This 2010 paper on blending showed up in my google searches.
Possibly it would be of interest, or has already been read?

Gn blending multiple surfaces in polar coordinates

https://hal.archives-ouvertes.fr/inria-00517941/document

- Brian

One more search link:
http://scholar.google.com/scholar?hl=en&q=Kan-Le+Shi%2C+Jun-Hai+Yong&btnG=&as_sdt=1%2C48&as_sdtp=