What is a Surface Entity?


A NURB surface entity is a flexible, membrane-like skin defined by a rectangular grid of points. The surface passes through the points and is drawn by displaying curves passing through each row and column set of grid points. These grid points are the edit points of the surface and are used to change the shape of the surface.


There are really no differences between the rows and columns of a surface, so all of the commands in the program apply to either rows or columns. Internally, the program knows which are rows and which are columns, but you should never have to know which are which. That is why many of the commands refer to both row and col.


Surfaces can be created in many ways. They can be created using the Surf-Add Surf command, by extruding a curve entity, by skinning between two or more curves, or by creating complete 3D objects made up of NURB surfaces. It is your job to determine how a complete 3D object can be pieced together from these rectangular-like NURB surfaces. There is no single way of doing this. (See the section called “How Do You Create 3D Geometry?”)