uMake give you the ability to create complex compound surfaces through the use of what we call closed area surfaces.
A closed area surface can be created from a single closed curve, up to four curves who's endpoints touch one another, thus creating a 'closed area'.
The curves become the edge curves of of the surface allowing for more precise control in creating a beautiful surface.
A closed area surface is the sum of the edge curves, thus it is important to create nice edge curves and practice with creating closed area surfaces to avoid getting wrinkles and other odd artifacts that can appear as a result of curves that may be too complex. For example, sharp corners sometimes create creases in a closed area surface depending on the geometry of the other curves.
To create a closed area surface, select one to four curves and make sure that their ends are all touching. If a surface can be created and all curves are touching, the curves will turn yellow to indicate a surface can in fact be created.
Once the edge curves are selected, simply tap the icon to create a surface and a surface will be created within the 4 curves.
The two images below show edge curves selected, and then the surface created between them. The entire shoe was created using closed area/ edge curves.