3D Primitives and Conversions - Autodesk AutoCAD 2013 Practical 3D Drafting and Design - page 156

• Object : This option prompts for the selection of objects. We can select
lines, arcs, circles, ellipses, 2D polylines, 3D planar polylines, planar
splines, regions, and 3D faces. For each closed object or set of objects
that form a closed boundary, the option creates a surface. By default, the
original objects are maintained in the drawing.

Note

There are two important variables when creating surfaces from other objects.
SURFACEASSOCIATIVITY controls if the surface remains connected to the ori-