Provide and interface to set Pivot position by coordinate values for precise placement.

There also seems to be some bugs with the current system that needs to be addressed:
• When undoing it seems the Pivot does not update it's position correctly, making the Pivot drift away each time you undo:

• When changing Pivot and using the Scale spinners directly it doesn't respect the new Pivot position until you click inside the UV layout space, which is annoying.