interface 
BicubicGrid 
A gridded surface that uses cubic polynomial splines as the
horizontal and vertical curves.

interface 
BilinearGrid 
A gridded surface that uses line strings as the horizontal and
vertical curves.

interface 
BSplineSurface 
A rational or polynomial parametric surface that is represented by control points, basis
functions and possibly weights.

interface 
Cone 

interface 
Cylinder 
A gridded surface given as a family of circles whose positions vary
along a set of parallel lines, keeping the cross sectional horizontal curves of a constant shape.

interface 
Sphere 
A gridded surface given as a family of circles whose positions vary
linearly along the axis of the sphere, and whose radius varies in proportion to the cosine
function of the central angle.
