A surface object is a shell with an infinitesimally small thickness. Using surfaces to create the 3D model affords the advantage of using associative modeling or sculpting using the control vertices of NURBS surfaces. In the following sub-sections, we will learn how to create the two main types of surfaces available in AutoCAD, which are as follows:

• Planar surfaces
• Network surfaces

The latter has the option to be associative or to be a NURBS surface, as we will see in this section. After that, we will learn about additional surface creation commands that use the edges of existing surfaces to close gaps and holes in the model, and we will learn about the surface offset command. 

Let's now dive deeper into the first type of surface – planar surfaces.