Function representation

In computer graphics the function representation (FRep[1] or F-Rep) is used in solid modeling and volume modeling. FRep was introduced in "Function representation in geometric modeling: concepts, implementation and applications" [2] as a uniform representation of multidimensional geometric objects (shapes). An object as a point set in multidimensional space is defined by a single continuous real-valued function of point coordinates F(X) which is evaluated at the given point by a procedure traversing a tree structure with primitives in the leaves and operations in the nodes of the tree. The points with F(X) >= 0 belong to the object, and the points with F(X) < 0 are outside of the object. The point set with F=0 is called an isosurface.