I learned how to use Wings3D from the sites written in Japanese (here or here). I don't know which tutorial in English I should recommend, but this site seems to have enough information.
I used ver. 1.5.1 in this example. (The latest stable release is ver 1.5.2.)
I'd like to omit explanation for basic usage of this program.
Open Wings3D and import the model of cup&saucer. (File > Import > Wavefront (.obj)... )
When importing an .obj file, group information is kept as those in Metasequoia. You can see the groups 'cup', 'handle' and 'saucer' in Geometry Graph panel.
Click 'cup' to select the cup part.
Right click at anywhere blank in Geometry window.
Commands list will appear. Right click '.UV Mapping.'.
AutoUV Segmenting window will open. In this window, segment the cup mesh for mapping.
Make sure you selected Edge selection mode, and select edges where you want to cut for mapping.
In this case, I selected the edges shown above. Dodecagon part was cut into three parts.
Here I forgot to select one edge. It was not on purpose. I'll mention how to fix it later.
Then right click anywhere blank in this window.
Select 'Mark Edges for Cut'.
Hit the space bar to deselect the edges. You can see the marked edges turned orange.
In other many modeling software, if you click blank space after selecting something, the selected parts will be deselected. But in Wings3D, the selected parts are NOT deselected by clicking blank space unless you hit space bar. It's very useful function of this software.
Right click at blank space, and select 'Continue', and then 'Unfolding'.
There are various way to map, but I use this 'Mark Edge for cut' - 'Unfolding'. This method can be used for any shape, complicated or organic forms.
AutoUV window pop up. Default texture is applied at this point.
Select a part and right click. Command list appears. Here you can select a command you like.
Move and Rotate each parts and roughly align them for convenience.
I replaced the texture to make it easy to see. To replace the default texture with another one, File > Import Image... and select your texture. You can see the new texture in Outliner panel.
Click and drag-drop it onto the AutoUV window.
Now align the vertical lines of outside surfaces of the cup. Select all the vertical edges as shown above.
Right click in blank area and select Scale > Horizontal. And slowly move mouse and stop it at the point they looks straightened.
In similar way, select all horizontal edges, Scale > Vertical to align them.
Overlay these three aligned segments.
Next, in similar way, align the edges of inside segments of the cup.
As for the center vertices, right click, select Flatten > Y. Move them in horizontal direction as shown the following picture.
You can see the edge I forgot to cut. Let's fix it now. Select the edge and right click, select Cut. And move the vertices in same way as other two segments.
Overlay three segments of inside surfaces.
The 'dead space' of UV map should be as little as possible. So scale up these segments (right click, Scale, move mouse).
I was planning to use 512px x 512px image for this object and to apply 2 x 2 patterns to it. And I wanted to make the outside texture on the cup part seamless. So I scaled up the segments to about a half of the map (about 256px) using grids of default texture as a reference.
UV-mapping of the cup group is done.
Next post will start with UV-mapping of other parts.