Kobbelt and Butterfly subdivision schemes for grasshopper added in Yellow plugin .
Kobbelt and Butterfly unlike other two popular subdivision schemes (Loop and Catmull Clarck) add volume to geometry instead of increasing it in order to refine . Kobbelt scheme was found by Leif P. Kobbelt in 1996 and Butterfly was a work of Dyn, Gregory and Levin in 1990.